Polyphosphide Precursor for Low-Temperature Solution-Processed

Subscriber access provided by UNIV OF SOUTHERN INDIANA

Article

Polyphosphide Precursor for Low-Temperature Solution-Processed Fibrous Phosphorus Thin Films Hyeong Woo Ban, Jong Gyu Oh, Seungki Jo, Hyewon Jeong, Da Hwi Gu, Seongheon Baek, Song Yeul Lee, Yong Il Park, Jaeyoung Jang, and Jae Sung Son Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.9b02183 • Publication Date (Web): 16 Jul 2019 Downloaded from pubs.acs.org on July 24, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Chemistry of Materials

Polyphosphide Precursor for Low-Temperature Solution-Processed Fibrous Phosphorus Thin Films Hyeong Woo Ban,†,⊥ Jong Gyu Oh,‡,⊥ Seungki Jo,† Hyewon Jeong,† Da Hwi Gu,† Seongheon Baek,† Song Yeul Lee,§ Yong Il Park,§ Jaeyoung Jang,*,‡ and Jae Sung Son*,† †

School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea. ‡ Department of Energy Engineering, Hanyang University, Seoul 04763, Republic of Korea. § School of Chemical Engineering, Chonnam National University, Gwangju 61186, Republic of Korea. ABSTRACT: Crystalline red phosphorus has very recently emerged as stable and cost-effective semiconductor materials. However, despite its potentiality in electronics and optoelectronics, the widespread application of this material is still hampered by the limited synthetic route of the ampoule-based chemical vapor deposition that critically requires mineralizing agents. To address this issue, we report the chemical synthesis of soluble polyphosphide precursors that serve as inks for the solution-processed fabrication of crystalline fibrous phosphorus thin films. The purified polyphosphide precursor formed crystalline fibrous phosphorous via thermal annealing at the temperature as low as 250 °C without any mineralizing agents. This anionic polyphosphide functioned as a surface-capping ligand for nanoparticles including metals, semiconductors, and magnets. Therefore, the study investigates the possibility of solutionprocessed fibrous phosphorus thin films as active channel layers in field-effect transistors (FETs) as well as photodetectors and demonstrates their initial performances on the charge-transport and photo-responsive characteristics of these devices. The effect of semiconducting PbS nanoparticles embedded in the fibrous phosphorus thin films on device performance was also studied. The synthesized polyphosphide precursor offers a vast opportunity for the facile preparation of crystalline red phosphorus and chemical design of nanoparticles.

INTRODUCTION Phosphorus is recognized as a defining element in di-verse disciplines including chemistry, physics, agriculture, and ecology and exists as white, black, and red phosphorus allotropes. 1 Of these, white phosphorus that consists of tetrahedron P 4 molecules is the most reactive and widely utilized as a phosphorus precursor to manufacture phosphorus-containing compounds.2 Recently, another allotrope of black phosphorus that has a layered two-dimensional (2D) structure has emerged as a fascinating member of 2D materials. It exhibits high carrier mobility as well as semiconducting characteristics with a tunable and moderate direct bandgap,3 offering great potential in electronic and optoelectronic applications.4,5 However, this promising material undergoes oxidation-induced degradation under ambient conditions and requires harsh synthetic conditions with extremely high pressure,3,6,7 restricting its widespread applications. In comparison, red phosphorus is cheap, less toxic, and less sensitive to oxidation under ambient conditions, making it a promising candidate in materials science.1 Red phosphorus generally exists as an amorphous phase (Type I) comprising a polymeric phosphorus network formed by thermal conversion from white phosphorus at 250~280 °C.8 Type IV and Type V red phosphorus are crystalline, termed fibrous and Hittorf’s phosphorus, respectively. The recently explored fibrous phosphorus has parallelly aligned double tubes comprising repeated P8 and P9 cages.9 Unlike the amorphous phase of red phosphorus, recent studies reported that these crystalline red phosphorus members exhibit defined semiconducting properties with direct band gaps of 1.5 and 2.1 eV, respectively.10,11 Moreover, a theoretical study on Hittorf’s phosphorus predicts that single-layered crystalline red phosphorus shows high hole mobilities (3000–7000 cm2 V−1 s−1),10 and the recent study on a nanowire of Type IV fibrous phosphorus reported 308 cm2 V−1 s−1 of its hole mobility,12 offering great potentials as a cost-effective and

highly stable semiconductor material. Nevertheless, research on the synthesis and applications of crystalline red phosphorus are still in a very early stage and only few reports demonstrate their applicability in electronics12 or as a photocatalyst.13-15 Ruck et al. reported the iodine-catalyzed synthesis of crystalline one-dimensional (1D) fibrous phosphorus using a complicated chemical vapor deposition (CVD) method via sublimation of amorphous red phosphorus in an evacuated ampoule at ~ 590 °C for several days.9 Thereafter, most studies on fibrous phosphorus synthesis have adapted this method with catalytic mineralizing agents. For example, Eckstein et al. synthesized urchin-shaped 1D red fibrous phosphorus microwires with a mineralizing agent like CuCl2.16 Smith et al. synthesized ultralong 1D fibrous phosphorus nanowires by depositing red phosphorus with Sn/SnI4 mineralizing agents on silicon.12 However, these CVD-based syntheses require relatively high temperature and low pressure, complicated multi-step processing, and catalytic mineralizing agents to ensure crystallinity, thus requiring a new synthetic route for simple and scalable production of highly crystalline red phosphorus. For cost-effective and scalable fabrication of semicondutor thin films, solution-based deposition of inorganic materials can be applied. To date, several chemical methods to synthesize soluble inorganic precursors including chalcogenidometallates,17,18 sol-gel oxides,19,20 and so on have been proposed. Anionic inorganic ligands-capped metal or semiconductor nanoparticles,21-28 called all-inorganic nanoparticles, are precursors enabling fundamental studies on nanostructuring and/or quantum effects in solution-processed electronics and optoelectronic devices. Although these chemistries have widely extended the available inorganics for solution-processed deposition, studies on soluble precursors for single element materials including phosphorus have rarely been reported owing to the lack of syn-

ACS Paragon Plus Environment

Chemistry of Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

thetic routes. Herein, we present novel chemistry for the synthesis of soluble polyphosphide precursors that serve as inks for solution-based fabrication of crystalline fibrous phosphorus thin films. The purified polyphosphide precursor shows excellent solubility in polar solvents and good coatability with common solution-casting methods, enabling fibrous phosphorus thin film fabrication after mild heat treatment at 250 °C without mineralizing agents. In addition, the anionic polyphosphides were successfully utilized as surface-capping ligands for various colloidal nanoparticles such as semiconductors, metals, and magnets. The possible application of fibrous phosphorus thin films as active channel layers in field-effect transistors (FETs) and their initial performances on charge-transport and photoresponsive characteristics were investigated. The synthesized polyphosphide precursor gives a vast opportunity for not only a facile preparation of crystalline red phosphorus but also chemical design of nanoparticle surfaces.

EXPERIMENTAL SECTION Chemicals. Potassium ethoxide (KOEt, 95%, Aldrich), red phosphorous powder (Pred, -100 mesh, 98.9%, Alfa Asear), 1,2dimethoxyethane (DME, anhydrous, 99.5%, Aldrich), tetrahydrofuran (THF, anhydrous, 99.9%, Aldrich), ethyl alcohol (EtOH, anhydrous, ≥99.5%, Aldrich), hexane (anhydrous, 95%, Aldrich), chloroform (CHCl3, 99.5%, Samchun), n-methylformamide (NMF, 99%, Aldrich), ethylenediamine (En, ≥99.5%, Aldrich), dimethyl sulfoxide (DMSO, anhydrous, ≥99.9%, Aldrich), formamide (FA, 99.5%, Alfa Aesar), n,n-dimethylformamide (DMF, anhydrous, 99.8%, Alfa Aesar), isopropanol (IPA, 99.5%, Samchun), cadmium oxide (CdO, 99.99%, Aldrich), trioctylphosphine oxide (TOPO, 99%, Aldrich), octadecylphosphonic acid (ODPA, 97%, Aldrich), selenium (powder, 99.99%, Aldrich), trioctylphosphine (TOP, 90%, Aldrich), gold(III) chloride trihydrate (HAuCl4∙3H2O, 99.9%, Aldrich), 1,2,3,4-tetrahydronaphthalene (tetralin, 97%, Alfa Aesar), oleylamine (OAm, approximate C18-content 80-90%, Acros organics), borane tert-butylamine complex (TBAB, 97%, Aldrich), indium(III) chloride (99.999%, Aldrich), zinc(II) chloride (≥98%, Aldrich), tris(diethylamino)phosphine (97 %, Aldrich), oleic acid (OA, 90%, Aldrich), sulfur (99.998%, Aldrich), lead(II) chloride (PbCl2, reagent grade 99%, Alfa Aesar), iron(III) acetylacetonate (97%, Aldrich), platinum(II) acetylacetonate (97%, Aldrich), 1,2-hexadecanediol (technical grade, 90%, Aidrich), gadolinium acetate hydrate (99.9%, Aldrich), erbium acetate hydrate (99.9%, Aldrich), ytterbium acetate hydrate (99.9%, Aldrich), sodium hydroxide (97%, Aldrich), ammonium fluoride (99.9%, Aldrich), methanol (99.9%, Daejung), 1-octadecene (ODE) (>90%, Aldrich), and dioctyl ether (99%, Aldrich). All other chemicals were used as received without further purification. Synthesis of polyphosphide precursors. The polyphosphide precursors were synthesized according to the published literature with slight modifications.29 All manipulations for the synthesis of the initial polyphosphide precursors were performed under inert N2 atmosphere by standard schlenk techniques, or in N2 filled glovebox. At first, 3.2 mmol of KOEt and Pred were added in a 100 mL of three neck round bottom flask. Then, the mixture was dissolved in DME/THF (3.0 mL; 1:1 v/v). The suspension was heated from room temperature (RT) to 85 °C for 5 min with a heating rate of 12 °C min−1. At that temperature, reflux by cold water was performed for 3 h with continuous stir-

Page 2 of 10

ring. After cooling it to RT, N2 flowed enough to remove residual solvents for dryness of resulting suspension and 6 mL of anhydrous EtOH was injected into the flask. The dissolved dark-red suspension in EtOH was separated into supernatant and precipitate by centrifugation (13400 rpm, 5 min) in N2 filled glovebox. The supernatant acquired from the crude solution was precipitated by the addition of CHCl3 (1:3 v/v), followed the centrifugation (7800 rpm, 5 minutes). The purified polyphosphide precursors were dissolved in 6 mL of NMF and repurified by the addition of 12 mL of IPA. For effective removal of byproducts, the purifying process by IPA can be repeated and finally they were dissolved in En or NMF and stored in N2 filled glovebox for further experiments. Cation exchange reaction. Cation exchange was conducted by ion-exchange resins. In N2-filled glovebox, the 30 mg of NH4+resin beads prepared by mixing the acidic resin beads having H+ as cation with an aqueous solution of NH4Cl was added to a 1.0 mL of purified polyphosphides solution in NMF with K+ as counterions. The mixture was vigorously vortexed for 10~15 min, and the solution was separated from the resin beads by centrifugation (13400 rpm, 5 min). The polypshophides solution with NH4+ as counterions was retrieved by adding toluene to the solution, followed by centrifugation. This procedure also repeated three times and finally, precipitates were dissolved in 0.5 mL of NMF, making a stable ammonium polyphosphides solution. Synthesis of organics-capped nanoparticles. CdSe nanoparticles (3.5 nm-sized) and InP nanoparticles (2.7 nm-sized) were synthesized according to the same experimental procedure reported by Ban et al. and Tessier et al., respectively.25,30 Au nanoparticles (6.0 nm-sized) were synthesized according to the recipe developed by Zhu et al. with slight adjustments.31 Here, under the N2 atmosphere, the 0.2 g of HAuCl4 was dissolved in 20 mL of tetralin and OAm mixture (1:1 v/v) at only RT during 1 h. FePt nanoparticles (2.5 nm-sized) were synthesized following the published literature by Liu et al. except for using a dioctyl ether instead of an octyl ether.32 PbS nanoparticles (6.7 nm-sized) were synthesized following the experimental procedure reported by Weidman et al. with slight alterations.33 Sulfur precursor solution was heated by using a heating mantle with a heating rate of 5 °C min−1 for 20 min. NaGdF4:Yb,Er nanoparticles (10.0 nm-sized) were prepared according to reported procedure with minor modification.34 In detail, gadolinium acetate hydrate (0.78 mmol), ytterbium acetate hydrate (0.20 mmol), and erbium acetate hydrate (0.02 mmol) were added into a three-necked flask containing OA (10 mL) and ODE (15 mL). The mixture was heated to 150 °C and kept it for 40 min, and then cooled to RT. Sodium hydroxide (2.5 mmol) and ammonium fluoride (4.0 mmol) were dissolved in methanol, respectively. Each methanol solution was added to the reactor and stirred for 30 min at 50 °C. Then, the mixture was heated to 110 °C under vacuum with stirring for 15 min to remove methanol. The flask was switched to Ar atmosphere and the temperature was raised to 310 °C at a rate of 10 °C min −1 and maintained for an hour. Finally, the reactor was cooled to RT, and the nanoparticles were precipitated by addition of ethanol and recovered by centrifugation. The product was dispersed in hexane and stored in refrigerator. Ligand exchange reaction for various colloidal nanoparticles with polyphosphides anions. All surface modification processes were carried out in N2 filled glovebox. In a typical two-phase ligand exchange process, 0.5 mL of nanoparticles in


Page 3 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


hexane (20 mg mL−1) was placed into a vial containing 1.5 mL of polyphosphides dissolved in NMF (70 mg mL−1), resulting in a formation of upper hexane phase and bottom NMF phase. This immiscible two-phase mixture was performed under vigorous stirring until complete phase transfer of nanoparticles from the upper nonpolar phase to bottom polar phase. After ligand exchange, upper colorless hexane was fully discarded. To purify nanoparticles, the remained bottom solution containing polyphosphides-capped inorganic nanoparticles was precipitated by the addition of 1.5 mL of IPA, followed the centrifugation (13400 rpm, 5 min). The precipitated nanoparticles capped with polyphosphides were dispersed in 1 mL of fresh NMF for further experiments. Mixed solution of polyphosphide with nanoparticles. Solutions for pure fibrous phosphorus thin films were prepared by purified polyphosphide precursors dissolved in En or NMF (200 mg mL−1). Inks for PbS-nanoparticle-embedded fibrous phosphorus thin films were prepared by polyphosphides-capped PbS nanoparticles solutions with excess polyphosphide ligands. In detail, ligand exchange reaction proceeds in the combination of 40 mg of PbS nanoparticles in hexane (15 mg mL−1) and 150 mg of purified polyphosphides in NMF (50 mg mL−1). After ligand exchange, both polyphosphides-capped PbS nanoparticles and polyphosphide ligands in NMF were precipitated by a large excess amount of IPA to concentrate the solution to a high concentration. Then, the precipitates were dispersed in 0.5 mL of fresh NMF to use as inks. Device fabrication. Heavily doped n-type Si wafers covered with a thermally grown SiO2 layer (100 nm) were used as gate substrates. To form source/drain (S/D) electrodes, Ti/Au (7/40 nm) were thermally evaporated on the substrates and photolithographically patterned into interdigitated contacts with various pairs of channel lengths (L) and widths (W) (W/L = 13200 µm/3 µm, 7800 µm/5 µm, and 3800 µm/10 µm). The substrates with S/D electrodes were cleaned in acetone, rinsed with IPA, and blown with N2 before use. Solutions for pure fibrous phosphorus thin films and PbS nanoparticle-embedded fibrous phosphorus thin films were spin-coated onto the cleaned substrates. The spin-coated films were pre-baked at 100 °C for 20 s on a hotplate to evaporate residual solvents and then annealed at 250 °C for 30 min. All device fabrication procedures were performed in a N2 filled glove box. Material characterization. Electrospray ionization mass spectrometry (ESI-MS) data were recorded on a JEOL JMS-T100LP AccuTOF LC-plus time-of-flight (TOF) mass spectrometer. The instrument was calibrated with dithranol for accurate mass analysis. Microstructural characterization was carried out by employing a Nova-NanoSEM230, FEI scanning electron microscopy (SEM) operated at 10 kV. The Raman spectra were acquired using a Witec alpha 300R confocal Raman microscope with 532 nm laser wavelength and 0.7 mW of excitation power. High-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) pattern were collected using a JEOL JEM-2100F microscope operating at 200 kV. For the preparation of the HRTEM specimens, the powder form of heat-treated polyphosphides was carefully dropped onto TEM grids coated with carbon film. TEM images of nanoparticles were obtained using a JEOL-2100 instrument accelerated at 200 kV. TEM specimens for nanoparticles dispersed in various solvents were prepared by drop-casting on carbon-coated copper TEM grids and fully dried under vacuum chamber. UV–Vis absorption spectra of nanoparticle solutions

were acquired at RT using a Shimadzu UV–2600 spectrophotometer. The optical photoluminescence (PL) spectra were obtained using a Cary Eclipse fluorescence spectrophotometer. UV–Vis absorption and diffuse reflectance spectra of red phosphorus thin films were measured using a Cary 5000 UV–Vis– NIR spectrophotometer. Analysis of trace element composition was conducted by inductively coupled plasma optical emission spectrometry (ICP-OES) using a Varian 700-ES. Fourier transform infrared spectroscopy (FT-IR) spectra were obtained in attenuated total reflectance (ATR) mode using a 670/620 Varian FT-IR spectrometer. High power x-ray diffraction (HPXRD) patterns were collected at RT using a Rigaku D/Max2500V diffractometer equipped with a Cu-rotating anode X-ray source. ζpotential data were obtained using a Malvern Zetasizer NanoZS90. Device characterization. All electrical and optoelectrical measurements were performed using a Keithley 4200 semiconductor parameter analyzer in a N2 filled glove box. Field-effect mobilities were extracted in the saturation regime and calculated using the following equation: ID = μCi(W/2L)(VG - Vth)2, where Ci is the capacitance per unit area (30.0 nF cm−2) and Vth is the threshold voltage. For photoresponse measurements, the devices were exposed to white light (100 mW cm−2) in dark condition and electric currents were measured. The responsivity (R) values were extracted from the photocurrent (i.e. the difference of ID before and after light exposure; Iph = ID, light-on – ID, light-off ) divided by the incident light power on the active area of the device (Pin(Aactive/Aspot)), where Pin is the total power of the light source, Aactive is the active area of an FET, and Aspot is the total area of the light spot exposed on the substrate (see Figure S9 for schematic explanation of Aactive).

RESULTS AND DISCUSSION

Figure 1. (a) Schematic illustration showing the preparation for polyphosphide inks and fabrication of fibrous phosphorus thin film by solution-process. (b) Photograph of the polyphosphides precursor solution dissolved in polar solvents: dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), ethylenediamine, formamide (FA), and n-methylformamide (NMF). (c) ESI-MS spectrum of purified polyphosphides precursor solution in negative ionization mode.

Figure 1a schematizes the synthesis of polyphosphide precursor solution and solution-based fabrication of fibrous phosphorus thin films. For initial polyphosphide-precursor synthesis, the reported chemical route29 was modified, wherein amor-



phous red phosphorus reacted with potassium ethoxide to produce potassium mixtures of polyphosphides powder. To eliminate any possible unreacted precursors and byproducts, the assynthesized polyphosphide powder was further purified by dispersing it in ethanol and removing the insoluble precipitates. This step is crucial to obtain high-purity polyphosphide precursors. The purified precursor was easily solubilized in various polar solvents (Figure 1b). The electrospray ionization mass spectrum of the purified precursor solution in dimethyl sulfoxide (DMSO) in negative ionization mode shows multiple peaks in the mass-to-charge ratio (m/z) range of 150–500 (Figure 1c). Among the possible forms of polyphosphides, including the peak at 496.5 m/z, peaks of fragmented species corresponding to the value for (HP16)− were clearly observed. This P162− dianion is reported to form two nortricyclene P7 cages connected by a P2 dumbbell.29

Figure 2. (a) SEM image of fibrous red phosphorus thin film annealed at 250 °C. The inset in the panel (a) shows the photograph of the thin film on a Si/SiO2 substrate. (b) UV–Vis absorption spectra of polyphosphide precursor solution (black), as-dried (blue), and heat-treated (red) phosphorus thin films at 250 oC. (c) Raman spectra of fibrous red phosphorus thin films deposited on glass (black) or Si/SiO2 (red) substrates. The bottom vertical lines show peaks from references for type IV 35 and V12. (d) HRTEM image of solution-processed fibrous red phosphorus (the inset in the panel (d) shows the corresponding SAED pattern).

We analyzed the chemical composition of the synthesized potassium polyphosphides by inductively coupled plasma optical emission spectrometers (ICP-OES). The ratio of K:P in the synthesized polyphosphide precursors dissolved in DMOS was 1:8.5, agreeing with the expected structures of K2P16 from ESIMS spectrum. However, their solution in different solvents of n,n-dimethylformamide (DMF) and n-methylformamide (NMF) exhibited the ratio of K:P of 1:15 and 1:16.6, respectively. At the same time, we found that the solubility of polyphosphides precursors was changed in alcoholic solvents when it was dispersed in DMF or NMF. This might be attributed to the replacement of K+ with DMF and NMF as the formamidinium cation. To demonstrate this hypothesis, we tried to replace K+ with ammonium using ion-exchange resin beads and observed a threefold reduction in the content of K in polyphosphides. These results lead us to conclude that the counter balance cation of K+

Page 4 of 10

in polyphosphides is replaceable with possible cations of ammonium or formamidinium, rather than the change of molecular structures. The polyphosphides ink solutions were spin-coated or drop casted on glass substrates or Si/SiO2 wafers, followed by thermal annealing for 30 min. The scanning electron microscopy (SEM) image in Figure 2a demonstrates the dense and continuous microscale morphology of the polyphosphide film annealed at 250 ℃. The inset in Figure 2a shows the even greenish color of the entire film on a Si/SiO2 substrate, indicating its good coverage and uniform thickness. The optical properties of as-dried and heat-treated phosphorus thin films at 250 oC were characterized by UV–Vis absorption spectroscopy (Figure 2b). The heat-treated fibrous phosphorus thin film’s UV–Vis absorption spectrum shows strong exciton absorption features in the entire visible range from 700 nm. Owing to the polyphosphide precursor’s absorption band from ~450 nm, this optical band shift should result from crystalline phase formation by the polymeric phosphorus network. The as-dried film’s absorption band started from ~500–550 nm, suggesting the induction of crystalline phase formation by heat treatment. The optical band gap obtained by Kubelka-Munk function plot converted from the diffuse reflectance spectrum of the heat-treated thin film was estimated to be ~1.8 eV, higher than that of bulk fibrous phosphorus (1.5 eV) (Figure S1).11 This increase may be attributed to the partial existence of Hittorf’s phosphorus (band gap of 2.1 eV) in the thin film.10 The structural evolution of this thin film upon heating was analyzed via Raman spectroscopy. The polyphosphide precursor thin films were annealed at 100 oC~300 oC for 30 min. Above 300 oC, the quality of the film was significantly degraded by the sublimation of red P.36 As shown in Figure S2, the Raman spectra of films annealed below 250 oC show the peaks matching to those of the reported amorphous red P.14,37 On the other hand, at 250 oC and 300 oC, the Raman spectra clearly show the peaks corresponding to those of Type IV fibrous phosphorus. Also, the Raman spectra for the films prepared both on glass and Si/SiO2 substrates show identical defined peaks (Figure 2c); however, the possibility Type V formation cannot be excluded because both Type IV and Type V have very similar Raman spectra.12,14,35 The strong peaks at 353 and 368 cm−1 can be indexed with the stretching vibrations of the P8 and P9 cages, respectively.12,14,35 Note that the films deposited on glass and Si/SiO2 substrates showed almost identical Raman signals, suggesting that fibrous phosphorus formation is mainly governed by the precursor itself rather than the interaction between the precursor and substrate, unlike previous reports where CVDgrown crystalline phosphorus was exclusively grown on only Si/SiO2 substrates.12,13,35 The high-resolution transmission electron microscopy (HRTEM) image in Figure 2d shows clear lattice fringes of phosphorus, suggesting its high crystallinity. Moreover, the selected area electron diffraction (SAED) pattern includes numerous diffraction rings along which the diffraction peaks of fibrous phosphorus are observed, 11,16 indicating the polycrystalline nature of our synthesized precursor (the inset of Figure 2d).


Page 5 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Chemistry of Materials feasibility of the current polyphosphide anion as a capping ligand was demonstrated by the typical two-phase ligand exchange reaction of polyphosphide in solution with various colloidal nanoparticles: metallic Au, semiconducting InP, CdSe, and PbS, magnetic FePt, and luminescent NaGdF4:Yb,Er upconverting nanoparticles (Figure 3b).25,30-34 The polyphosphide anions performed all expected surface ligands functions. That is, all polyphosphides-capped nanoparticles showed good colloidal stabilities in polar solvents; while preserving their primary structures, as demonstrated by TEM analysis (Figure 3c-h and S3).

Figure 4. (a) Absorption and (b) PL spectra of (black) organicsand (red) polyphosphides-capped CdSe nanoparticles and (blue) polyphosphide precursor solution. (c) FT-IR spectra of organicsand polyphosphides-capped nanoparticles of CdSe, FePt, PbS, InP, and Au. (d) ζ-potential distribution of polyphosphides-capped FePt, PbS, and CdSe nanoparticles and polyphosphide precursor solution.

Figure 3. (a) Scheme for the ligand exchange process of nanoparticles with inorganic polyphosphide ligands. (b) Photographs showing the two-phase ligand exchange reaction for Au nanoparticles and the produced polyphosphides-capped Au, InP, CdSe, PbS, FePt, and NaGdF4:Yb,Er nanoparticles dispersed in n-methylformamide. TEM images of polyphosphides-capped nanoparticles: (c) Au, (d) InP, (e) CdSe, (f) PbS, (g) FePt, and (h) NaGdF 4:Yb,Er.

Molecular inorganic anions such as chalcogenidometallates, metal-free anions, and polyoxometallates have actively been utilized as surface-capping ligands for various nanoparticles.2128 These ligands electrostatically stabilize nanoparticle surfaces by providing negative charges on the surfaces, allowing colloidal stabilities of nanoparticles in polar solvents (Figure 3a). The

The absorption spectra of CdSe and InP nanoparticles hardly changed after ligand exchange, with slight blue shifts of excitonic peaks for 1S(e)–1S3/2(h) transition (Figure 4a and S4). Also, we investigated the photoluminescence (PL) characteristics of polyphosphides and CdSe nanoparticles before and after the ligand exchange. Interestingly, we found that polyphosphides showed the broad PL characteristics with the peak at 420 nm in the spectrum (Figure 4b), which matches to the position of their absorption band at 350 nm~450 nm, indicating the excitonic transition across their energy states. Such the PL characteristics are directly reflected the PL property of polyphosphides-capped CdSe nanoparticles (Figure 4b), which exhibited both peaks matching to the emission of organics-capped CdSe nanoparticles and that of polyphosphides. Also, the notable band broadening in the PL spectrum of polyphosphides-capped CdSe nanoparticles was not observed, while the slight blue-shift of the PL peak of CdSe nanoparticles was observed, agreeing with the change of the absorption spectrum after the ligand exchange (Figure 4a). Identical X-ray diffraction patterns were obtained before and after ligand exchange (for Au and CdSe nanoparticles) without any peak for other byproducts or impurities (Figure S5). Fourier-transform infrared (FT-IR) spectra revealed that the ligand exchange of CdSe nanoparticles with polyphosphide anions caused the complete disappearance of the bands corresponding to the C–H stretching modes (2700–3000



Page 6 of 10

cm−1), but clearly observed in organic-ligand-capped nanoparticles (Figure 4c). Polyphosphides-capped PbS, FePt, InP, and Au nanoparticles showed similar FT-IR spectra tendencies (Figure 4c and S6). Figure 4d shows the zeta (ζ)-potential distribution of the polyphosphide precursor and -capped FePt, PbS, and CdSe nanoparticles. As expected, the ζ-potential of the precursor solution was −39.1 mV. Similarly, all nanoparticles capped with polyphosphides exhibited negative ζ-potentials regardless of the core materials, supporting successful ligand exchange on the surfaces.

Figure 6. (a) Time-dependent photocurrent of FET with fibrous red phosphorus thin film with and without white-light exposure (incident light power: 100 mW cm−2). The inset in panel (a) shows the schematic of selectively photo-exposed FETs with fibrous red phosphorus thin film. (b) ID vs VG curves of pure and polyphosphides-capped PbS-nanoparticles-containing fibrous red phosphorus thin films before and after white-light exposure. (c) Photoresponsivity of pure and polyphosphides-capped PbS-nanoparticlescontaining fibrous red phosphorus thin films. The inset in figure 6c shows the schematic diagram of fibrous phosphorus thin films containing polyphosphides-capped PbS nanoparticles under whitelight exposure. (d) Band alignment at the junction of fibrous phosphorus and PbS nanoparticles.

Figure 5. (a) Schematic and optical microscope image of FETs used herein. (b) Transfer (ID vs VG) and (c) output (ID vs VD)

characteristics of FETs with fibrous red phosphorus thin film. Finally, the electronic and optoelectronic properties of the fibrous phosphorus thin films were investigated by fabricating bottom-contact, bottom-gate FETs (Figure 5a). The capability of the polyphosphides as capping ligands of all-inorganic nanoparticles enabled the fabrication of nanoheterostructured fi

brous phosphorus thin films embedded with nanoparticles without any possible organic impurities. Therefore, the fundamental charge-transport properties of pure fibrous phosphorus thin films and the synergistic effect between fibrous phosphorus and semiconductor nanoparticles on device performances could be studied. The Raman spectrum of fibrous phosphorus thin films containing polyphosphides-capped PbS nanoparticles (Figure S7) corresponds to that of fibrous phosphorus, indicating no negative effect of nanoparticle inclusion on fibrous phosphorus formation with thermal annealing. Furthermore, compared with the organics-capped PbS nanoparticle thin film, the excitonic peaks of the fibrous phosphorus thin film containing PbS nanoparticles in absorption spectrum were hardly changed in the range of 1000~2000 nm in wavelength, which demonstrates no degradation of nanoparticle after thermal annealing (Figure S8). Figure 5b and 5c show the transfer (drain current (ID) and (ID)1/2 vs gate voltage (VG)) and output (ID vs drain voltage (VD)) characteristics of FETs with fibrous phosphorus thin film as the active layer, respectively. Both curves show obvious n-type gate effects with an average on/off ratio of 3.1 × 10 3 and good linear/saturation behavior, suggesting the potential of the solutionprocessed fibrous phosphorus as an active material in electronic devices. To the best of our knowledge, this is the first report of n-type semiconducting properties of crystalline red phosphorus; only a few previously reported vacuum-grown red phosphorus


Page 7 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


exhibited p-type behavior.11,12,15 The reason for n-type semiconducting behavior of our fibrous phosphorus thin films might be attributed to the doping of fibrous phosphorus by a small amount of residual potassium in the films, similar to previous studies on black phosphorus.38,39 The carrier mobility of the fibrous phosphorus thin films was 1.8 × 10 −6 cm2 V−1 s−1.. Such a relatively low mobility may originate from the inferior crystallinity and film quality of the samples than high-temperature and vacuum-processed crystalline red phosphorus.40 However, the charge-transport property can be significantly improved by optimizing the processing conditions for film deposition, thermal annealing, and device fabrications. The photoresponse of the fibrous phosphorus thin films with white-light exposure (incident power of 100 mW cm−2) was investigated using the same FET architecture (Figure 6a). The current sharply increases under light exposure and abruptly decreases without light exposure, showing evident photoresponse. The effects of semiconductor nanoparticle inclusion in fibrous phosphorus thin films on the photoresponse properties were studied by fabricating FETs using nanoheterostructured polyphosphides-capped PbS-nanoparticle-containing fibrous phosphorus thin films as the active layer. Figure 6b shows the ID vs VG curves of pure and PbS-nanoparticle-embedded fibrous phosphorus thin films before and after white-light exposure. Introducing PbS nanoparticles significantly increased the photocurrents and dark currents. However, considerably enhanced photoresponsivity could be expected by nanoparticle inclusion owing to the substantial difference between the photocurrents and dark currents in the PbS-nanoparticle-embedded fibrous phosphorus thin film compared with that in the pure fibrous phosphorus thin film. Therefore, the responsivity (R) value of the fibrous phosphorus thin film embedded with PbS nanoparticles were increased to 4.24 mA W−1 by six-fold compared with 0.71 mA W−1 of the pure fibrous phosphorus thin film (Figure 6c). This increase of the photo-responsivity is attributable to the efficient transfer of photo-generated electrons from PbS nanoparticles to fibrous phosphorus, as seen in the band alignment of fibrous phosphorus and PbS nanoparticles (Figure 6d). 41-44 At the same time, this p-n junction-like band alignment may cause trapping of holes in the PbS nanoparticles, eventually preventing from the electron-hole recombination. This proposed mechanism of photogenerated electron injection has been reported in various hybrid semiconductors with similar band alignment; e.g. the combinations of PbS nanoparticles with fullerene, graphene, MoS2, etc.45-47 Additionally, the increased absorption cross-section of the fibrous phosphorus thin film by including PbS nanoparticles may increase the number of generated photo-carriers, contributing to increase the photo-responsivity. To further extend this study with diverse sets of nanoparticles beyond PbS, we fabricated the FET devices with nanoheterostructured fibrous phosphorus thin films containing polyphosphides-capped CdSe and InP nanoparticles. Unfortunately, we could not obtain meaningful transfer characteristics from the FET devices (Figures S10c and S10d). In detail, the drain currents (ID) of the devices were similar or even lower than the gate currents (IG), indicating no effective charge transports across the FET channels between source and drain electrodes. We speculate that the unsatisfactory FET performances originated from the large energy level differences between the LUMO levels of fibrous phosphorus and CdSe or InP nanoparticles. As we can see in Figure S10b, the LUMO levels of CdSe and InP nanoparticles are generally much deeper than that of PbS nano-

particles.48-51 Therefore, the band alignments of fibrous phosphorus and CdSe and InP nanoparticeles might be inferior than that between fibrous phosphorus and PbS nanoparticles. The large energy barrier may prevent efficient electron transports in the nanoheterostructured fibrous phosphorus thin films containing polyphosphides-capped CdSe and InP nanoparticles. Our speculation can be supported by many of previous literatures which emphasized the importance of an appropriate band alignment and low energy barrier in heterostructured thin films for efficient charge transports.52-54 CONCLUSION In summary, soluble polyphosphide was synthesized as a precursor for fabricating crystalline fibrous phosphorus thin films by a solution process. The as-synthesized potassium mixtures of polyphosphides powder were purified to obtain polyphosphide precursors, the solution of which formed a continuous film on various substrates via spin-coating. After thermal annealing at 250 °C, a crystalline fibrous phosphorus thin film was formed without mineralizing agents, as evidenced by Raman and TEM analyses. Moreover, this polyphosphide anion functioned as a surface-capping ligand for various nanoparticles, enabling nanoparticle dispersion in polar solvents in electrostatic stabilization without negatively affecting the nanoparticle’s primary structural and electronic properties. The charge transport and photo-responsive characteristics of the fabricated fibrous phosphorus were investigated in the FET configuration and it exhibited clear n-type semiconducting properties and remarkable photocurrent. Moreover, using mixed solutions of polyphosphides-capped PbS nanoparticles and polyphosphide, PbS-nanoparticle-embedded nanoheterostructured fibrous phosphorus thin films were fabricated, thus enhancing device performance. The developed polyphosphide precursor shows great potential in cost-effective and high-performance crystalline red phosphorus semiconductor synthesis. Furthermore, this initial study of the synergistic effect of red phosphorus and semiconductor nanoparticles on their electronic and optoelectronic properties can open a new avenue for future research on solution-processed nanostructured thin films.

ASSOCIATED CONTENT Supporting Information. Kubelka-Munk function plot of solution-processed fibrous phosphorus thin film, temperature-dependent Raman spectra, Absorption spectra of InP nanoparticles, TEM images and FT-IR spectra of organics-capped nanoparticles, comparison of XRD pattern before and after ligand exchange to CdSe and Au nanoparticles, Raman spectrum of fibrous phosphorus thin film containing polyphosphides-capped PbS nanoparticles, UV–vis absorption spectra of organics-capped PbS nanoparticle thin film and fibrous phosphorus thin film containing polyphosphidescapped PbS nanoparticles, schematic image showing interdigitated source/drain electrodes of an FET device, band alignment at the junction of fibrous phosphorus and various nanoparticles, transfer characteristics of FETs with nanoheterostructured fibrous phosphorus thin films containing polyphosphides-capped CdSe and InP nanoparticles. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION



Corresponding Author *E-mail: [email protected] (J. Jang) and [email protected] (J. S. Son)

Author Contributions ⊥H.W.B.

and J.G.O equally contributed to this work.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT J.S.S. acknowledges the Nano·Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (NRF2018M3A7B8060697) of Republic of Korea. J.J. acknowledges the Energy Demand Management Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 2018201010636A). Y.I.P was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Science, ICT & Future Planning) (No. 2016R1A4A1012224). D.H.G was supported by NRF(National Research Foundation of Korea) Grant funded by Korean Government (NRF-2018H1A2A1062416)-Global Ph.D. Fellowship Program.

REFERENCES (1) (2) (3)

(4)

(5)

(6) (7)

(8) (9)

(10)

(11)

(12)

(13)

Corbridge, D.E.C. Phosphorus: Chemistry, Biochemistry and Technology, 6th ed.; CRC Press: Boca Raton, 2013. Scheer, M.; Balazs, G.; Seitz, A. P4 Activation by Main Group Elements and Compounds. Chem. Rev. 2010, 110, 4236-4256. Liu, H.; Du, Y.; Deng, Y.; Ye, P. D. Semiconducting Black Phosphorus: Synthesis, Transport Properties and Electronic Applications. Chem. Soc. Rev. 2015, 44, 2732-2743. Li, L.; Yu, Y.; Ye, G. J.; Ge, Q.; Ou, X.; Wu, H.; Feng, D.; Chen, X. H.; Zhang, Y. Black Phosphorus Field-Effect Transistors. Nat. Nanotechnol. 2014, 9, 372-377. Xia, F.; Wang, H.; Jia, Y. Rediscovering Black Phosphorus as an Anisotropic Layered Material for Optoelectronics and Electronics. Nat. Commun. 2014, 5, 4458. Bridgman, P. W. Two New Modifications of Phosphorus. J. Am. Chem. Soc. 1914, 36, 1344-1363. Endo, S.; Akahama, Y.; Terada, S.-i.; Narita, S.-i. Growth of Large Single Crystals of Black Phosphorus under High Pressure. Jpn. J. Appl. Phys. 1982, 21, L482-L484. Roth, W. L.; DeWitt, T. W.; Smith, A. J. Polymorphism of Red Phosphorus. J. Am. Chem. Soc. 1947, 69, 2881-2885. Ruck, M.; Hoppe, D.; Wahl, B.; Simon, P.; Wang, Y.; Seifert, G. Fibrous Red Phosphorus. Angew. Chem., Int. Ed. 2005, 44, 76167619. Schusteritsch, G.; Uhrin, M.; Pickard, C. J. Single-Layered Hittorf's Phosphorus: A Wide-Bandgap High Mobility 2D Material. Nano Lett. 2016, 16, 2975-2980. Hu, Z.; Yuan, L.; Liu, Z.; Shen, Z.; Yu, J. C. An Elemental Phosphorus Photocatalyst with a Record High Hydrogen Evolution Efficiency. Angew. Chem., Int. Ed. 2016, 55, 9580-9585. Smith, J. B.; Hagaman, D.; DiGuiseppi, D.; Schweitzer-Stenner, R.; Ji, H. F. Ultra-Long Crystalline Red Phosphorus Nanowires from Amorphous Red Phosphorus Thin Films. Angew. Chem., Int. Ed. 2016, 55, 11829-11833. Shen, Z.; Hu, Z.; Wang, W.; Lee, S. F.; Chan, D. K.; Li, Y.; Gu, T.; Yu, J. C. Crystalline Phosphorus Fibers: Controllable Synthesis and Visible-Light-Driven Photocatalytic Activity. Nanoscale 2014, 6, 14163-14167.

Page 8 of 10

(14) Zhou, H.; Xu, S.; Zhang, D.; Chen, S.; Deng, J. One Step In Situ Synthesis of Core-Shell Structured Cr2O3:P@Fibrous-Phosphorus Hybrid Composites with Highly Efficient Full-Spectrum-Response Photocatalytic Activities. Nanoscale 2017, 9, 3196-3205. (15) Wang, F.; Ng, W. K. H.; Yu, J. C.; Zhu, H.; Li, C.; Zhang, L.; Liu, Z.; Li, Q. Red Phosphorus: An Elemental Photocatalyst for Hydrogen Formation from Water. Appl. Catal., B 2012, 111-112, 409-414. (16) Eckstein, N.; Hohmann, A.; Weihrich, R.; Nilges, T.; Schmidt, P. Synthesis and Phase Relations of Single-Phase Fibrous Phosphorus. Z. Anorg. Allg. Chem. 2013, 639, 2741-2743. (17) Mitzi, D. B.; Kosbar, L. L.; Murray, C. E.; Copel, M.; Afzali, A. High-Mobility Ultrathin Semiconducting Films Prepared by Spin Coating. Nature 2004, 428, 299-303. (18) Heo, S. H.; Jo, S.; Kim, H. S.; Choi, G.; Song, J. Y.; Kang, J. Y.; Park, N. J.; Ban, H. W.; Kim, F.; Jeong, H.; et al. Composition Change-Driven Texturing and Doping in Solution-Processed SnSe Thermoelectric Thin Films. Nat. Commun. 2019, 10, 864. (19) Spanhel, L.; Anderson, M. A. Semiconductor Clusters in the SolGel Process: Quantized Aggregation, Gelation, and Crystal Growth in Concentrated Zinc Oxide Colloids. J. Am. Chem. Soc. 1991, 113, 2826-2833. (20) Livage, J.; Henry, M.; Sanchez, C. Sol-Gel Chemistry of Transition Metal Oxides. Prog. Solid State Chem. 1988, 18, 259-341. (21) Kovalenko, M. V.; Scheele, M.; Talapin, D. V. Colloidal Nanocrystals with Molecular Metal Chalcogenide Surface Ligands. Science 2009, 324, 1417-1420. (22) Kovalenko, M. V.; Bodnarchuk, M. I.; Zaumseil, J.; Lee, J. S.; Talapin, D. V. Expanding the Chemical Versatility of Colloidal Nanocrystals Capped with Molecular Metal Chalcogenide Ligands. J. Am. Chem. Soc. 2010, 132, 10085-10092. (23) Zhang, H.; Jang, J.; Liu, W.; Talapin, D. V. Colloidal Nanocrystals with Inorganic Halide, Pseudohalide, and Halometallate Ligands. ACS Nano 2014, 8, 7359-7369. (24) Nag, A.; Kovalenko, M. V.; Lee, J. S.; Liu, W.; Spokoyny, B.; Talapin, D. V. Metal-Free Inorganic Ligands for Colloidal Nanocrystals: S2-, HS-, Se2-, HSe-, Te2-, HTe-, TeS32-, OH-, and NH2as Surface Ligands. J. Am. Chem. Soc. 2011, 133, 10612-10620. (25) Ban, H. W.; Park, S.; Jeong, H.; Gu da, H.; Jo, S.; Park, S. H.; Park, J.; Son, J. S. Molybdenum and Tungsten Sulfide Ligands for Versatile Functionalization of All-Inorganic Nanocrystals. J. Phys. Chem. Lett. 2016, 7, 3627-3635. (26) Jeong, H.; Yoon, S.; Kim, J. H.; Kwak, D.-H.; Gu, D. H.; Heo, S. H.; Kim, H.; Park, S.; Ban, H. W.; Park, J.; et al. Transition Metal-Based Thiometallates as Surface Ligands for Functionalization of All-Inorganic Nanocrystals. Chem. Mater. 2017, 29, 10510-10517. (27) Baek, S.; Kim, J.; Kim, H.; Park, S.; Ban, H. W.; Gu, D. H.; Jeong, H.; Kim, F.; Lee, J.; Jung, B. M.; et al. Controlled Grafting of Colloidal Nanoparticles on Graphene through Tailored Electrostatic Interaction. ACS Appl. Mater. Interfaces 2019, 11, 11824-11833. (28) Panthani, M. G.; Korgel, B. A. Nanocrystals for Electronics. Annu. Rev. Chem. Biomol. Eng. 2012, 3, 287-311. (29) Dragulescu-Andrasi, A.; Miller, L. Z.; Chen, B.; McQuade, D. T.; Shatruk, M. Facile Conversion of Red Phosphorus into Soluble Polyphosphide Anions by Reaction with Potassium Ethoxide. Angew. Chem., Int. Ed. 2016, 55, 3904-3908. (30) Tessier, M. D.; Dupont, D.; De Nolf, K.; De Roo, J.; Hens, Z. Economic and Size-Tunable Synthesis of InP/ZnE (E = S, Se) Colloidal Quantum Dots. Chem. Mater. 2015, 27, 4893-4898. (31) Zhu, W.; Michalsky, R.; Metin, O.; Lv, H.; Guo, S.; Wright, C. J.; Sun, X.; Peterson, A. A.; Sun, S. Monodisperse Au Nanoparticles for Selective Electrocatalytic Reduction of CO2 to CO. J. Am. Chem. Soc. 2013, 135, 16833-16836. (32) Liu, C.; Wu, X.; Klemmer, T.; Shukla, N.; Weller, D.; Roy, A. G.; Tanase, M.; Laughlin, D. Reduction of Sintering during Annealing of FePt Nanoparticles Coated with Iron Oxide. Chem. Mater. 2005, 17, 620-625.


Page 9 of 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(33) Weidman, M. C.; Beck, M. E.; Hoffman, R. S.; Prins, F.; Tisdale, W. A. Monodisperse, Air-Stable PbS Nanocrystals via Precursor Stoichiometry Control. ACS Nano 2014, 8, 6363-6371. (34) Park, Y. I.; Kim, H. M.; Kim, J. H.; Moon, K. C.; Yoo, B.; Lee, K. T.; Lee, N.; Choi, Y.; Park, W.; Ling, D.; et al. Theranostic Probe Based on Lanthanide-Doped Nanoparticles for Simultaneous In Vivo Dual-Modal Imaging and Photodynamic Therapy. Adv. Mater. 2012, 24, 5755-5761. (35) Winchester, R. A.; Whitby, M.; Shaffer, M. S. Synthesis of Pure Phosphorus Nanostructures. Angew. Chem., Int. Ed. 2009, 48, 3616-3621. (36) Wang, F.; Zi, W.; Zhao, B. X.; Du, H. B. Facile Solution Synthesis of Red Phosphorus Nanoparticles for Lithium Ion Battery Anodes. Nanoscale Research Letters. 2018, 13:356. (37) Liu, Y.; Hu, Z.; Yu, J. C. Liquid Bismuth Initiated Growth of Phosphorus Microbelts with Efficient Charge Polarization for Photocatalysis. Applied Catalysts B: Environmental 2019, 25, 100-106. (38) Kim, J.; Baik, S. S.; Ryu, S. H.; Sohn, Y.; Park, S.; Park, B. G.; Denlinger, J.; Yi, Y.; Choi, H. J.; Kim, K. S. Observation of Tunable Band Gap and Anisotropic Dirac Semimetal State in Black Phosphorus. Science 2015, 349, 723-726. (39) Han, C.; Hu, Z.; Gomes, L. C.; Bao, Y.; Carvalho, A.; Tan, S. J. R.; Lei, B.; Xiang, D.; Wu, J.; Qi, D.; et al. Surface Functionalization of Black Phosphorus via Potassium toward High-Performance Complementary Devices. Nano Lett. 2017, 17, 4122-4129. (40) Jang, J.; Oh, J. Y.; Kim, S. K.; Choi, Y. J.; Yoon, S. Y.; Kim, C. O. Electric-Field-Enhanced Crystallization of Amorphous Silicon. Nature 1998, 395, 481-483. (41) Moreels, I.; Lambert, K.; Smeets, D.; De Muynck, D.; Nollet, T.; Martins, J. C.; Vanhaecke, F.; Vantomme, A.; Delerue, C.; Allan, G.; et al. Size-Dependent Optical Properties of Colloidal PbS Quantum Dots. ACS Nano 2009, 3, 3023-3030. (42) Hyun, B. R.; Zhong, Y. W.; Bartnik, A. C.; Sun, L.; Abruna, H. D.; Wise, F. W.; Goodreau, J. D.; Matthews, J. R.; Leslie, T. M.; Borrelli, N. F. Electron Injection from Colloidal PbS Quantum Dots into Titanium Dioxide Nanoparticles. ACS Nano 2008, 2, 2206-2212. (43) Qi, L.; Dong, K.; Zeng, T.; Liu, J.; Fan, J.; Hu, X.; Jia, W.; Liu, E. Three-Dimensional Red Phosphorus: A Promising Photocatalyst with Excellent Adsorption and Reduction Performance. Catal. Today 2018, 314, 42-51. (44) Rath, A. K.; Bernechea, M.; Martinez, L.; Konstantatos, G. Solution-Processed Heterojunction Solar Cells Based on P-Type

(45)

(46)

(47)

(48) (49) (50)

(51)

(52)

(53)

(54)

PbS Quantum Dots and N-Type Bi2S3 Nanocrystals. Adv. Mater. 2011, 23, 3712-3717. Szendrei, K.; Cordella, F.; Kovalenko, M. V.; Böberl, M.; Hesser, G.; Yarema, M.; Jarzab, D.; Mikhnenko, O. V.; Gocalinska, A.; Saba, M.; et al. Solution-Processable Near-IR Photodetectors Based on Electron Transfer from PbS Nanocrystals to Fullerene Derivatives. Adv. Mater. 2009, 21, 683-687. Zhang, D.; Gan, L.; Cao, Y.; Wang, Q.; Qi, L.; Guo, X. Understanding Charge Transfer at PbS-Decorated Graphene Surfaces Toward A Tunable Photosensor. Adv. Mater. 2012, 24, 27152720. Kufer, D.; Nikitskiy, I.; Lasanta, T.; Navickaite, G.; Koppens, F. H.; Konstantatos, G. Hybrid 2D-0D MoS2-PbS Quantum Dot Photodetectors. Adv. Mater. 2015, 27, 176-180. Gratzel, M., Photoelectrochemical Cells. Nature, 2001, 414, 338-344. Walukiewicz, W. Intrinsic limitations to the doping of wide-gap semiconductors. Physica B, 2001, 302-303, 123-134. Rodríguez-Cantó, P. J.; Abargues, R.; Gordillo, H.; Suárez, I. Chirvony, V.; Albert, S.; Martínez-Pastor, J. UV-patternable nanocomposite containing CdSe and PbS quantum dots as miniaturized luminescent chemo-sensors. RSC Adv., 2015, 5, 1987419883. Milleville, C. C.; Pelcher, K. E.; Sfeir, M. Y.; Banerjee, S.; Watson, D. F. Directional Charge Transfer Mediated by Mid-Gap States: A Transient Absorption Spectroscopy Study of CdSe Quantum Dot/β-Pb0.33V2O5 Heterostructures. J. Phys. Chem. C 2016, 120, 5221-5232. Li, H.; Yu, H.; Quan, X.; Chen, S.; Zhao, H. Improved Photocatalytic Performance of Heterojunction by Controlling the Contact Facet: High Electron Transfer Capacity between TiO2 and the {110} Facet of BiVO4 Caused by Suitable Energy Band Alignment. Adv. Funct. Mater. 2015, 25, 3074-3080. Yang, J.; Kwak, H.; Lee, Y.; Kang, Y. S.; Cho, M. H.; Cho, J. H.; Kim, Y. H.; Jeong, S. J.; Park, S.; Lee, H. J.; Kim, H. MoS2InGaZnO Heterojunction Phototransistors with Broad Spectral Responsivity. Appl. Phys. Lett. 2016, 8, 13,8576-8582. Wu, H.; Si, H.; Zhang, Z.; Kang, Z.; Wu, P.; Zhou, L.; Zhang, S.; Zhang, Z.; Liao, Q.; Zhang, Y. All-inorganic Perovskite Quantum Dot-Monolayer MoS2 Mixed-Dimensional van der Waals Heterostructure for Ultrasensitive Photodetector. Adv. Sci. 2018, 5, 1801219.



Table of Contents


Page 10 of 10

Polyphosphide Precursor for Low-Temperature Solution-Processed

Recommend Documents