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PbSe Quantum Dots Sensitized High-Mobility Bi2O2Se Nanosheets for High-Performance and Broadband Photodetection Beyond 2 Micrometers peng luo, Fuwei Zhuge, Fakun Wang, Linyuan Lian, Kailang Liu, Jianbing Zhang, and Tianyou Zhai ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.9b03124 • Publication Date (Web): 13 Aug 2019 Downloaded from pubs.acs.org on August 13, 2019

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PbSe Quantum Dots Sensitized High-Mobility Bi2O2Se Nanosheets for High-Performance and Broadband Photodetection Beyond 2 Micrometers Peng Luo,† Fuwei Zhuge,*,† Fakun Wang,† Linyuan Lian,‡ Kailang Liu,† Jianbing Zhang,‡ Tianyou Zhai*,† †State

Key Laboratory of Material Processing and Die & Mould Technology, School of

Material Sciences and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China ‡School

of Optical and Electronic Information, Huazhong University of Science and

Technology, Wuhan, 430074, China *E-mail: [email protected] *E-mail: [email protected]

ACS Paragon Plus Environment

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ABSTRACT: As an emerging two-dimensional (2D) semiconductor, Bi2O2Se has recently attracted broad interests in optoelectronic devices for its superior mobility and ambient stability, whereas the diminished photoresponse near its inherent indirect bandgap (0.8 eV or

λ = 1550 nm) severely restricted its application in the broad infrared spectra. Here, we report the Bi2O2Se nanosheets based hybrid photodetector for short wavelength infrared (SWIR) detection up to 2 µm via PbSe colloidal quantum dots (CQDs) sensitization. The type II interfacial band offset between PbSe and Bi2O2Se not only enhanced the device responsivity compared to bare Bi2O2Se but also sped up the response time to ~4 ms, which was ~300 times faster than PbSe CQDs. It was further demonstrated that the photocurrent in such 0D-2D hybrid photodetector could be efficiently tailored from photoconductive to photogate dominated response under external field effects, thereby rendering a sensitive infrared response >103 A/W at 2 µm. The excellent performance up to 2 µm highlight the potential of field effect modulated Bi2O2Se based hybrid photodetectors in pursuing highly sensitive and broadband photodetection.

KEYWORDS: Bi2O2Se, 0D-2D heterostructure, infrared photodetection, gate modulation, PbSe


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Atomically thin 2D semiconductors are attracting enormous attention based on their 2D confined structure and tunable properties via layer number,1,2 phase,3,4 or field effect engineering,5-7 for what great potential was expected for them as the building blocks in electronics and optoelectronics devices.8-11 In addition to the rapidly growing 2D materials,

e.g. graphene, transition metal dichalcogenides (TMDs), black phosphorous (BP), Bi2O2Se recently arises as a new 2D semiconductor with excellent carrier mobility (~450 cm2/Vs at room temperature) and ambient stability.12,13 Recently, numerous efforts have been devoted to tailor the inherent material properties in transistor, memristor, and photodetector by optimizing the synthesis, etch and transfer processes.14-19 However, in photodetectors, the photoresponse performance of Bi2O2Se near its bandgap decreased dramatically to 105 A/W) and detectivity (1015 Jones) within the visible spectrum.21 In view of the numerous infrared oriented applications (e.g., telecommunication, night vision, medical imaging, etc.),22-24 it is therefore of general interests to extend the photoresponse spectra of Bi2O2Se to the broad infrared range. With their high extinction coefficient and size tunable bandgap, colloidal quantum dots (CQDs) of narrow bandgap semiconductors (PbS, PbSe, HgTe, HgSe, etc.) have been coupled to 2D materials for the engineering of response spectra in detectors.25-29 High sensitivity (>107 A/W) have been achived via the photogating effect based on the charge separation at the


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heterointerface between CQDs and 2D materials.26 As the semiconductor channel, 2D Bi2O2Se could potentially offers a high mobility charge transport pathway when integrated with CQDs. An essential factor that determines the overall device performance was the interfacial band alignment that governs the charge separation across the heterointerface.30,31 Though graphene exhibits superior mobility over others, its zero bandgap characteristics make it accept both electrons and holes simultaneously from CQDs, therefore leading to poor charge separation efficiency.27,32,33 However, when choosing semiconductor channels for a hybrid 0D-2D detector, an elusive task arises for setting up proper interfacial band alignment with the narrow bandgap CQDs, which depends not only on the electron affinity, bandgap but also the work function of each component.29,34,35 Considering the ultrathin nature of 2D semiconductors, it is reasonable to believe external field effects could be potentially exploited to tune the charge transfer at 0D-2D hybrid interface, as the case found in multilayer van der Waals (vdW) heterostructures.36-39 The synergetic tailoring of the photoresponse behavior of 0D-2D hybrid photodetectors for ultrasensitive gain mechanism while extending the photoresponse spectra to infrared shall be viable on such playground, which is yet to be demonstrated. In this report, we explore field effect tuned infrared photodetection based on 2D Bi2O2Se coupled with PbSe CQDs. Ultrasensitive infrared response beyond 2 μm via 2D Bi2O2Se was demonstrated based on the type II interface formed with PbSe CQDs, which rendered charge injection from PbSe CQDs to Bi2O2Se upon illumination. With the fast charge transfer dynamics at the established type II interface, the photoresponse speed (103 A/W at 2 μm. Exploring field-effect tuned gain mechanism in such hybrid photodetectors is therefore believed to potentially deliver high performance detection in the broadband infrared spectra.


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RESULTS AND DISCUSSION Ternary Bi2O2Se has a layered structure in which planar covalently bonded [Bi2O2]n2n+ layers and separate [Se]n2n- layers stack alternately in a tetragonal unit cell (I4/mmm, a = b = 3.88 Å,

c = 12.16 Å and Z = 2),12,18 as illustrated in Figure 1a. Monolayer Bi2O2Se exhibits the thickness ~0.61 nm. The strong electrostatic effect between [Bi2O2]n2n+ and [Se]n2n- preferentially lead to vertical growth of Bi2O2Se compared to most other 2D semiconductors coupled with weak van der Waals interaction. Therefore, to achieve thin Bi2O2Se nanosheets by chemical vapor deposition (CVD), freshly cleaved fluorophlogopite mica [KMg3(AlSi3O10)F2] with similarly structure ([Mg3(AlSi3O10)F2]- and K+ layers stacked alternately) was chosen as the substrate to promote lateral 2D growth.14,16,18 In a typical growth, the substrates were put at the downstream in a quartz tube, while Bi2Se3 and Bi2O3 powder were put at the high temperature zone for the generation of vapor sources by sublimation, as illustrated in Figure 1b. Large-area single crystal Bi2O2Se nanosheets with lateral size up to 50 m and thickness around ~8 nm (Figure 1c, d) were successfully synthesized in this way. The high-resolution transmission electron microscope (HRTEM) image shown in Figure 1e and the inset selected area electron diffraction (SAED) pattern both agreed well with the c-axis oriented tetragonal crystal of Bi2O2Se. It is noted that the as-prepared Bi2O2Se was slightly Se deficient with a Bi:O:Se ratio of 2:2.1:0.9, as indicated by the energy dispersive X-ray spectra shown in supplementary information Figure S1a. The Se vacancy was believed to contribute to the heavily n-type doped behavior of Bi2O2Se,40 which could be compensated by using Se as the direct sublimation vapor


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source.17 The as-fabricated Bi2O2Se was then transferred to SiO2/Si substrate by using HF etching and polymethyl methacrylate (PMMA) assisted handling processes for further device fabrication. The successfully transferred nanosheet of Bi2O2Se on SiO2/Si substrate was examined by the scanning electron microscopy (SEM) and Raman. Its uniformity was confirmed by elemental mapping and Raman mapping at 159 cm-1 (supplementary information Figure S1b and S1c). Later, electrical contacts to Bi2O2Se were made by using standard photolithography process and Cr/Au (5/80 nm) electrodes (deposited by electron beam evaporation). All samples displayed Ohmic contact with linear I-V characteristics, which under back Si-gate modulation can be significantly modulated (Figure 1f). A typical example of measured transfer curve was displayed in Figure S1d at Vds = 1 V. The mobility (μe) and carrier concentration (n) was then extracted as:41

𝜇e =

∆𝐼ds ∆𝑉gs

∙

𝐿 , 𝑊𝐶ox𝑉ds

𝑛=

𝜎 𝑒∙𝜇

(1)

where L and W are the length and width of source-drain channel, Cox is the capacitance of 11.5 nF/cm2 for 300 nm SiO2 layer and 𝜎 is the conductivity of Bi2O2Se. Based on transconductance measurements on more than 20 samples, the maximum mobility and carrier concentration of Bi2O2Se under gate modulation were estimated to be ~20-550 cm2/Vs and 1018-1019 cm-3 (Figure 1g), which was considerably higher than other CVD grown transition metal dichalcogenides (MoS2, WSe2, etc.) without deliberate optimization.10,42-44


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With an indirect bandgap of ~0.8 eV,12,13,45 a disadvantage of Bi2O2Se was that it exhibit inherent photoresponse up to ~1500 nm with rapidly diminished extinction coefficient near the band edge, which limited the device responsivity.16,20 As shown in the Figure 1h, the absorption of Bi2O2Se nanosheets at 2-12 nm thickness decreased dramatically >1000 nm due to its indirect band. Integration with additional sensitizers with high extinction coefficient is however possible to construct an efficient broadband photodetector by taking advantage of its high mobility. Here, on the as-prepared Bi2O2Se transistor, we further prepared sensitizing PbSe CQDs with characteristic diameter d ~6.5 nm (as revealed in the TEM image in Figure 2a) and a narrow bandgap of 0.6 eV that may enable photodetection spectrum beyond 2 µm. In Figure 2b, the obtained CQDs solution absorption exhibited a first exciton absorption ~2100 nm, and the film ~2130 nm with slightly redshift. The results matched well with the predicted energy bandgap following the relation: Eg = 0.278 + (0.016 d2 + 0.209 d + 0.45)-1.46 By using a facile spin coating process illustrated in Figure 2c, the PbSe CQDs were assembled directly on Bi2O2Se. After each spin-coating, the CQDs were ligand-exchanged by using drop-casted EDT solution. The sample was then annealed at 95 ℃ for 20 min to improve neck connection and therefore carrier mobility within CQDs. From X-ray diffraction (XRD) pattern, TEM image, EDS mapping shown in Figure 2d-g, the successful hybrid combination of PbSe CQDs on Bi2O2Se nanosheet was confirmed. The thickness of PbSe CQDs layer was ~20-25 nm after 2 repeated spin-coating cycles (Figure S2a and S2b). Based on the results in high-angle annular dark field scanning TEM (HAADF-STEM) and the fine surface morphology under AFM (Figure S2c and S2d), the CQDs were expected almost closely packed with some top surface


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vacancies by such spin-coating process, which may be important to ensure the charge transfer pathway. The interfacial energy band alignment between PbSe CQDs and Bi2O2Se essentially determines the resulted charge transfer under illumination. In order to gain information on the energy band alignment when PbSe CQDs and Bi2O2Se were brought into contact, ultraviolet photoelectron spectra (UPS) measurements were conducted. In Figure 3a, the obtained valance band spectra and second electron cutoff energy (Ecut) of Bi2O2Se and PbSe CQDs were displayed. The work function (W) of PbSe and Bi2O2Se were estimated to be respectively 4.07 and 4.37 eV, according to W = hν - Ecut, where hν = 21.21 eV is the photon energy of He I light source. This result was confirmed by the measured contact potential difference (CPD = 282 meV) between PbSe CQDs and Bi2O2Se in kelvin-probe force microscopy (KPFM), as shown in Figure S3. On the other hand, the valence band maximum (VBM) of the bare PbSe and Bi2O2Se were determined to be respectively 0.28 eV and 0.58 eV below their Fermi level (EF). Therefore, a type II band diagram in Figure 3b was suggested based on the bandgap of PbSe (0.6 eV) and Bi2O2Se (0.8 eV), and the above estimated work function and valance band position. However, since PbSe CQDs exhibited lower work function, electrons would be transferred to Bi2O2Se when they are brought in contact. The charge transfer then formed interfacial dipoles which impeded further electron injection into Bi2O2Se, as indicated in Figure 3b. However, with the large conduction band offset ~0.4 eV, electron injection into Bi2O2Se was still favorable under excitation. Engineering the strength


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of such charge transfer dipole played vital role in optimizing the photodetection performance, as will be discussed later. Next, we examine the photodetection performance of the hybrid photodetector aiming for SWIR detection. As indicated in Figure 4a, the device was first configured into side-to-side connected Bi2O2Se transistor and blank electrodes, so that control PbSe detector was obtained simultaneously with PbSe sensitized Bi2O2Se transistor after spin-coating, thus avoiding potential inhomogeneity issues in PbSe CQDs thin film. An optical image of the device was shown in the inset. The thickness of covered Bi2O2Se channel was ~6.2 nm (~10 layers), the width and length of the device were 3.9 μm and 1.5 μm respectively. As indicated in Figure 4b, introducing PbSe CQDs onto Bi2O2Se was found to increase the channel current by ~10 times in dark due to the earlier mentioned electron transfer from PbSe to Bi2O2Se, despite PbSe CQDs displayed p-type behavior (Figure S4). Under 532 nm excitation (3.7 mW/cm2), the photocurrent (388.7 nA, Iph or ΔI = Ilight – Idark) in hybrid photodetector doubled that of bare Bi2O2Se (190.0 nA), and was ~300 times higher than PbSe CQDs (1.2 nA). Such obvious photocurrent enhancement was attributed to charge transfer between PbSe and Bi2O2Se, and the superior mobility in Bi2O2Se (~58.9 cm2/Vs) compared to PbSe CQDs (~0.018 cm2/Vs). This was because the increase of photoconductive gain in detector by the reduce of carrier transit time (τtransit) in channel, which was related with the channel length (L), voltage bias (V) and carrier mobility (μ) as τtransit = L2/μV.47 Figure 4c shows the photoresponse spectra of compared devices. It should be noted that due to the light intensity dependence of photoresponse and


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wavelength dependent light intensity from broad band light sources (Figure S5), the response spectra were used to only compare the performance of different detectors at the same wavelength. When compared to the initial Bi2O2Se, the hybrid photodetector exhibited 2-5 times improved responsivity below 1000 nm due to the enhanced light absorption ability by introducing PbSe CQDs. Increasing the thickness of Bi2O2Se layer reduced the enhancement factor in such spectra range (Figure S6), while the thickness of PbSe layer was found optimal by 2 spin-coating cycles (Figure S7), due to likely the balance between effective charge transfer distance and light absorption in PbSe CQDs. Beyond the absorption edge of Bi2O2Se, the enhancement in hybrid photodetector became more apparent. At λ>1500 nm, the responsivity (R = Iph/PS, where P is the light power intensity, S is the effective photodetection area)48 of bare Bi2O2Se diminished dramatically, while PbSe/Bi2O2Se hybrid photodetector exhibited apparent photoresponse with R >100 A/W. In Figure 4d, the power dependence of device responsivity under 1456 nm and 2000 nm infrared illumination were compared to that of bare PbSe CQDs. A typical transient photoresponse of the hybrid detector at 2000 nm was displayed in Figure 4e. It was found that the device responsivity in PbSe and hybrid photodetector decreased with illumination intensity, which fitted to characteristics of photogating effect dominated detection.49,50 However, the underlying photogate mechanism for the hybrid photodetector was different from that of bare Bi2O2Se or PbSe CQDs. In the case of bare Bi2O2Se or PbSe CQDs, the photogating effect originated from minority carrier trapping at defect states, while in the


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hybrid photodetector, this was expected to stem from charge separation at the type II interface.50 The speculation was based on the fact that different photoresponse dynamics were observed in the several detectors operating at 532 nm and 2000 nm, as indicated in Figure 4f and Figure S8. The photoresponse decays (the time photoresponse decreased from its 90% to 10%) for hybrid photodetector were respectively 1.5 s and 4 ms at 532 and 2000 nm. In comparison, the values were respectively 1.8 s and 1.5 s for bare Bi2O2Se and PbSe CQDs. It was noticed that the hybrid photodetector exhibited distinct response dynamics at different excitation wavelengths. At 532 nm, the hybrid photodetector exhibited similar response dynamic as that of bare Bi2O2Se, while at longer wavelengths beyond the absorption band edge of Bi2O2Se, the device displayed much faster response behavior than that of PbSe CQDs, though the latter solely contributed to the optical absorption. The fast response speed at long wavelengths was ascribed to the photovoltaic separation of photo-generated electron-hole pairs at the type II interface, which we confirmed by directly measuring the self-driven photoresponse across the Bi2O2Se/PbSe heterojunction (Figure S9). However, a question arises when considering the same charge separation induced photogating was not applicable at shorter wavelength excitations. In Figure 4g, we proposed that this is related to the nonradiative energy transfer (NRET)51,52 from PbSe CQDs to Bi2O2Se via Förster resonance energy transfer, a process that had been observed in other hybrid systems of 0D CQDs and 2D materials.53 At shorter wavelengths that lies within the absorption band edge of Bi2O2Se (Ehν>Eg,semi in Figure 4g), the exciton in PbSe CQDs was transferred to Bi2O2Se via


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NRET processes by the dipole-dipole interaction. And electron-hole pairs could then be generated in Bi2O2Se. In Figure S10a, the overlapped emission spectrum of PbSe CQDs and the absorption spectrum of Bi2O2Se were displayed, which is a prerequisite of such NRET processes. An evidence of the NRET process was that when putting PbSe CQDs on Bi2O2Se, the photoluminescence lifetime of excitons in PbSe was quenched by a factor of ~1.5 (Figure S10b), which shall be driven by the different exciton lifetime between PbSe (τA) and Bi2O2Se (τB). The results corresponded to a NRET efficiency of ~30%. Though not significant, the value was expected enough to excite electron-hole pairs in Bi2O2Se. The photoresponse dynamics in hybrid detector then displayed similar behavior as Bi2O2Se, which was limited by the time constant of minority carrier trapping/emission in defects (denoted by τtr and τem in Figure 4g) rather than the photovoltaic charge separation at interface, as illustrated in Figure 4g(i).50,54 Since the efficiency of such NRET process depends on the overlapped exciton emission spectra in CQDs and absorption spectra in Bi2O2Se, the photoresponse in hybrid photodetector beyond the absorption edge of Bi2O2Se switched into a fast response dynamic by photovoltaic effects,

e.g. under the illumination at 1456 nm (Figure S11) and 2000 nm (Figure 4f). With the type II band offset between PbSe CQDs and Bi2O2Se, holes were separated to PbSe CQDs while electrons were injected into Bi2O2Se. Though the separated carriers could still be trapped in defect states in PbSe or Bi2O2Se, they did not significantly degrade the photoresponse dynamics. This was because in bare PbSe and Bi2O2Se the response dynamics were limited by minority carrier trapping in deep levels, while in present type II heterostructure, electrons and holes after separation were trapped and emitted as majority carriers with considerably lower trap


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energy,50 as illustrated in the energy diagrams in Figure 4g(ii), therefore enabling the observed fast response behavior. The photovoltaic separation of photo-generated electron-hole pairs at the type II interface of PbSe CQDs/Bi2O2Se determined the photogating effect and was essential for the desired fast and high gain photodetection. However, due to the early-mentioned charge transfer dipole at the interface, the charge separation could be partially hampered, thus limiting the observed photoresponse. Here, we demonstrated the degree of photogating effect in the overall photocurrent could be tuned by exploiting external gate modulation. As illustrated in Figure 5a, back Si substrate was used as the gate terminal to modulate the Bi2O2Se channel. Figure 5b shows the transfer curve of a hybrid PbSe/Bi2O2Se photodetector under dark and varied light excitation intensity at 2000 nm under Vds =1 V. Unlike bare Bi2O2Se that exhibited a high onoff ratio ~105 (Figure S12), the current in hybrid photodetector could not be completely turned off under a large negative gate bias Vg = -100 V. This was attributed to the pinning of fermi level in channel to the valance band of PbSe CQDs under large negative gate bias due to the electron transfer from PbSe to Bi2O2Se. Thus, the hybrid transistor maintained linear Ohmic contact under all back-gate modulation conditions (Figure S12). To investigate the photogating contribution to the overall photocurrent, in Figure 5c we extracted the gate modulated photocurrent under varied excitation intensity. The light intensity dependence was fitted using Iph  Pα, where 0≤α≤1 could depict the photocurrent generation mechanisms in detector classified as (i) photoconductive with α = 1 and (ii) photogating dominated for α = 0.55,56 It was


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found that α changed from ~0.98 to 0.12 under varied gate modulation from -50 to 50 V (Figure 5d), indicating the dramatically modulated photoresponse behavior in the hybrid photodetector under field effect. Though similar tuning of the photogating effect in detectors has been recently discussed by considering the gate modulated trap-filling characteristics in ultrathin 2D materials, the phenomenon was rarely investigated or discussed in heterostructure detectors. Here, we attributed the widely tuned photocurrent generation mechanism to the modulated interfacial charge transfer dipole between PbSe CQDs and Bi2O2Se. As schematically illustrated in Figure 5e, the interfacial dipole at Vg = 0 V stemmed from the initial electron injection from PbSe to Bi2O2Se because of their work function difference. The formation of such dipole impeded further charge separation of photogenerated electrons and holes, and therefore was prone to suppress the photogate response in detector. When considering the direction of electric field (E) by gate bias compared to the interfacial dipole, the strength of the dipole can be respectively increased or decreased at negative (Vg0). As a result, the charge separation efficiency at the interface could be modulated, thereby influenced the photogating effect in detectors. With the dramatically modulated photocurrent generation in detector, an optimization of the device sensitivity is then possible. In Figure 6a, the device responsivity at 2000 nm was extracted under varied gate bias. Notably, at Vg = 100 V, the photocurrent became dominated by photogating effect, yield the most sensitive detection with R ~3  103 A/W at 35 mW/cm2. This was ascribed to the promoted charge separation at the type II interface given that positive


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gate bias tended to neutralize the interface charge transfer dipole. As indicated in Figure 6b, compared to bare Bi2O2Se or PbSe detectors, the present PbSe/Bi2O2Se hybrid detector exhibited the extended infrared detection up to 2 μm and dramatically enhanced responsivity while offering a fast response speed less than 4 ms. When compared to previous 2D photodetectors based on graphene,57-59 black phosphorous,60-62 Bi2O2Se,16,20 and typical 0D-2D hybrid photodetectors,26,28,33,63-68 the present PbSe CQDs sensitized Bi2O2Se provided a competitive performance at the extended SWIR band up to 2 μm. As indicated in Figure S13, further optimization of the responsivity was likely attainable given larger source-drain bias that reduced the carrier transit time in channel. These results therefore demonstrated the valuable potential in exploring interfacial band alignment in type II heterostructures and gate modulation strategies for optimized photodetection.


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CONCLUSION In summary, we have demonstrated a broadband and high performance infrared photodetector based on the hybrid combination of high mobility 2D Bi2O2Se and infrared sensitive PbSe CQDs. Fast photoresponse 103 A/W and fast response characteristic. The finding here to optimize hybrid photodetectors based on field effect tuned interfacial band alignment was thus expected to leverage further efforts in searching superior photodetectors in the broad infrared spectra.


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METHODS Synthesis of Bi2O2Se thin Nanosheets. The few layers Bi2O2Se nanosheets were grown by CVD process in a quartz tube (length 30 cm, diameter 3 cm). The Bi2O3 powder (Alfa Aesar, 99.999%) and Bi2Se3 power (Alfa Aesar, 99.999%) were respectively put at the tube hot center and its 8 cm upstream. Freshly peeled mica substrates were placed in the downstream by 12 ~14 cm. The quartz tube was evacuated firstly and flushed with high-purity Ar (99.99%) for several times to avoid ambient contamination. The furnace was then heated with a ramping rate of 2-5 ℃/min, kept at 700-750 ℃ for 25 min, and cooled down naturally to room temperature. During the growth, 200 sccm Ar gas flow was used to carry the reactive vapor source from upstream to the low temperature zone where substrate were located. Synthesis of PbSe CQDs. Colloidal PbSe QDs with the first excitation absorption peak around 2100 nm were synthesized by modified Zhang’s method:69 OLA (36 mL) and 9 mmol of PbCl2 were degassed under vacuum at 80 °C and heated to 140 °C maintained for 30 min under nitrogen, then the suspension was allowed to cool to 30 °C, 110 μL of 1M DPPSe diluted in 2 mL of ODE, 0.57 mL of 1M TOPSe and 110 μL of DPP were injected sequentially to the lead precursor solution at 30 °C. Next, the reaction solution was reheated to 160 °C maintained for 15 min, then 0.57 mL of 1 M TOPSe and 110 μL of DPP diluted in 2 mL of ODE were injected sequentially to the reaction solution, and the solution was maintained at 160 °C for 15 min. And then the reaction was quenched by a water bath, and 20 mL of hexane and 20 mL of OA were added at 70 and 40 °C, respectively, followed by vigorous stirring for 10 min. The raw


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solution was centrifugation after the addition of hexane and OA, and the supernatant was discarded. The precipitate was dispersed in tetrachloroethylene solvent, the unreacted lead precursors were precipitated from the solvent by centrifugation and the precipitate was discarded. The supernatant solution was collected and precipitated by adding acetone. After centrifugation, the supernatant was discarded and the precipitated PbSe QDs was collected. Characterization. To evaluate the prepared Bi2O2Se nanosheets, PbSe QDs and the hybrid PbSe/Bi2O2Se heterostructure, atomic force microscope (Dimension Icon, Bruker), transmission electron microscope (Technai G2 F30, FEI), spectrophotometer (UV-3600, Shimadzu), micro-zone UV-Vis-IR absorption spectroscopy (Metatest, MStarter ABS), confocal Raman system (Alpha 300R, WITec), X-ray diffraction (PANalytical X’pert PRODY2198 with Cu-Kα radiation) were used. To peel off the Bi2O2Se thin nanosheet for TEM study, a wet chemical etching method was used based on polymethyl methacrylate (PMMA) and dilute HF solution (2%), the PMMA was then removed under heated acetone vapor. To gain the information on energy band alignment between PbSe CQDs and Bi2O2Se, ultraviolet photoelectron spectra (Axis Ultra DLD, Kratos) and kelvin probe force microscopy (Dimension Icon, Bruker) were measured. Device Fabrication and Measurements. The Bi2O2Se and hybrid Bi2O2Se/PbSe photodetector were fabricated using standard electron beam lithography processes, with the contact electrodes made from Cr/Au (5/80 nm) using thermal evaporation method. To obtain PbSe sensitization, bare Bi2O2Se device was spin-coated with PbSe CQDs. In detail, 30 mg/mL


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octane PbSe QDs solution was coated on the whole substrate at 2500 rpm for 30 s. 1 mmol/L EDT/acetonitrile solution was then drop casted for ligand exchange and dried after 30 s. The process was repeated twice and the sample was finally annealed at 90 ℃ for 10 min. After EDT exchange, the hybrid device displayed consistent photodetection performance over several days (Figure S14), suggesting the good ambient stability of the processed CQDs. All electrical and photodetection results were tested in a probe station (TTPX, Lakeshore) with semiconductor analyzer (B1500A, Agilent). Collimated laser sources (532 nm, 1456 nm and 2000 nm) were then used to shine light on the device, with the power calibrated using powermeter (FieldMaxII-TO, Coherent). ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: EDX spectra and SEM image of Bi2O2Se, typical transfer curve of Bi2O2Se device, OM image and AFM image of spin-coated PbSe quantum dots on SiO2 substrate, AFM image and KPFM characterization of bare PbSe and Bi2O2Se on SiO2 substrate, intensity spectra of adopted light sources used in measuring response spectra, optimal Bi2O2Se and PbSe thickness for the hybrid photodetector, transient response dynamics of PbSe and Bi2O2Se/PbSe hybrid infrared phototransistor under 1456 nm and 2000 nm excitation, self-driven photovoltaic response to


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2000 nm excitation by the Bi2O2Se/PbSe heterojunction, spectra overlap and quenched PL lifetime for NRET processes, transfer curves and back-gate modulated photocurrent of Bi2O2Se, PbSe and hybrid device under dark and 2000 nm excitation, voltage bias- and light intensitydependent photocurrent in Bi2O2Se/PbSe hybrid photodetector under 2000 nm excitation, and the ambient stability of hybrid detectors lasting for days. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] *E-mail: [email protected] ORCID Tianyou Zhai: 0000-0003-0985-4806 ACKNOWLEDGMENT This work was supported by the National Nature Science Foundation of China (21825103, 61804059 and 51727809), National Basic Research Program of China (2015CB932600), and National Key Research and Development Program of “Strategic Advanced Electronic Materials” (2016YFB0401100). The authors thank the Analytical and Testing Centre of Huazhong University of Science and Technology.


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REFERENCES (1)

Xi, X.; Zhao, L.; Wang, Z.; Berger, H.; Forro, L.; Shan, J.; Mak, K. F. Strongly Enhanced

Charge-Density-Wave Order in Monolayer NbSe2. Nat. Nanotechnol. 2015, 10, 765-769. (2)

Li, X. L.; Han, W. P.; Wu, J. B.; Qiao, X. F.; Zhang, J.; Tan, P. H. Layer-Number

Dependent Optical Properties of 2D Materials and Their Application for Thickness Determination. Adv. Funct. Mater. 2017, 27, 1604468. (3)

Keum, D. H.; Cho, S.; Kim, J. H.; Choe, D. H.; Sung, H. J.; Kan, M.; Kang, H.; Hwang, J.

Y.; Kim, S. W.; Yang, H.; Chang, K. J.; Lee, Y. H. Bandgap Opening in Few-Layered Monoclinic MoTe2. Nat. Phys. 2015, 11, 482-486. (4)

Wang, Y.; Xiao, J.; Zhu, H.; Li, Y.; Alsaid, Y.; Fong, K. Y.; Zhou, Y.; Wang, S.; Shi, W.;

Wang, Y.; Zettl, A.; Reed, E. J.; Zhang, X. Structural Phase Transition in Monolayer MoTe2 Driven by Electrostatic Doping. Nature 2017, 550, 487-491. (5)

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. (6)

Baugher, B. W.; Churchill, H. O.; Yang, Y.; Jarillo-Herrero, P. Optoelectronic Devices

Based on Electrically Tunable p-n Diodes in a Monolayer Dichalcogenide. Nat. Nanotechnol. 2014, 9, 262-267. (7)

Wang, R. Y.; Zhou, F. Y.; Lv, L.; Zhou, S. S.; Yu, Y. W.; Zhuge, F. W.; Li, H. Q.; Gan,

L.; Zhai, T. Y. Modulation of the Anisotropic Electronic Properties in ReS2 via Ferroelectronic Film. CCS Chem. 2019, 1, 268-277. (8)

Tan, C.; Cao, X.; Wu, X. J.; He, Q.; Yang, J.; Zhang, X.; Chen, J.; Zhao, W.; Han, S.; Nam,

G. H.; Sindoro, M.; Zhang, H. Recent Advances in Ultrathin Two-Dimensional Nanomaterials. Chem. Rev. 2017, 117, 6225-6331.


22

Page 23 of 40 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

ACS Nano

(9)

Ajayan, P.; Kim, P.; Banerjee, K. Two-Dimensional van der Waals Materials. Phys. Today

2016, 69, 39-44. (10) Wang, Q. H.; Kalantar-Zadeh, K.; Kis, A.; Coleman, J. N.; Strano, M. S. Electronics and Optoelectronics of Two-Dimensional Transition Metal Dichalcogenides. Nat. Nanotechnol. 2012, 7, 699-712. (11) Li, L.; Han, W.; Pi, L.; Niu, P.; Han, J.; Wang, C.; Su, B.; Li, H.; Xiong, J.; Bando, Y.; Zhai, T. Emerging in‐plane Anisotropic Two‐Dimensional Materials. InfoMat 2019, 1, 54-73. (12) Wu, J.; Yuan, H.; Meng, M.; Chen, C.; Sun, Y.; Chen, Z.; Dang, W.; Tan, C.; Liu, Y.; Yin, J.; Zhou, Y.; Huang, S.; Xu, H. Q.; Cui, Y.; Hwang, H. Y.; Liu, Z.; Chen, Y.; Yan, B.; Peng, H. High Electron Mobility and Quantum Oscillations in Non-Encapsulated Ultrathin Semiconducting Bi2O2Se. Nat. Nanotechnol. 2017, 12, 530-534. (13) Chen, C.; Wang, M.; Wu, J.; Fu, H.; Yang, H.; Tian, Z.; Tu, T.; Peng, H.; Sun, Y.; Xu, X.; Jiang, J.; Schroter, N. B. M.; Li, Y.; Pei, D.; Liu, S.; Ekahana, S. A.; Yuan, H.; Xue, J.; Li, G.; Jia, J.; et al. Electronic Structures and Unusually Robust Bandgap in an Ultrahigh-Mobility Layered Oxide Semiconductor, Bi2O2Se. Sci. Adv. 2018, 4, eaat8355. (14) Fu, Q.; Zhu, C.; Zhao, X.; Wang, X.; Chaturvedi, A.; Zhu, C.; Wang, X.; Zeng, Q.; Zhou, J.; Liu, F.; Tay, B. K.; Zhang, H.; Pennycook, S. J.; Liu, Z. Ultrasensitive 2D Bi2O2Se Phototransistors on Silicon Substrates. Adv. Mater. 2019, 31, 1804945. (15) Zhang, Z.; Li, T.; Wu, Y.; Jia, Y.; Tan, C.; Xu, X.; Wang, G.; Lv, J.; Zhang, W.; He, Y.; Pei, J.; Ma, C.; Li, G.; Xu, H.; Shi, L.; Peng, H.; Li, H. Truly Concomitant and Independently Expressed Short- and Long-Term Plasticity in a Bi2O2Se-Based Three-Terminal Memristor. Adv. Mater. 2019, 31, 1805769.


23

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Page 24 of 40

(16) Li, J.; Wang, Z. X.; Wen, Y.; Chu, J. W.; Yin, L.; Cheng, R. Q.; Lei, L.; He, P.; Jiang, C.; Feng, L. P.; He, J. High-Performance Near-Infrared Photodetector Based on Ultrathin Bi2O2Se Nanosheets. Adv. Funct. Mater. 2018, 28, 1706437. (17) Wu, J.; Qiu, C.; Fu, H.; Chen, S.; Zhang, C.; Dou, Z.; Tan, C.; Tu, T.; Li, T.; Zhang, Y.; Zhang, Z.; Peng, L. M.; Gao, P.; Yan, B.; Peng, H. Low Residual Carrier Concentration and High Mobility in 2D Semiconducting Bi2O2Se. Nano Lett. 2019, 19, 197-202. (18) Wu, J.; Tan, C.; Tan, Z.; Liu, Y.; Yin, J.; Dang, W.; Wang, M.; Peng, H. Controlled Synthesis of High-Mobility Atomically Thin Bismuth Oxyselenide Crystals. Nano Lett. 2017, 17, 3021-3026. (19) Tan, C.; Tang, M.; Wu, J.; Liu, Y.; Li, T.; Liang, Y.; Deng, B.; Tan, Z.; Tu, T.; Zhang, Y.; Liu, C.; Chen, J. H.; Wang, Y.; Peng, H. Wafer-Scale Growth of Single-Crystal 2D Semiconductor on Perovskite Oxides for High-Performance Transistors. Nano Lett. 2019, 19, 2148-2153. (20) Yin, J.; Tan, Z.; Hong, H.; Wu, J.; Yuan, H.; Liu, Y.; Chen, C.; Tan, C.; Yao, F.; Li, T.; Chen, Y.; Liu, Z.; Liu, K.; Peng, H. Ultrafast and Highly Sensitive Infrared Photodetectors Based on Two-Dimensional Oxyselenide Crystals. Nat. Commun. 2018, 9, 3311. (21) Khan, U.; Luo, Y.; Tang, L.; Teng, C.; Liu, J.; Liu, B.; Cheng, H. M. Controlled VaporSolid Deposition of Millimeter-Size Single Crystal 2D Bi2O2Se for High-Performance Phototransistors. Adv. Funct. Mater. 2019, 29, 1807979. (22) Rauch, T.; Boberl, M.; Tedde, S. F.; Furst, J.; Kovalenko, M. V.; Hesser, G. N.; Lemmer, U.; Heiss, W.; Hayden, O. Near-Infrared Imaging with Quantum-Dot-Sensitized Organic Photodiodes. Nat. Photonics 2009, 3, 332-336. (23) Mueller, T.; Xia, F. N. A.; Avouris, P. Graphene Photodetectors for High-Speed Optical Communications. Nat. Photonics 2010, 4, 297-301.


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Page 25 of 40 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

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(24) Hong, G. S.; Antaris, A. L.; Dai, H. J. Near-Infrared Fluorophores for Biomedical Imaging. Nat. Biomed. Eng. 2017, 1, 0010. (25) Hetsch, F.; Zhao, N.; Kershaw, S. V.; Rogach, A. L. Quantum Dot Field Effect Transistors. Mater. Today 2013, 16, 312-325. (26) Konstantatos, G.; Badioli, M.; Gaudreau, L.; Osmond, J.; Bernechea, M.; Garcia de Arquer, F. P.; Gatti, F.; Koppens, F. H. Hybrid Graphene-Quantum Dot Phototransistors With Ultrahigh Gain. Nat. Nanotechnol. 2012, 7, 363-368. (27) 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. (28) Hu, C.; Dong, D. D.; Yang, X. K.; Qiao, K. K.; Yang, D.; Deng, H.; Yuan, S. J.; Khan, J.; Lan, Y.; Song, H. S.; Tang, J. Synergistic Effect of Hybrid PbS Quantum Dots/2D-WSe2 toward High Performance and Broadband Phototransistors. Adv. Funct. Mater. 2017, 27, 1603605. (29) Huo, N.; Gupta, S.; Konstantatos, G. MoS2-HgTe Quantum Dot Hybrid Photodetectors Beyond 2 Microm. Adv. Mater. 2017, 29, 1606576. (30) Wu, H. L.; Kang, Z.; Zhang, Z. H.; Zhang, Z.; Si, H. N.; Liao, Q. L.; Zhang, S. C.; Wu, J.; Zhang, X. K.; Zhang, Y. Interfacial Charge Behavior Modulation in Perovskite Quantum DotMonolayer MoS2 0D-2D Mixed-Dimensional van der Waals Heterostructures. Adv. Funct. Mater. 2018, 28, 1802015. (31) 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.


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Page 26 of 40

(32) Sun, Z.; Liu, Z.; Li, J.; Tai, G. A.; Lau, S. P.; Yan, F. Infrared Photodetectors Based on CVD-Grown Graphene and PbS Quantum Dots with Ultrahigh Responsivity. Adv. Mater. 2012, 24, 5878-5883. (33) Lee, Y.; Kwon, J.; Hwang, E.; Ra, C. H.; Yoo, W. J.; Ahn, J. H.; Park, J. H.; Cho, J. H. High-Performance Perovskite-Graphene Hybrid Photodetector. Adv. Mater. 2015, 27, 41-46. (34) Guo, S. R.; Bao, D. D.; Upadhyayula, S.; Wang, W.; Guvenc, A. B.; Kyle, J. R.; Hosseinibay, H.; Bozhilov, K. N.; Vullev, V. I.; Ozkan, C. S.; Ozkan, M. Photoinduced Electron Transfer Between Pyridine Coated Cadmium Selenide Quantum Dots and Single Sheet Graphene. Adv. Funct. Mater. 2013, 23, 5199-5211. (35) Haider, G.; Roy, P.; Chiang, C. W.; Tan, W. C.; Liou, Y. R.; Chang, H. T.; Liang, C. T.; Shih, W. H.; Chen, Y. F. Electrical-Polarization-Induced Ultrahigh Responsivity Photodetectors Based on Graphene and Graphene Quantum Dots. Adv. Funct. Mater. 2016, 26, 620-628. (36) Huang, M.; Li, S.; Zhang, Z.; Xiong, X.; Li, X.; Wu, Y. Multifunctional High-Performance van der Waals Heterostructures. Nat. Nanotechnol. 2017, 12, 1148-1154. (37) Zhou, X.; Hu, X.; Zhou, S.; Song, H.; Zhang, Q.; Pi, L.; Li, L.; Li, H.; Lu, J.; Zhai, T. Tunneling Diode Based on WSe2/SnS2 Heterostructure Incorporating High Detectivity and Responsivity. Adv. Mater. 2018, 30, 1703286. (38) Cheng, R. Q.; Wang, F.; Yin, L.; Wang, Z. X.; Wen, Y.; Shifa, T. A.; He, J. HighPerformance, Multifunctional Devices Based on Asymmetric van der Waals Heterostructures. Nat. Electron. 2018, 1, 356-361. (39) Zhou, X.; Hu, X. Z.; Yu, J.; Liu, S. Y.; Shu, Z. W.; Zhang, Q.; Li, H. Q.; Ma, Y.; Xu, H.; Zhai, T. Y. 2D Layered Material-Based van der Waals Heterostructures for Optoelectronics. Adv. Funct. Mater. 2018, 28, 1706587.


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Page 27 of 40 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

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(40) Wei, Q. L.; Lin, C. Q.; Li, Y. F.; Zhang, X. Y.; Zhang, Q. Y.; Shen, Q.; Cheng, Y. C.; Huang, W. Physics of Intrinsic Point Defects in Bismuth Oxychalcogenides: A First-Principles Investigation. J. Appl. Phys. 2018, 124, 055701. (41) Zhou, X.; Zhang, Q.; Gan, L.; Li, H.; Zhai, T. Large-Size Growth of Ultrathin SnS2 Nanosheets and High Performance for Phototransistors. Adv. Funct. Mater. 2016, 26, 4405-4413. (42) Choi, W.; Choudhary, N.; Han, G. H.; Park, J.; Akinwande, D.; Lee, Y. H. Recent Development of Two-Dimensional Transition Metal Dichalcogenides and Their Applications. Mater. Today 2017, 20, 116-130. (43) Wang, F. K.; Li, L. G.; Huang, W. J.; Li, L.; Jin, B.; Li, H. Q.; Zhai, T. Y. Submillimeter 2D Bi2Se3 Flakes toward High-Performance Infrared Photodetection at Optical Communication Wavelength. Adv. Funct. Mater. 2018, 28, 1802707. (44) Luo, P.; Zhuge, F. W.; Zhang, Q. F.; Chen, Y. Q.; Lv, L.; Huang, Y.; Li, H. Q.; Zhai, T. Y. Doping Engineering and Functionalization of Two-Dimensional Metal Chalcogenides. Nanoscale Horiz. 2019, 4, 26-51. (45) Wu,

M.;

Zeng,

X.

C.

Bismuth

Oxychalcogenides:

A

New

Class

of

Ferroelectric/Ferroelastic Materials with Ultra High Mobility. Nano Lett. 2017, 17, 6309-6314. (46) Moreels, I.; Lambert, K.; De Muynck, D.; Vanhaecke, F.; Poelman, D.; Martins, J. C.; Allan, G.; Hens, Z. Composition and Size-Dependent Extinction Coefficient of Colloidal PbSe Quantum Dots. Chem. Mater. 2007, 19, 6101-6106. (47) Buscema, M.; Island, J. O.; Groenendijk, D. J.; Blanter, S. I.; Steele, G. A.; van der Zant, H. S.; Castellanos-Gomez, A. Photocurrent Generation with Two-Dimensional van der Waals Semiconductors. Chem. Soc. Rev. 2015, 44, 3691-3718.


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Page 28 of 40

(48) Zhou, X.; Gan, L.; Tian, W.; Zhang, Q.; Jin, S.; Li, H.; Bando, Y.; Golberg, D.; Zhai, T. Ultrathin SnSe2 Flakes Grown by Chemical Vapor Deposition for High-Performance Photodetectors. Adv. Mater. 2015, 27, 8035-8041. (49) Xie, C.; Mak, C.; Tao, X. M.; Yan, F. Photodetectors Based on Two-Dimensional Layered Materials Beyond Graphene. Adv. Funct. Mater. 2017, 27, 1603886. (50) Fang, H.; Hu, W. Photogating in Low Dimensional Photodetectors. Adv. Sci. 2017, 4, 1700323. (51) Li, M. X.; Chen, J. S.; Routh, P. K.; Zahl, P.; Nam, C. Y.; Cotlet, M. Distinct Optoelectronic Signatures for Charge Transfer and Energy Transfer in Quantum Dot-MoS2 Hybrid Photodetectors Revealed by Photocurrent Imaging Microscopy. Adv. Funct. Mater. 2018, 28, 1707558. (52) Gough, J. J.; McEvoy, N.; O'Brien, M.; Bell, A. P.; McCloskey, D.; Boland, J. B.; Coleman, J. N.; Duesberg, G. S.; Bradley, A. L. Dependence of Photocurrent Enhancements in Quantum Dot (QD)-Sensitized MoS2 Devices on MoS2 Film Properties. Adv. Funct. Mater. 2018, 28, 1706149. (53) Raja, A.; Montoya Castillo, A.; Zultak, J.; Zhang, X. X.; Ye, Z.; Roquelet, C.; Chenet, D. A.; van der Zande, A. M.; Huang, P.; Jockusch, S.; Hone, J.; Reichman, D. R.; Brus, L. E.; Heinz, T. F. Energy Transfer from Quantum Dots to Graphene and MoS2: The Role of Absorption and Screening in Two-Dimensional Materials. Nano Lett. 2016, 16, 2328-2333. (54) Huang, Y.; Zhuge, F.; Hou, J.; Lv, L.; Luo, P.; Zhou, N.; Gan, L.; Zhai, T. Van der Waals Coupled Organic Molecules with Monolayer MoS2 for Fast Response Photodetectors with GateTunable Responsivity. ACS Nano 2018, 12, 4062-4073.


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(55) Island, J. O.; Blanter, S. I.; Buscema, M.; van der Zant, H. S.; Castellanos-Gomez, A. Gate Controlled Photocurrent Generation Mechanisms in High-Gain In2Se3 Phototransistors. Nano Lett. 2015, 15, 7853-7858. (56) Wu, J. Y.; Chun, Y. T.; Li, S.; Zhang, T.; Wang, J.; Shrestha, P. K.; Chu, D. Broadband MoS2 Field-Effect Phototransistors: Ultrasensitive Visible-Light Photoresponse and Negative Infrared Photoresponse. Adv. Mater. 2018, 30, 1705880. (57) Furchi, M.; Urich, A.; Pospischil, A.; Lilley, G.; Unterrainer, K.; Detz, H.; Klang, P.; Andrews, A. M.; Schrenk, W.; Strasser, G.; Mueller, T. Microcavity-Integrated Graphene Photodetector. Nano Lett. 2012, 12, 2773-2777. (58) Zhang, B. Y.; Liu, T.; Meng, B.; Li, X.; Liang, G.; Hu, X.; Wang, Q. J. Broadband High Photoresponse from Pure Monolayer Graphene Photodetector. Nat. Commun. 2013, 4, 1811. (59) Wang, X. M.; Cheng, Z. Z.; Xu, K.; Tsang, H. K.; Xu, J. B. High-Responsivity Graphene/Silicon-Heterostructure Waveguide Photodetectors. Nat. Photonics 2013, 7, 888-891. (60) Buscema, M.; Groenendijk, D. J.; Blanter, S. I.; Steele, G. A.; van der Zant, H. S.; Castellanos-Gomez, A. Fast and Broadband Photoresponse of Few-Layer Black Phosphorus FieldEffect Transistors. Nano Lett. 2014, 14, 3347-3352. (61) Youngblood, N.; Chen, C.; Koester, S. J.; Li, M. Waveguide-Integrated Black Phosphorus Photodetector With High Responsivity and Low Dark Current. Nat. Photonics 2015, 9, 247-252. (62) Yuan, H.; Liu, X.; Afshinmanesh, F.; Li, W.; Xu, G.; Sun, J.; Lian, B.; Curto, A. G.; Ye, G.; Hikita, Y.; Shen, Z.; Zhang, S. C.; Chen, X.; Brongersma, M.; Hwang, H. Y.; Cui, Y. Polarization-Sensitive Broadband Photodetector Using a Black Phosphorus Vertical p-n Junction. Nat. Nanotechnol. 2015, 10, 707-713.


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(63) Nian, Q.; Gao, L.; Hu, Y.; Deng, B.; Tang, J.; Cheng, G. J. Graphene/PbS-Quantum Dots/Graphene Sandwich Structures Enabled by Laser Shock Imprinting for High Performance Photodetectors. ACS Appl. Mater. Interfaces 2017, 9, 44715-44723. (64) Nikitskiy, I.; Goossens, S.; Kufer, D.; Lasanta, T.; Navickaite, G.; Koppens, F. H.; Konstantatos, G. Integrating an Electrically Active Colloidal Quantum Dot Photodiode with a Graphene Phototransistor. Nat. Commun. 2016, 7, 11954. (65) Yu, Y.; Zhang, Y. T.; Song, X. X.; Zhang, H. T.; Cao, M. X.; Che, Y. L.; Dai, H. T.; Yang, J. B.; Zhang, H.; Yao, J. Q. PbS-Decorated WS2 Phototransistors with Fast Response. ACS Photonics 2017, 4, 950-956. (66) Kang, D. H.; Pae, S. R.; Shim, J.; Yoo, G.; Jeon, J.; Leem, J. W.; Yu, J. S.; Lee, S.; Shin, B.; Park, J. H. An Ultrahigh-Performance Photodetector Based on a Perovskite-Transition-MetalDichalcogenide Hybrid Structure. Adv. Mater. 2016, 28, 7799-7806. (67) 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. (68) Schornbaum, J.; Winter, B.; Schiessl, S. P.; Gannott, F.; Katsukis, G.; Guldi, D. M.; Spiecker, E.; Zaumseil, J. Epitaxial Growth of PbSe Quantum Dots on MoS2 Nanosheets and Their Near-Infrared Photoresponse. Adv. Funct. Mater. 2014, 24, 5798-5806. (69) Lian, L. Y.; Xia, Y.; Zhang, C. W.; Xu, B.; Yang, L.; Liu, H.; Zhang, D. L.; Wang, K.; Gao, J. B.; Zhang, J. B. In Situ Tuning the Reactivity of Selenium Precursor To Synthesize Wide Range Size, Ultralarge-Scale, and Ultrastable PbSe Quantum Dots. Chem. Mater. 2018, 30, 982989.


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FIGURES AND CAPTIONS

Figure 1. Growth and characterization of high mobility 2D Bi2O2Se nanosheets. (a) The tetragonal crystal structure of Bi2O2Se. (b) Schematic illustration of the CVD growth setup for Bi2O2Se. (c) The optical microscopy image, (d) AFM image, (e) HRTEM image of as-grown Bi2O2Se, the SAED pattern of the nanosheet is displayed in the inset of (e). (f) IV characteristic of Bi2O2Se under varied back-gate modulation from -60 to 100 V and (g) the estimated electron


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mobility and concentration from field effect measurements. (h) Absorption spectra of Bi2O2Se nanosheets with different thicknesses.


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Figure 2. The assembly and characterization of Bi2O2Se/PbSe hybrid structure. (a) HRTEM image and (b) the absorption spectra of as-used PbSe CQDs solution and spin-coated film, showing an average diameter around 6.5 nm and first excitation peak around 2100 nm. Inset of (b): the photograph of dispersed PbSe CQDs in octane solution and the film spin-coated on quartz substrate. (c) Schematic illustration of the fabrication of PbSe sensitized Bi2O2Se via spin-coating processes. (d) XRD spectra, (e) TEM image, (f) HRTEM image, and (g) the EDS element mapping (Bi, Pb, O) of PbSe CQDs on Bi2O2Se, suggesting the uniform distribution of


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CQDs. In the inset of (f), the arrow indicated diffraction rings in SAED pattern is related to the randomly oriented PbSe CQDs.


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Figure 3. Determination of energy band alignment of Bi2O2Se/PbSe heterostructure. (a) UPS spectra of bare PbSe and Bi2O2Se displaying the valance band spectra and second electron cutoffs. (b) The estimated Type II energy band alignment between PbSe and Bi2O2Se before and after contact based on the estimated valance band offset and work function difference in UPS. After contact, charge transfer dipoles were expected to form at the PbSe/Bi2O2Se interface and impede to some extent electron transfer under light excitation.


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Figure 4. Broadband and fast photoresponse of PbSe/Bi2O2Se hybrid photodetector. (a) Schematic illustration of the hybrid photodetector under light excitation, inset: OM image of the as-fabricated device. (b) I-V curves of bare Bi2O2Se, PbSe and PbSe/Bi2O2Se hybrid photodetectors under dark and illumination (532 nm, 3.7 mW/cm2), and (c) their photoresponse spectra. (d) The dependence of device responsivity to light intensity at 1456 nm and 2000 nm beyond the absorption limit of Bi2O2Se. (e) shows the typical device response at 2000 nm under varied light intensities of 35 mW/cm2 to 1.34 W/cm2. (f) The distinct response decay dynamics of the hybrid photodetector under 532 nm and 2000 nm excitation compared


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to bare Bi2O2Se and PbSe CQDs. (g) Illustration of the photogating effect in the hybrid photodetector and the proposed different trap limited response dynamics at varied photo energy Ehν.

Figure 5. Field effect modulation of Bi2O2Se/PbSe hybrid detctor for 2000 nm infrared detection. (a) Schematic illustration of the FET device with Si back-gate. (b) Transfer curves of the hybrid FET under different light intensity at 2000 nm. (c) The light intensity-dependent photocurrent under varied back-gate biases, the dependence are fitted using Iph  Pα. (d) The extracted α in fitting the light intensity dependence indicates a change of photocurrent generation mechanism from photoconductive to photogate dominated behaviors under


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positive gate bias. (e) The proposed interfacial energy band diagrams illustrating the different charge separation efficiency at the heterostructure under different back-gate modulation.


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Figure 6. Responsivity of the hybrid PbSe/Bi2O2Se photodetector at 2000 nm. (a) Gate modulation to the device responsivity at different light intensity levels. (b) Comparison of the responsivity of present hybrid photodetector with other 2D infrared photodetectors based on graphene,57-59 BP,60-62 Bi2O2Se,16,20 and some typical 0D-2D hybrid infrared photodetectors like graphene/QD26,33,63,64 and TMDs/QD.28,65-68


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