High-sensitivity light detection via gate tuning of organometallic

Subscriber access provided by - Access paid by the | UCSB Libraries

Article

High-sensitivity light detection via gate tuning of organometallic perovskite/PCBM bulk heterojunctions on ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 gated graphene field effect transistors Liping Wu, Liang Qin, Yong Zhang, Mohammed Alamri, Maogang Gong, Wang Zhang, Di Zhang, Wai-Lun Chan, and Judy Z. Wu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b00996 • Publication Date (Web): 26 Mar 2018 Downloaded from http://pubs.acs.org on March 26, 2018

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.

ACS Applied Materials & Interfaces 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 23 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 Applied Materials & Interfaces

High-sensitivity light detection via gate tuning of organometallic perovskite/PCBM

bulk

heterojunctions

on

ferroelectric

Pb0.92La0.08Zr0.52Ti0.48O3 gated graphene field effect transistors Liping Wu1,2, Liang Qin1,3, Yong Zhang1,4, Mohammed Alamri1, Maogang Gong1,*, Wang Zhang2,*, Di Zhang2, Wai-Lun Chan1,* and Judy Z. Wu1,* 1. Department of Physics and Astronomy, University of Kansas, KS 66045, US 2. Department of Materials Science and Engineering, University of Shanghai JiaoTong University, Shanghai 200240, China 3. Key Laboratory of Luminescence and Optical Information, Ministry of Education, Beijing JiaoTong University, Beijing 100044, China 4. School of Microelectronics, Xi’an Jiaotong University, Xi’an, Shaanxi, 710049, China

1

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

ABSTRACT:

Organometallic

perovskite

(OMP)

CH3NH3PbI3

Page 2 of 23

doped

with

[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) has been shown to form bulk heterojunction (OMP-PCBM BHJ) for improved charge separation. In this work, the OMP-PCBM BHJ photosensitizer is combined with graphene field effect transistors (GFETs) with a ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) gate of high gating efficiency. A remarkable gate tunability via shifting the Fermi energy of graphene with respect to the valence band maximum (VBM) and conduction band minimum (CBM) of the OMP was observed which is critical to facilitating efficient charge transfer across the OMP-PCBM BHJ/GFET interface. The combination of the high-efficiency charge separation by BHJ and charge transfer by high gate tunability leads to achievement of high photoresponsivity up to 7×106 A/W and detectivity exceeding 7×1012 Jones at 550 nm at a small gate voltage of 1.0 V. These results represent almost two orders of magnitude improvement over that without a gate tuning under the similar experimental condition, illustrating the importance of the interface electronic structure in optimizing the optoelectronic performance of the OMP-PCBM BHJ/GFET devices.

KEYWORDS: organometallic perovskite, ferroelectric gate, graphene field effect transistor, bulk heterojunction.

2


Page 3 of 23 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


1. INTRODUCTION Semiconductor nanostructured sensitizer/graphene nanohybrids provide a unique scheme for photodetection with extraordinary photoconductive gain through a combination of the enhanced light-solid interaction in semiconductor nanostructures and the superior charge carrier mobility of graphene.1-8 The high photoconductive gain up to 1010 has been demonstrated in these nanohybrid devices and highly efficient charge transfer between sensitizer and the graphene is essential to the high performance. Among many sensitizers, the organometallic halide perovskites outperform due to their superior optoelectronic performances including large light absorption cross-section, high charge carrier mobility, long carrier lifetime and diffusion length.9-13 Recently, the perovskite materials with various nanostructures have been coupled with graphene for high-performance of optoelectronic devices.14-16 However, the charge transfer between perovskite materials and graphene is subjected to the band-bending between their interface.2 Hence, both the photo-excited electrons and holes in the perovskite materials may be injected into graphene depending on the interface electronic band alignment. In the case of an un-optimal interface electronic band alignment, the amount of net charges injected into graphene would be limited, resulting in low photocurrent and photoresponsivity. Therefore, improving charge transfer across the perovskite/graphene interface becomes the key to high performance optoelectronics based on the perovskite/graphene nanohybrids. Molecules such as [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) have been added to the perovskite to form bulk-heterojunctions (BHJs) that can improve the performance and 3



stability of perovskite solar cells.

17-19

Page 4 of 23

In the case of the perovskite photodetector, the BHJ

can not only help separate the photoexcited electron-hole pairs but also selectively trap electrons or holes to increase the lifetime of the charge carriers and, hence, the photoresponsivity through enhanced charge transfer to graphene. In our previous work, we have shown that the organometallic perovskite CH3NH3PbI3 mixed with PCBM in a bulk heterojunction (OMP-PCBM BHJ) nanohybrid device indeed has improved charge separation efficiency, charge carrier lifetime, and photoresponsivity.

20

Apart from this method, we

demonstrate in this work that the gate tuning of the interface electronic structure can facilitate highly efficient charge transfer between the OMP-PCBM BHJ and the graphene. This can be realized by fabricating the OMP-PCBM BHJ sensitizer film onto Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) gated graphene field effect transistors (GFETs). PLZT is a ferroelectric materials with extraordinarily high dielectric permittivity around 1300, as well as high breakdown field of 2.0 MV cm-1.

21, 22

This allows high-efficiency bipolar doping of GFETs with a small

back-gate voltage (Vbg) of ~±1-2 V, which is beneficial to practical applications. In addition, PLZT has a suitable Cuire temperature around 180 oC, preventing phase change from ferroelectric to dielectric under the thermal budget of 150 oC, which is typically applied for fabrication of GFET/PLZT-gate devices. The highest photoresponsivity acquired from the OMP-PCBM BHJ/GFET devices was 7×106 A/W, with a D* of 7×1012 Jones, and the corresponding photoconductive gain is up to 108. These results are almost two orders of magnitude higher than that of the OMP-PCBM BHJ/graphene device at the same experimental condition without gate tuning, 20 illustrating gate tuning as an effective approach to enhance the optoelectronic performance of

OMP-PCBM BHJ/GFET devices. 4


Page 5 of 23 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


2. EXPERIMENTAL SECTION Fabrication of PLZT gated GFETs: The PLZT films were fabricated on conductive 1.4% Nd-doped (001) SrTiO3 (Nb:STO) (as the back gate electrode) using pulsed laser deposition (PLD). The details of the fabrication and characterization of the microstructure, morphology, and ferroelectric/dielectric properties of the PLZT films have been reported previously. 21, 22 Briefly, high-quality epitaxial PLZT films with a thickness of 500 nm were deposited at 650 o

C substrate temperature in 220 mTorr oxygen partial pressure. The laser energy density on

the PLZT target was about 2.0 J/cm2 with laser repetition rate of 10 Hz. After PLD, the PLZT films were in situ post-annealed at 650 oC for 30 min in 600 Torr oxygen pressure to optimize the oxygen content before naturally cooling down to room temperature. The measured dielectric constant of the PLZT film is typically larger than 1000, which provides high-efficiency gating to the GFETs. Chemical vapor deposition was applied for synthesis of single layer graphene on commercial copper foils (Sigma-Aldrich, USA) at 1000 oC. The details of the CVD process has been reported previously.3, 4 After the synthesis, graphene samples of a typical dimension of 1×1 cm2 was transferred onto the PLZT films using a similar procedure reported in our previous works and a two-step lithography process was applied for GFET fabrication.1 In the first photolithography, source and drain electrodes were defined, followed with electron-beam evaporation of 2 nm titanium/88 nm gold. The second photolithography was applied to define the GFET channel of 7.0 µm in length and 13 µm in width and the rest of the graphene was removed with oxygen plasma in a reactive ion etcher (RIE, Torr International). The RIE time was 150 s under 6.7 mTorr oxygen partial pressure at 20 W RF power. Through this method, 5



the graphene channel of the samples measured can scale down from several micrometers to tens of micrometers. Fabrication of perovskite/PCBM bulk heterojunctions: The CH3NH3PbI3 precursor solution was prepared by dissolving the lead iodide (Alfa Aesar, 99.9985%) and Methylammonium iodide (Luminescence technology, 99.5%) in a stoichiometric ratio in DMF (Sigma-Aldrich, 99.8%) with a concentration of 0.75 M. The solution was stirred at 70 oC overnight before cooling down to room temperature for spin-coating. For OMP CH3NH3PbI3 mixed with PCBM, PCBM (Luminescence technology, 99.5%) was mixed into the perovskite solution with a weight ratio of 0.1%. Specifically, PCBM was dissolved into chlorobenzene first, and then mixed with perovskite solution. The same volume of chlorobenzene was added into the pure perovskite solution for the 0% PCBM control device. The perovskite film was deposited on a pre-heated (at 80 oC) graphene substrate by spin-coating at 500 rpm for 30 s and 3000 rpm for 60 s in a nitrogen flowing glovebox. During the spin-coating, the anti-solvent was dropped to crystallize. Then the perovskite film was annealed at 70 oC for 20 min and 100 oC for 10 min to remove the residual solvent. The average film thickness is around 380 nm under this condition. 4 Characterization of the OMP-PCBM BHJ/GFET devices: The Raman spectra of the perovskite/graphene samples were measured with a laser wavelength of 488 nm and laser power of about 1 mW. The integration time and average time were 2s and 10s, respectively. The electronic and optoelectronic properties including I−V characteristics, noise, and dynamic photoresponse of the OMP-PCBM BHJ/GFET devices were measured using a xenon lamp as the light source and an Agilent B1505A semiconductor device analyzer. The 6


Page 6 of 23

Page 7 of 23 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


output optical power at the sample was calibrated using an optical power meter connected to a Si photodiode (Oriel Apex, Newport). The reference diode was traceable to NREL certification. The noise spectra were measured via a Stanford Research SR760 spectrum analyzer and an Agilent E3631A voltage source. 3. RESULTS AND DISCUSSION Figure 1(a) illustrates schematically the source, drain and back-gate electrodes of an OMP-PCBM BHJ/GFET photodetector. The source-drain current (Isd) can be taken in dark (Idark) and under illumination of light (Ilight) at different Vbg’s. The physical structure and charge transfer process in the BHJ/graphene layer under light illumination is demonstrated in Figure 1(b). As the schematic energy diagram in Figure 1(c) indicates that, upon absorption of photons with energy exceeding the bandgap of the perovskite at about 1.5 eV, electron-hole pairs will be generated in the photoactive perovskite layer. The separation of the electron-hole pairs will then be accelerated with the help of the OMP-PCBM BHJs. PCBM is an electron acceptor and can effectively trap electrons when the holes are injected into the graphene channel. The trapped electron will generate photo-gating effect on the GFET typically illustrated as the shift of the Dirac point (VDirac, defined at the minimum GFET conductance) towards positive side, which is observed in our photodetector. The enhanced electron life time due to charge trapping by PCBM 20 and short charge transit time through the GFET channel lead to high photoconductive gain and therefore high detectivity D* as we shall discuss in the following. Figure 1(d) shows the Raman characteristic peaks of graphene channel on PLZT at~1582 cm-1 and ~2678 cm-1 corresponding to the G and 2D bands, respectively. The G peak 7



Page 8 of 23

corresponds to the primary in-plane vibrational mode (E2g phonon mode) and the 2D peak is the second order of the D peak that corresponds to A1g breathing mode 20. Figures 2(a, d) depict the Isd - Vbg curves measured on OMP/GFET (without PCBM) and OMP-PCBM HBJ/GFET devices, respectively. In both cases, a systematic right shift of the Isd - Vbg curves with increasing light intensity can be observed. This shift can be attributed to the photo-gating effect on the GFET due to the hole transfer from the OMP to graphene as explained in Figure 1(c) due to the band edge alignment across the interface at OMP/GFET with and without PCBM. As a consequence of the hole transfer, the electrons accumulate in the BHJ layer before charge recombination occurs. This leads to an effective negative gate voltage and induce positive carriers in the graphene channel through capacitive coupling. This so-called photo-gating effect explains the observed right shift of Dirac point toward positive gate voltage when increasing the incidence light power.

7,

8,

21-23

The

photoresponsivity (R) of the device can be estimated from the following formula: 24 =

(1)

Where Pin is light power incident to the GFET channel. Figures 2(b, e) depict the calculated R vs. Vbg curves of the two devices in Figures 2(a, d), respectively, at different Pin values of 4.5 µW/cm2 (red), 10.0 µW/cm2 (blue) and 17.5 µW/cm2 (orange). For both devices, a maximum photoresponsivity can be obtained at the lowest Pin. The monotonically decreasing R with the increasing Pin can be attributed to the increasing charge carrier recombination in the perovskite film at higher photo-carrier concentrations. In addition, the built-in electric field produced by the accumulated electrons in the BHJs will also hinder the diffusion of holes to the graphene channel. The maximum photoresponsivity attained by OMP-PCBM BHJ/GFET 8


Page 9 of 23 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


device is 1.0×105 A/W with a Vsd= 0.01 V, which is nearly three times that of the pure OMP/GFET device without PCBM. Besides, a strong tuning of the R through Vbg can be clearly seen in both

devices. Quantitatively, the gate tunability has different behaviors in the

two cases. On the OMP/GFET device without PCBM doping, the maximum R (3.3×104 A/W) occurs at Vbg=0.25 V (on the right side of the Dirac point), while the R decreases at slightly higher or lower Vbg. In comparison with the R ~ 3.1×104 A/W at Vbg=0, the benefit of the gate tunability estimated from (Rmax –RVbg=0)/RVbg=0 is only few percent without BHJs. In contrast, significantly enhanced gate tunability can be obtained in presence of the BHJ. While a similar trend of a much higher R also occurs on the right side of the Dirac point on the OMP-PCBM BHJ/GFET device in Figure 2(e), considerably higher R values are observed due to the formation of the BHJs in the OMP-PCBM sensitizer. The largest R enhancement by the BHJ occurs at the lowest Pin=4.5 µW/cm2 (red). Interestingly, the R peak shown in the OMP/GFET case in Figure 2(b) cannot be observed within the Vbg range up to 1.0 V. Instead, a monotonic increasing R with Vbg is illustrated in Figure 2(e) for the OMP-PCBM BHJ/GFET devices. The highest R ~1.0×105 A/W at Vbg=1.0 V is three times higher than the R peak of 3.3×104 A/W in Figure 2(b) for the OMP/GFET device, and higher R can be projected at higher Vbg beyond Vbg=1.0 V. This means the gate tunability of the R value is more than 70% due to the BHJs in the OMP-PCBM BHJ/GFET devices, which is more than an order of magnitude higher than that without BHJs. Considering the only difference in the OMP/GFET and OMP BHJ/GFET devices is the addition of PCBM that leads to enhanced exciton life time and therefore reduced charge recombination, enhanced carrier transfer across the OMP BHJ/GFET interface and hence photo-gating effect is anticipated in the latter. 9



Page 10 of 23

It should be noted that the Vsd can provide further tuning on the R values by reducing the carrier transit time (Ttransit) since Ttransit (carrier drift velocity) decreases (increases) linearly with the increasing Vsd. Figures 2(c) and 2(f) demonstrate the R vs. Vbg of pure perovskite and OMP-PCBM BHJ/GFET devices at different Vsd of 10 mV, 50 mV and 100 mV, respectively. The observed monotonic increasing R values linearly with increasing Vsd is therefore anticipated due to the higher photoconductive gains at higher Vsd biases. The dynamic photoresponse of the two devices were recorded under on/off light cycles (wavelength 500 nm; intensity 50 µW/cm2) at Vbg= 0 V, as shown in Figures 3(a) and 3(b). The Iph/Idark ratios for the devices without and with the PCBM doping are comparable, with a value of 1.3 and 1.7, respectively. An asymmetric pattern, i.e. a shorter rising time and a longer falling time can be observed for both devices. The rise/fall time constants can be estimated based the durations between 0% to 70% of the peak current value. They are 12 s/35 s, 16 s/68 s, for the OMP/GFET and OMP-PCBM BHJ/GFET devices, respectively. With the formation of BHJs, electrons were trapped by the BHJ and hence had a longer lifetime compared with the case of without BHJs. Figures 3(c)-(d) demonstrate the spectral photoresponsivity and external quantum efficiency (EQE) curve of the OMP/GFET and OMP-PCBM BHJ/GFET devices respectively. The EQE was calculated using the following formula: 25 =

= 1243 ×

×

(2)

where Nelectron, Nphoton and λ are the number of photoelectron, number of incident photon and wavelength of incident light, respectively. The spectral behavior of the two devices are similar while both the spectral photoresponsivity and EQE of device with 0.1% are higher 10


Page 11 of 23 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


than that of 0%. A band edge between 750 nm and 800 nm can be observed, which is corresponding well to the expected cut-off wavelength of perovskite at 780 nm. Figure 4(a) depicts the R vs Pin curves of the two devices under different Vbg, 0 V, 0.25 V and 1 V, respectively. As explained earlier, the R values of the two devices increase monotonically with the decreasing incident light power, since higher light intensity leads to higher carrier concentration and hence a higher electron-hole recombination rate. Interestingly, the R vs. Pin curves of the OMP-PCBM BHJ/GFETs have larger slopes (absolute value), which results in the higher R values than in the OMP/GFETs at lower Pin. At the lowest Pin of 4x10-11 W, the highest R acquired for OMP/GFET device is 3.3×105 A/W (the R peak at Vbg=0.25 V), while for OMP-PCBM BHJ/GFET device, it is 1.0×106 A/W at Vbg=1 V and could be further enhanced at a larger Vbg. This result is almost two orders higher than that of the OMP-PCBM BHJ device in our previous work with the same incident light intensity, while the Vsd is one order lower than the latter. 20 In addition, the implementation of the BHJs in the sensitizer enables larger tunability of the Vbg to up to 800% at Pin near 4x10-10 W. This is in contrast to ~200% for the OMP/GFETs. Figure 4(b) shows the R vs Vsd curves of the two devices under different incident light power, 4.5 µW/cm2, 10.0 µW/cm2 and 17.5 µW/cm2, respectively. The R values of the both devices increase monotonically with the Vsd. As the Vsd is increased from 0.01 V to 0.1 V, the R values also increase by an order of magnitude, which is anticipated from the enhanced photoconductive gains at an enhanced charge drift velocity (see details below). To further demonstrate the tunability of the Vsd , Figure 4(c) depicts the R vs. Vsd curve with the Vsd range extended to 700 mV. Remarkably, R values increase linearly with Vsd as expected and reach at 7.0×106 A/W at Vsd =0.7 V, which 11



Page 12 of 23

can be attributed to the higher photoconductive gain (to be discussed in the following) due to the shorter charge transit time across a shorter GFET channel of a few micrometer length. While R value~7.0×106 A/W obtained in the OMP-PCBM BHJ/GFET device is comparable to the best so far reported for OMP-based photodetectors (based on the R’ values under a comparable Pin in Table 1 since R depends on Pin pretty sensitively), it should be mentioned that the Vbg of 1.0 V of this work is significantly lower by more than an order of magnitude than that in the prior report. The figure-of-merit detectivity (D*) is depicted in Figure 4(d) for the OMP-PCBM BHJ/GFET device at the fixed Vbg = 1 V under different Vsd’s of 0.01 V, 0.05 V and 0.1 V (open symbols) and different Pin of 4.5 µW/cm2, 10.0 µW/cm2 and 17.5 µW/cm2 (solid symbols). The D* can be expressed by the following formula: 26

R

D* =

in where in

2

1 22

1

× A 2 (Jones)

(3)

is the mean square noise current, which can be calculated from the spectral

density of the noise power, and A is the active area of the device in cm2. The mean square noise current is proportional to

can be fitted as in 2 ∝

1 in the low frequency range from 0 Hz to few kHz, which f

1 (Figure S1). As shown in Figure 4(d), the highest D* calculated for f

the OMP-PCBM BHJ/GFET device 7.0×1012 Jones at Vbg =1.0 V, Vsd =0.7 V and Pin =4.5 µW/cm2. This performance is among the best so far reported for the OMP-based photodetectors. The photoconductive gain is typically determined by the ratio of the charge carrier lifetime in the OMP-PCBM BHJ layer (Tlife) and the transit time (Ttransit) in the graphene 12


Page 13 of 23 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


channel, which can be expressed by the following formula: 11

G=

Tlife Ttransit

=

Tlife 2

L µ −1Vsd −1

(4)

where L is the graphene channel length of the GFET device; μ is the charge carrier mobility; Vsd is the source-drain voltage. For the OMP-PCBM BHJ/GFET device, with L=7.0 μm, Vsd =0.1 V and µ ~ 53.6 cm2 V−1 s−1, the Ttransit is estimated to be ~90 ns. The lifetime of the photoexcited charge carriers can be extracted from Figure 3(b), which yields Tlife ~ 30 s. Therefore, a photoconductive gain of ~ 108 was obtained for the OMP-PCBM BHJ/GFET device based on equation (3), which is twice of that on OMP/GFETs and about two orders higher than that of the OMP-PCBM BHJ device without gate tuning in our previous work. 20 This D* is among the highest ones reported for OMP-based photodectors. The high photoconductive gain contributes primarily to the high R and D* in the OMP-PCBM BHJ/GFETs. 4. CONCLUSIONS In conclusion, through a comparative study of the OMP-PCBM BHJ/GFET and OMP/GFET photodetectors, we have demonstrated that the formation of BHJs in the OMP sensitizer can significantly increase the charge separation efficiency and charge transfer from the sensitizer to graphene tunable in a wide range of the Vbg. Intriguingly, the R vs Vbg curves for these two types of devices follow qualitatively different trends. In contrast to an R peak at Vbg ~ 0.25 V in the OMP/GFET, the R increases monotonically with Vbg in the OMP-PCBM BHJ/GFETs. An additional tunability was provided by shortening the charge transit time across the graphene channel of a short length of a few micrometers with high drift spend enabled by a 13



large Vsd. The obtained R up to 7. 0 ×106 A/W and D*~7.0x1012 Jones for the OMP-PCBM BHJ/GFET devices represent the best so far achieved on OMP-based photodetectors at a low Vbg ~ 1.0 V and the tunability demonstrated in this work using GFET parameters indicates the performance can be improved. FIGURES

Figure 1. (a) Schematic illustration of the OMP-PCBM BHJ/GFET device. (b) The PCBM is filled in the perovskite grain boundaries and played the role of acceptor, which has been studied in previous work. 20 (c) The electronic structure diagram of graphene, perovskite and PCBM. (d) Raman spectra of graphene channel and OMP-PCBM BHJ/graphene channel on PLZT substrate.

14


Page 14 of 23

Page 15 of 23 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


Figure 2. (a) - (d) Isd - Vbg curves of the OMP/GFET device and the OMP BHJ/GFET devices without/with illumination at different light intensity, respectively. (b) and (e) are R of the OMP/GFET device and the OMP-PCBM BHJ/GFET device versus Vbg under different light illumination, respectively. (c) and (f) are R versus Vbg at different Vsd for the OMP/GFET device and the OMP-PCBM BHJ/GFET device, respectively. The absolute value of the R was used in Figures 2(b)-(c), (e)-(f) in order to better present the magnitude of the photoresponse.

15



Figure 3. (a) and (b) are dynamic responses of the OMP/GFET device and the OMP-PCBM BHJ/GFET device, respectively. The data were measured under the illumination of 500 nm light with an intensity of 50 μW/cm2.(c) and (d) are spectral responses of the OMP/GFET device and the OMP-PCBM BHJ/GFET device from wavelength 400 nm to 1000 nm, respectively.

16


Page 16 of 23

Page 17 of 23 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


Figure 4. (a) R versus the power of incident light of the OMP/GFET and the OMP-PCBM BHJ/GFET devices under different Vbg. (b) R versus Vsd of the OMP/GFET and OMP-PCBM BHJ/GFET devices under different Vbg. (c) R versus Vsd of the OMP-PCBM BHJ/GFET device under four different Vsd, with an incident power of 1.2 µW/cm2. (d) Detectivity D* versus power of incident light under three different Vsd, and D* versus Vsd under different incident power of OMP-PCBM BHJ/GFET device. The Vbg applied is 1.0 V.

17



Page 18 of 23

Table 1. Performance Comparison of OMP Nanostructure based Photodetectors a,b,c

Structure

Rise time

OMP-PCBM BHJ/GFET

a

Fall time

Vsd

Pin

Vbg 2

(s)

(s)

(V)

(/cm )

(V)

16

68

0.7

1.2μW

1

R (A/W)

R’ (A/W)

7.0×10

6 5

~3.5×10

7.0×10

6

OMP-PCBM BHJ/G

49

226

1.0

3.3nW

0

1.0×10

OMP nanofilms/G

0.087

0.54

0.1

1μW

0

1.8x10

2

~1.5x10

OMP nanowires

0.02

0.014

0.3

4.6mW

NA

3.5x10

2

NA

OMP nanowires/G

55

75

0.01

65nW

0

2.6x10

6

~5x10

OMP single crystal

2.5x10

2.5x10

4.0

~1.1μW

NA

5x10

OMP-P3HT/GFET

1

25

0.1

14.15nW

-25

1.4x109

MPbBr2I islands/G

0.12

0.75

1.0

1.05nW

0

6x10

-5

-5

3

5

Ref This work

3

20

2

27 13

5

9

~5x10

3

16

~1.0x107

13

NA

28

Note: R’ refers to the estimated photoresponsivity of these devices with the same incidence light power (1.2 μW/cm2) as

the OMP-PCBM BHJ/GFET device used in this work. b c

Note: G refers to graphene.

Note: NA means not available.

ASSOCIATED CONTENT

AUTHOR INFORMATION Corresponding Author *Email: [email protected] (M. G.); [email protected] (J. W.); [email protected] (W. Z.); [email protected] (W. C.)

Notes The authors declare that there are no competing financial interests. Acknowledgement This work was supported by US National Science Foundation grants DMR-1351716, DMR-1337737, and DMR-1508494 and Army Research Office grant W911NF-16-1-0029. The investigation was also supported by the University of Kansas General Research Fund allocation #2151080. 18


Page 19 of 23 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


REFERENCES (1) Gong, M. G.; Adhikari, P.; Gong, Y. P.; Wang, T.; Liu, Q. F.; Kattle, B.; Ching, W. Y.; Chan, W. L.; Wu, J. Z. Polarity-Controlled Attachment of Cytochrome C for High-Performance Cytochrome C/Graphene Van Der Waals Heterojunction Photodetectors. Adv. Funct. Mater. 2017, 1704797. (2) Konstantatos, G.; Badioli, M.; Gaudreau, L.; Osmond, J.; Bernechea, M.; de Arquer, F. P. G.; Gatti, F.; Koppens, F. H. L. Hybrid Graphene-Quantum Dot Phototransistors with Ultrahigh Gain. Nat. Nanotechnol. 2012, 7 (6), 363-368. (3) Bonaccorso, F.; Sun, Z.; Hasan, T.; Ferrari, A. C. Graphene Photonics and Optoelectronics. Nat. Photonics 2010, 4 (9), 611-622. (4) Park, J.; Ahn, Y. H.; Ruiz-Vargas, C. Imaging of Photocurrent Generation and Collection in Single-Layer Graphene. Nano Lett. 2009, 9 (5), 1742-1746. (5) Koppens, F. H. L.; Mueller, T.; Avouris, P.; Ferrari, A. C.; Vitiello, M. S.; Polini, M. Photodetectors Based on Graphene, Other Two-Dimensional Materials and Hybrid Systems. Nat. Nanotechnol. 2014, 9, 780-793. (6) Gong, M.; Liu, Q.; Cook, B.; Kattel, B.; Wang, T.; Chan, W. L.; Ewing, D.; Casper, M.; Stramel, A.; Wu, J. Z. All-Printable Zno Quantum Dots/Graphene Van Der Waals Heterostructures for Ultrasensitive Detection of Ultraviolet Light. ACS Nano 2017, 11 (4), 4114-4123. (7) Xia, F. N.; Mueller, T.; Lin, Y. M.; Valdes-Garcia, A.; Avouris, P. Ultrafast Graphene Photodetector. Nat. Nanotechnol. 2009, 4 (12), 839-843. (8) Gong, M.; Liu, Q.; Goul, R.; Ewing, D.; Casper, M.; Stramel, A.; Elliot, A.; Wu, J. Z.

19



Printable Nanocomposite FeS2-PbS Nanocrystals / Graphene Heterojunction Photodetectors for Broadband Photodetection. ACS Appl. Mater. Interfaces 2017, 9, 27801–27808. (9) Spina, M.; Lehmann, M.; Nafradi, B.; Bernard, L.; Bonvin, E.; Gaal, R.; Magrez, A.; Forro, L.; Horvath, E. Microengineered CH3NH3PbI3 Nanowire/Graphene Phototransistor for Low-Intensity Light Detection at Room Temperature. Small 2015, 11 (37), 4824-8. (10) Sun, Z. H.; Aigouy, L.; Chen, Z. Y. Plasmonic-Enhanced Perovskite-Graphene Hybrid Photodetectors. Nanoscale 2016, 8 (14), 7377-7383. (11) Kwak, D. H.; Lim, D. H.; Ra, H. S.; Ramasamy, P.; Lee, J. S. High Performance Hybrid Graphene-CsPbBr3-XIx Perovskite Nanocrystal Photodetector. RSC Adv. 2016, 6 (69), 65252-65256. (12) Dang, V. Q.; Han, G. S.; Trung, T. Q.; Duy, L. T.; Jin, Y. U.; Hwang, B. U.; Jung, H. S.; Lee, N. E. Methylammonium Lead Iodide Perovskite-Graphene Hybrid Channels in Flexible Broadband Phototransistors. Carbon 2016, 105, 353-361. (13) Xie, C.; Yan, F. Perovskite/Poly(3-Hexylthiophene)/Graphene Multiheterojunction Phototransistors with Ultrahigh Gain in Broadband Wavelength Region. ACS Appl. Mater. Interfaces 2017, 9 (2), 1569-1576. (14) Nie, W. Y.; Tsai, H. H.; Asadpour, R.; Blancon, J. C.; Neukirch, A. J.; Gupta, G.; Crochet, J. J.; Chhowalla, M.; Tretiak, S.; Alam, M. A.; Wang, H. L.; Mohite, A. D. High-Efficiency Solution-Processed Perovskite Solar Cells with Millimeter-Scale Grains. Science 2015, 347 (6221), 522-525. (15) Green, M. A.; Ho-Baillie, A.; Snaith, H. J. The Emergence of Perovskite Solar Cells. Nat. Photonics 2014, 8 (7), 506-514. 20


Page 20 of 23

Page 21 of 23 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


(16) Xing, G.; Mathews, N.; Sun, S.; Lim, S. S.; Lam, Y. M.; Gratzel, M.; Mhaisalkar, S.; Sum,

T.

C.

Long-Range

Balanced

Electron-

and

Hole-Transport

Lengths

in

Organic-Inorganic CH3NH3PbI3. Science 2013, 342 (6156), 344-347. (17) Zhang, F.; Shi, W.; Luo, J.; Pellet, N.; Yi, C.; Li, X.; Zhao, X.; Dennis, T. J. S.; Li, X.; Wang, S.; Xiao, Y.; Zakeeruddin, S. M.; Bi, D.; Gratzel, M. Isomer-Pure Bis-PCBM-Assisted Crystal Engineering of Perovskite Solar Cells Showing Excellent Efficiency and Stability. Adv. Mater. 2017, 29, 1606806 (18) Xu, J.; Buin, A.; Ip, A. H.; Li, W.; Voznyy, O.; Comin, R.; Yuan, M.; Jeon, S.; Ning, Z.; McDowell, J. J.; Kanjanaboos, P.; Sun, J. P.; Lan, X.; Quan, L. N.; Kim, D. H.; Hill, I. G.; Maksymovych, P.; Sargent, E. H. Perovskite-Fullerene Hybrid Materials Suppress Hysteresis in Planar Diodes. Nat. Commun. 2015, 6, 7081. (19) Chiang, C.-H.; Wu, C.-G. Bulk Heterojunction Perovskite–PCBM Solar Cells with High Fill Factor. Nat. Photonics 2016, 10 (3), 196-200. (20) Qin, L.; Wu, L.; Kattel, B.; Li, C.; Zhang, Y.; Hou, Y.; Wu, J.; Chan, W.-L. Using Bulk Heterojunctions and Selective Electron Trapping to Enhance the Responsivity of Perovskite-Graphene Photodetectors. Adv. Funct. Mater. 2017, 27 (47), 1704173. (21) Ma, C.; Gong, Y.; Lu, R.; Brown, E.; Ma, B.; Li, J.; Wu, J. Detangling Extrinsic and Intrinsic Hysteresis for Detecting Dynamic Switch of Electric Dipoles Using Graphene Field-Effect Transistors on Ferroelectric Gates. Nanoscale 2015, 7, 18489-18497. (22) Ma, C.; Lu, R.; Hu, G.; Han, J.; Liu, M.; Li, J.; Wu, J. Detecting Electric Dipoles Interaction at the Interface of Ferroelectric and Electrolyte Using Graphene Field Effect Transistors. ACS Appl. Mater. Interfaces 2017, 9 (4), 4244-4252. 21



(23) Hu, G.; Pandey, G. P.; Liu, Q.; Anaredy, R. S.; Ma, C.; Liu, M.; Li, J.; Shaw, S. K.; Wu, J. Z. Self-Organization of Ions at the Interface between Graphene and Ionic liquid DEME-TFSI. ACS Appl. Mater. Interfaces 2017, 9(40), 35437-35443. (24) Rogalski, A., Infrared Detectors (Second Version). CRC Press, Boca Raton, 2010. (25) Garrido, J. A.; Monroy, E.; Izpura, I.; Muoz, E. Photoconductive Gain Modelling of GaN Photodetectors, Semicond. Sci. Technol. 1998, 13, 563-568. (26) Liu, X.; Gu, L.; Zhang, Q.; Wu, J.; Long, Y.; Fan, Z. All-printable Band-Edge Modulated ZnO Nanowrie Photodetectors with Ultra-High Detectivity. Nat. Commun. 2014, 5, 4007. (27) 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 (1), 41-6. (28) Wang, Y.; Zhang, Y.; Lu, Y.; Xu, W.; Mu, H.; Chen, C.; Qiao, H.; Song, J.; Li, S.; Sun, B.; Cheng, Y.-B.; Bao, Q. Hybrid Graphene-Perovskite Phototransistors with Ultrahigh Responsivity and Gain. Adv. Optical Mater. 2015, 3 (10), 1389-1396.

22


Page 22 of 23

Page 23 of 23 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


Toc Figure:

23


High-sensitivity light detection via gate tuning of organometallic

Recommend Documents