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Abstract
The monolithic stacked design is expected to solve the challenges of wiring difficulties, complex fabrication processes, and low resolution. However, a photodetector array with low operating voltage that is suitable for imaging applications has not been proposed. Here, a perovskite photodetector array with a monolithic stacked structure is proposed. The CH3NH3PbI3 photodetector has a low power consumption off-state (0 V) and on-state (−2 V) voltage, and the highest responsivity and specific detectivity of 0.39 A/W and 4.53×1012 Jones at 775 nm, respectively. The rise time and decay time are 111 µs and 250 µs respectively. In addition, the imaging application shows high contrast, which provides a simple and effective way to prepare high performance perovskite imaging devices.
© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1. Introduction
As a device that can convert light signals into electrical signals, photodetectors (PDs) are widely used in communication, industrial automatic control and image sensing [1–3]. PDs used in imaging need to meet a number of requirements, high responsivity, fast response speed, large linear range, and low operating voltage, for the sake of weak lighting conditions, record moving objects, high contrast ratio, and low power consumption [4]. Compared with single PD scanning imaging, PD array imaging has obvious advantages in speed, consumption and size [5–12]. In order to acquire data from every PD in array, each pixel needs a switch, usually a transistor, to avoid crosstalk. However, arraying and patterning will lead to complex fabrication process and inevitably introduce a large number of wires, which occupy the reading resources.
Vertical designed photodiode array can greatly reduce the number of wires, but it is impossible to apply an off-state voltage to turn off non-working pixels, resulting in circuit crosstalk, which cannot be applied to imaging. Therefore, it is necessary to develop a PD that retains the advantages of vertical structure and can be turned off by a bias.
Previously, a monolithic stacked design of photodiode and rectify diode based on P3HT: PCBM was proposed by Takao et al., which effectively makes pixels turn off normally, reduces crosstalk and fabrication difficulty, eventually realizes two-terminal imaging [13,14]. However, due to the low extinction coefficient and short carrier diffusion length of organic polymers, this kind of device usually has low responsivity. Although the photoelectric multiple technique is used to improve the responsivity, it still need to apply a high operating voltage (20 V), which is not contribute to the development of small-sized, wearable devices [15]. Perovskite has attracted attention as a photoelectric material with high light absorption coefficient, adjustable band gap, long carrier life and diffusion length, and simple synthetic method [16,17]. Typically, researchers take advantage of interface modulator to improve the performance of perovskite solar cells and PDs [18–21]. Perovskite PDs have made great progress in recent years. Such as narrow-band PDs without filter and self-driven PDs without applied bias [22–27]. However, how to obtain low operating voltage and high-performance perovskite PDs with monolithic stacked design is still a problem to be solved.
Here, we propose monolithic stacked perovskite PDs based on CH3NH3PbI3 (MAPbI3) and CH3NH3PbI3-xClx (MAPbI3-xClx) prepared by one- and two-step processes, respectively. For MAPbI3 device, the responsivity and specific detectivity can reach 0.39 A/W and 4.53×1012 Jones (Jones = cm Hz1/2 W−1) in 300-800 nm at −2 V operating voltage, the rise time and decay time are 111 µs and 250 µs respectively. Moreover, the pixels can still keep the off-state under the illumination at 0 V and high contrast image can be obtained for the 8×8 PD array. This work has a potential in low-power image sensors, and is expected to solve the challenge of high-resolution.
2. Experimental section
2.1 Materials
N, N-dimethylformamide (DMF, 99.8%), dimethyl sulfoxide (DMSO, 99.9%), chlorobenzene (CB, 99.5%), pentacene (98%) and ethyl acetate (EA, 99.8%) were purchased from Aladdin. Aqueous colloidal Tin (IV) oxide suspension (SnO2, 15% in H2O) was purchased from Alfa Aesar. Lead (II) iodide (PbI2, 99.9%), lead (II) chloride (PbCl2, 99.9%), methylammonium iodide (MAI, 99.5%) were purchased from Xi’an Polymer Light Technology Corp. All the chemicals were used as received without further purification.
2.2 Synthesis of the MAPbI3 precursor
PbI2 and MAI were dissolved in 1 mL mixed solvent (DMF : DMSO=9 : 1) at an equimolar ratio of 1 : 1.05 (922 : 333.9 mg). An oscillator is used until mixed solvent dissolves completely. Then 0.22 µm PTFE filter was used to obtain the yellow transparent solution.
2.3 Device fabrication
ITO glass substrate was washed with detergent, deionized water, acetone and isopropanol for 10 min, separately. Ultraviolet ozone was treated for 15 min after drying with nitrogen flow. SnO2 NPs (diluted to 7.5%) aqueous solution was spin-coated on ITO substrate at 3000 rpm for 30 s, followed by 150 °C annealing for 1 h, and the final thickness was about 70 nm. The substrate was placed in a N2 glove box. For one-step process, MAPbI3 precursor solution was spin-coated at 6000 rpm for 30 s. Then dynamic dropping of EA (250 µL) onto the substrate at 8 s, annealed in air at 100 °C for 15 min to form the perovskite film. For two-step process, according to the method in the literature [28], PbI2: PbCl2 was dissolved in DMF at an equimolar ratio, and the precursor of PbICl was spin-coated on the substrate in a N2 glove box at 5000 rpm for 30 s, dried at 60 °C for 10 min. After cooling down to room temperature, the substrate was loaded with MAI isopropanol solution (40 mg/mL) for 40 s, then spin-coated at 4000 rpm for 30 s, and annealed at 105 °C in air for 1 h. The prepared perovskite film substrate was put into the glove box again. PTAA was dissolved in chlorobenzene solution (15 mg/mL) and spin-coated at 6000 rpm for 40 s, heated at 110 °C for 10 min, and the final thickness was about 50 nm. Finally, Pentacene, NaF and Al were evaporated 120 nm, 1 nm and 100 nm.
2.4 Device characterization
The phase of perovskite films was characterized by X-ray diffraction (D8 advance, Brucker). The surface and cross-section morphology of perovskite and device were characterized by scanning electron microscope (SU8020, Hitachi). In the electrical performance measurement, we use the Keithley 2400 source meter and the homemade probe table to measure the current-voltage relation. A 532 nm laser with a beam expander and neutral density filter were used to obtain uniform light of different intensities, and a chopper (SR540, Stanford Research) was used to obtain a modulated light. An oscilloscope (TDS2022C, Tektronix) was used to measure the response time of the device. Perovskite absorption and spectral response of device were measured by a monochrome spectrometer (Omni-λ300, Zolix) and a halogen lamp (DC mode). In the imaging application, 530 nm collimated beam LED (M530L4, Thorlabs) as the light source, and the image was obtained by scanning through a homemade circuit system as shown in Fig. S1. For example, select a row to apply a bias of −2 V, and the unselected lines were grounded, while reading current of a column to obtain the data of the crossed pixel.
3. Results and discussion
The structure of the PD is shown in Fig. 1(a). The whole structure is composed of a perovskite photodiode and a pentacene rectify diode, which use indium tin oxide (ITO) as cathode and NaF modified Al electrode as low work function anode respectively. For the photodiode, it uses a conventional structure similar to that in solar cells, SnO2 nanoparticles (NPs) are used as an electron transport layer (ETL) and poly(triarylamine) (PTAA) as hole transport layer (HTL). SnO2 NPs are widely used in perovskite solar cells due to the excellent transmission, appropriate band gap and high electron mobility [29]. The addition of potassium ions can promote the passivation of grain boundaries, improve stability and reduce hysteresis [30,31]. Pentacene is often used in field-effect transistors (FET) and photodiode because of its high carrier mobility [32,33]. Here, pentacene and PTAA meet the requirements of energy level matching, which can effectively realize rectification [34]. The insert figure is circuit schematic diagram of a single-pixel. The perovskite polycrystalline films are usually fabricated by spin-coating, which is generally divided into one- and two-step processes. For one-step, the antisolvent is dropped during the spin-coating process, which promotes the rapid crystallization and precipitation of precursors. It is also the common method with simple process, while the morphology and orientation of polycrystalline films are difficult to control. Two-step can change the film morphology by controlling the content of PbI2, and it is more easily used in large-area preparation. In this research, perovskite films are prepared by two processes to enumerate their applicability.
Fig. 1. (a) Schematic of pixel unit structure of PD. From bottom to top, ITO/SnO2/Perovskite/PTAA/NaF/Al. (insert: circuit schematic diagram of a single-pixel.) (b) XRD patterns of one- (black line) and two-step (red line) perovskite. (c-d) SEM images of the perovskite films fabricated from one- and two-step. (e-f) SEM images of the PDs fabricated from one- and two-step. The scale bar is 1 µm.
The X-ray diffraction (XRD) patterns [Fig. 1(b)] show good crystallinity of the perovskite films prepared by one- and two-step processes. One-step (black line) shows three obvious characteristic peaks, which are located at 14.17°, 28.49° and 31.89° and corresponding to (110), (220) and (310) planes, respectively. The presence of some other diffraction peaks indicates that the orientation selectivity cannot control by one-step process easily. However, the crystal orientation of two-step (red line) is mainly (110) and (220), that is, the film is mainly tetragonal structure and has good crystal orientation selectivity. Due to the dense PbI2 film, a part of the unreacted PbI2 (12.72°) can better match the energy levels in the conventional structure and further improve the carrier transport efficiency, which is consistent with the results of Yohan Ko et al. [28]. Scanning electron microscopy (SEM) images of the perovskite film surface morphologies fabricated by one- [Fig. 1(c)] and two-step [Fig. 1(d)], respectively, show that the grain sizes of the films prepared by one-step are larger and the morphologies are smoother than two-step, but both of them have tightly grain arrangement and fewer defects. For the two-step process, the high density of the PbI2 film affected the grain growth, leading to the decrease of perovskite grain size. The surface is relatively rough in two-step because perovskite is formed slowly in isopropanol [35]. Figures 1(e), 1(f) show the cross sections of PDs prepared by the one- and two-step processes respectively. The thickness of the film can reach 650 nm by one-step, but there is superposition of vertically distributed grains, which will cause some defects and recombination. The thickness of the two-step is relatively thin, but most of the grains do not appear superimposed.
The photoelectric responses are studied by measuring the current-voltage (I-V) characteristics of the device. As shown in Fig. 2(a), under 532 nm laser irradiation, both one- (blue lines) and two-step (red lines) devices exhibited good rectifying behaviour, which benefited from the rectify diode (the log scale of Fig. 2(a) is shown in Fig. S2). With the increase of light intensity, the current increases significantly, and reach current saturation at bias of −2 V. It should be noted that the photocurrent of the two-step device is higher under the same light intensity, which may be due to fewer defects and more consistent crystal orientation [36]. When a bias voltage of −2 V is applied (which is the operating voltage in the performance research), the spectral responsivity (R) in 300-800 nm is shown in Fig. 2(b), which can be expressed as R=(Iill-Id)/P×A, where Iill is the photocurrent, P is the light power, A is the effective area of the PD (4 mm2) and Id is the dark current. The responsivity of the one [Fig. 2(b)] and two-step [(Fig. 2(c)] devices are all 0.39 A/W at 755 nm. The two devices have similar spectral responsivity. The responsivity of the two-step device is slightly higher than that of the one-step device at different light intensities under 532 nm laser illumination [Fig. 2(d)], but the two devices show similar trends. Due to the addition of chloride ions, the band gap of the two-step device is narrower. The results accord with the absorption of perovskite films (Fig. S3).
Fig. 2. (a) I-V curves of devices under different light intensities at 532 nm illumination. MAPbI3 and MAPbI3-xClx are fabricated by one- and two-step processes, respectively. Spectral responsivity and specific detectivity of (b) one- and (c) two-step devices. (d) Responsivity under different light intensities at 532 nm laser incident. Photocurrent on-off characteristic of the device by (e) one- and (f) two-step at 532 nm illumination under different light intensities. (g) The linear ranges of one- and two-step are measured under different light intensity illumination. The solid line is the fitted curve. Photocurrent rise and decay time of (h) one- and (i) two-step device measured at a bias of −2 V and at a light intensity of 100 µW/cm2 for 532 nm.
Since the noise of the device is dominated by the shot noise under the operating voltage [37], the specific detectivity (D*) of the device can be calculated by the following formula [7,10,38,39]:
where q is elementary charge. D* is calculated to be 4.53×1012 Jones and 4.83×1011 Jones for one- and two-step devices at 755 nm. The two-step device has a smaller D* due to the thinner film resulting in a larger dark current at the same operating voltage.Through the further research of the on-off ratio for one- and two-step devices [Figs. 2(e), 2(f)], in addition to showing good repeatability and stability, the on-off ratio is 1.62×103 under 10.46 mW/cm2 illumination for one-step and 5.07×102 under 10.13 mW/cm2 illumination for two-step. These results indicate that the devices are comparable to other PDs (Table 1). Apart from that, a large linear dynamic range (LDR) is very important for the imaging applications of PDs, which represents the intensity range in which the responsivity keeps constant and is expressed by a formula:
where Imax and Imin are the net photocurrent corresponding to the maximum and minimum light intensities in the linear range, respectively. As shown in Fig. 2(g), the photocurrent increases linearly with increasing the light intensity from about 100 nW/cm2 to 10 mW/cm2, calculating a large LDR of 95 dB and 94 dB for one- and two-step devices. Large LDR may benefit from the good carrier transport characteristics and the lower trap density of the active layer, which is the premise of obtaining good imaging quality at different light intensities.
Table 1. Summary of the performance of PDs.
Response speed is also a key performance parameter in PDs. Especially in imaging applications, it is essential for motion analysis and real-time imaging. 532 nm laser, Chopper and oscilloscope are used for measurement of response time. The rise and decay time are defined as the corresponding time from 10% to 90% of the photocurrent. For one- and two-step device [Figs. 2(h), 2(i)] illuminated by a modulated 532 nm laser at the chopper frequency 1 kHz, the rise (τr) and decay (τd) times are 111 µs, 250 µs and 99 µs, 116 µs, respectively. The slightly faster response of the two-step device may be due to the thinner film and shorter carrier transport path. At the same time, the applied bias will also accelerate the carrier moving speed to the two electrodes. It should be noted that the response speed of device should be faster when the effective area of single pixel is smaller.
The physical mechanism of the on- and off-state of device is explained as follows [ Figs. 3(a), (b)]. Light illuminates from the side of glass and absorbed by perovskite to generate electron-hole pairs. At 0 V bias, due to the low work function of NaF/Al electrode, there is a large barrier between NaF/Al and pentacene, the internal field and large rectifying barrier for the pentacene layer blocks the flow of carriers. There is no response even if under illumination. Therefore, the device is in the off-state at 0 V. However, at – 2 V bias, that is on-state, electrons and holes can be collected by ITO and Al electrode due to the overcoming barrier, respectively.
Fig. 3. Band diagram of the perovskite imaging device at (a) 0 V (off-state) and (b) −2 V (on-state).
Due to the lower work function of the NaF/Al electrode, the device keeps off-state at 0 V. It can not only reduce the crosstalk between pixels, but also reduce the standby power consumption. In order to visually analysis the on-off state, the current-voltage relationships of photodiode (ITO/SnO2/MAPbI3/PTAA/Al), rectify diode (ITO/PTAA/Pentacene/NaF/Al) and PD (ITO/SnO2/MAPbI3/PTAA/Pentacene/NaF/Al) were compared, respectively [Fig. 4(a)]. Firstly, under 100 µW/cm2 light incident, photodiode has normal current response at 0 V, Voc is above 0.5 V, dark current increases with increasing negative bias, and photocurrent is about 2×10−6 A. Secondly, rectify diode has a good rectification effect, and the current in the range of −1 V to 1 V is in the order of 10−10 A, which can effectively reduce the dark current of PD. Finally, under the same illumination conditions, the PD has no light response in the range of 0 V to 1 V, maintains the off-state, and the dark current is two orders of magnitude lower than that of the photodiode under the same bias. At −2 V bias, the photocurrent of PD is about 1.5×10−6 A, which basically meets the light response of photodiode with the same conditions. In addition, there is obvious hysteresis in PD compared with photodiode, which may be caused by carrier recombination caused by interlayer defects or different carrier mobility in each layer.
Fig. 4. (a) Comparison of I-V curves of discrete PD, photodiode and rectify diode measured with a 532 nm laser (100 µW/cm2). Comparison of the on-off characteristics under different light intensity of (b) one-step device and (c) two-step device.
The photocurrent of one- [Fig. 4(b)] and two-step [Fig. 4(c)] devices can be distinguished in the on-state even when the light is weak (Fig. S4), while the off-state can be maintained when the light is strong. The slow response under weak light can be explained by the deep-shallow traps theory [40]. There are fewer photogenerated carriers under weak light illumination, carriers are first captured by deep traps, while the deep traps have a longer charge release time, so the slow process dominates under weak light illumination. The response speed under weak light is shown in Fig. S5, the rise and decay times are 155 ms, 118 ms and 101 ms, 72 ms for one- and two-step device under 105 nW/cm2 light intensity, respectively.
Finally, the application of 8×8 PD array in the multipoint light distribution by applying green light (100 µW/cm2). As shown in Fig. 5(a), a patterned metal shadow mask is added between the light source and the PD. 64 pixels are sequential scanned by grounding the Al electrode and applying −2 V operating voltage to the ITO electrode. The images of one- [Figs. 5(b)–5(d)] and two-step [Figs. 5(e)–5(g)] obtained with letter masks T, J and U, and the images have high contrast and uniformity. It was found that there is a part of crosstalk for the two-step device, which may be caused by the high dark current brought by the thinner perovskite film. For future commercial applications, it is necessary to further improve the resolution, reduce interface defects and optimize the structure.
Fig. 5. (a) Schematic diagram of 8×8 PD array to detect multipoint light distribution. Imaging results of the letters with the (b-d) one- and (e-f) two-step 8×8 PD array under a 530 nm green light illuminated with a light intensity of 100 µW/cm2.
4. Conclusions
In summary, this study demonstrates the application of 8×8 PD array based on one- (MAPbI3) and two-step (MAPbI3-xClx) in light detection and imaging. The device has a wide spectral response range (300-800 nm), and the maximum R and D* can reach 0.39 A/W and 4.53×1012 Jones for one-step process. This monolithic stacked two-terminal structure is simple in wiring and has a high detectability. The device consumes low power, with standby voltage of 0 V and operating voltage of −2 V. In the imaging applications, both processes obtain high image quality. This device has wide potential in light detection and high-resolution imaging.
Funding
Shenzhen Fundamental Research Program (JCYJ20170412154447469); National Natural Science Foundation of China (61675147, 61735010, 91838301); National Key Research and Development Program of China (2017YFA0700202).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Supplemental document
See Supplement 1 for supporting content.
References
1. C. Bao, J. Yang, S. Bai, W. Xu, Z. Yan, Q. Xu, J. Liu, W. Zhang, and F. Gao, “High performance and stable all-inorganic metal halide perovskite-based photodetectors for optical communication applications,” Adv. Mater. 30(38), 1803422 (2018). [CrossRef]
2. C. Choi, M. K. Choi, S. Liu, M. S. Kim, O. K. Park, C. Im, J. Kim, X. Qin, G. J. Lee, K. W. Cho, M. Kim, E. Joh, J. Lee, D. Son, S. H. Kwon, N. L. Jeon, Y. M. Song, N. Lu, and D. H. Kim, “Human eye-inspired soft optoelectronic device using high-density MoS2-graphene curved image sensor array,” Nat. Commun. 8(1), 1664 (2017). [CrossRef]
3. M. Liao, “Progress in semiconductor diamond photodetectors and MEMS sensors,” Functional Diamond 1(1), 29–46 (2021). [CrossRef]
4. R. D. Jansen-van Vuuren, A. Armin, A. K. Pandey, P. L. Burn, and P. Meredith, “Organic photodiodes: the future of full color detection and image sensing,” Adv. Mater. 28(24), 4766–4802 (2016). [CrossRef]
5. D. Baierl, L. Pancheri, M. Schmidt, D. Stoppa, G. F. Dalla Betta, G. Scarpa, and P. Lugli, “A hybrid CMOS-imager with a solution-processable polymer as photoactive layer,” Nat. Commun. 3(1), 1175 (2012). [CrossRef]
6. W. Lee, J. Lee, H. Yun, J. Kim, J. Park, C. Choi, D. C. Kim, H. Seo, H. Lee, J. W. Yu, W. B. Lee, and D. H. Kim, “High-resolution spin-on-patterning of perovskite thin films for a multiplexed image sensor array,” Adv. Mater. 29(40), 1702902 (2017). [CrossRef]
7. Y. Li, Z. Shi, L. Lei, S. Li, D. Yang, D. Wu, T. Xu, Y. Tian, Y. Lu, Y. Wang, L. Zhang, X. Li, Y. Zhang, G. Du, and C. Shan, “Ultrastable lead-free double perovskite photodetectors with imaging capability,” Adv. Mater. Interfaces 6(10), 1900188 (2019). [CrossRef]
8. T. N. Ng, W. S. Wong, M. L. Chabinyc, S. Sambandan, and R. A. Street, “Flexible image sensor array with bulk heterojunction organic photodiode,” Appl. Phys. Lett. 92(21), 213303 (2008). [CrossRef]
9. W. L. Tsai, C. Y. Chen, Y. T. Wen, L. Yang, Y. L. Cheng, and H. W. Lin, “Band tunable microcavity perovskite artificial human photoreceptors,” Adv. Mater. 31, 1900231 (2019). [CrossRef]
10. C. Y. Wu, Z. Wang, L. Liang, T. Gui, W. Zhong, R. C. Du, C. Xie, L. Wang, and L. B. Luo, “Graphene-assisted growth of patterned perovskite films for sensitive light detector and optical image sensor application,” Small 15(19), 1900730 (2019). [CrossRef]
11. W. Wu, X. Wang, X. Han, Z. Yang, G. Gao, Y. Zhang, J. Hu, Y. Tan, A. Pan, and C. Pan, “Flexible photodetector arrays based on patterned CH3NH3PbI3-x-Clx perovskite film for real-time photosensing and imaging,” Adv. Mater. 31(3), 1805913 (2019). [CrossRef]
12. X. Xu, W. Deng, X. Zhang, L. Huang, W. Wang, R. Jia, D. Wu, X. Zhang, J. Jie, and S. T. Lee, “Dual-band, high-performance phototransistors from hybrid perovskite and organic crystal array for secure communication applications,” ACS Nano 13(5), 5910–5919 (2019). [CrossRef]
13. P. Zalar, N. Matsuhisa, T. Suzuki, S. Enomoto, M. Koizumi, T. Yokota, M. Sekino, and T. Someya, “A monolithically processed rectifying pixel for high-resolution organic imagers,” Adv. Electron. Mater. 4(6), 1700601 (2018). [CrossRef]
14. Y. L. Wu, N. Matsuhisa, P. Zalar, K. Fukuda, T. Yokota, and T. Someya, “Low-power monolithically stacked organic photodiode-blocking diode imager by turn-on voltage engineering,” Adv. Electron. Mater. 4(11), 1800311 (2018). [CrossRef]
15. Y. L. Wu, K. Fukuda, T. Yokota, and T. Someya, “A highly responsive organic image sensor based on a two-terminal organic photodetector with photomultiplication,” Adv. Mater. 31(43), 1903687 (2019). [CrossRef]
16. X. Hu, X. Zhang, L. Liang, J. Bao, S. Li, W. Yang, and Y. Xie, “High-performance flexible broadband photodetector based on organolead halide perovskite,” Adv. Funct. Mater. 24(46), 7373–7380 (2014). [CrossRef]
17. G. E. Eperon, K. H. Stone, L. E. Mundt, T. H. Schloemer, S. N. Habisreutinger, S. P. Dunfield, L. T. Schelhas, J. J. Berry, and D. T. Moore, “The role of dimethylammonium in bandgap modulation for stable halide perovskites,” ACS Energy Lett. 5(6), 1856–1864 (2020). [CrossRef]
18. X. Hu, H. Wang, Y. Ying, M. Wang, C. Zhang, Y. Ding, H. Li, W. Li, S. Zhao, and Z. Zang, “Methylammonium chloride as an interface modificator for planar-structure perovskite solar cells with a high open circuit voltage of 1.19 V,” J. Power Sources 480, 229073 (2020). [CrossRef]
19. W. Li, H. Wang, X. Hu, W. Cai, C. Zhang, M. Wang, and Z. Zang, “Sodium benzenesulfonate modified poly (3,4Ethylenedioxythiophene):polystyrene sulfonate with improved wettability and work function for efficient and stable perovskite solar cells,” Sol. RRL 5(1), 2000573 (2021). [CrossRef]
20. X. Liu, M. Wang, F. Wang, T. Xu, Y. Li, X. Peng, H. Wei, Z. Guan, and Z. Zang, “High-performance photodetectors with x-ray responsivity based on interface modified perovskite film,” IEEE Electron Device Lett. 41(7), 1044–1047 (2020). [CrossRef]
21. M. Wang, W. Li, H. Wang, K. Yang, X. Hu, K. Sun, S. Lu, and Z. Zang, “Small molecule modulator at the interface for efficient perovskite solar cells with high short-circuit current density and hysteresis free,” Adv. Electron. Mater. 6(10), 2000604 (2020). [CrossRef]
22. Q. Lin, A. Armin, P. L. Burn, and P. Meredith, “Filterless narrowband visible photodetectors,” Nat. Photonics 9(10), 687–694 (2015). [CrossRef]
23. Y. Fang, Q. Dong, Y. Shao, Y. Yuan, and J. Huang, “Highly narrowband perovskite single-crystal photodetectors enabled by surface-charge recombination,” Nat. Photonics 9(10), 679–686 (2015). [CrossRef]
24. Y. Wu, X. Li, Y. Wei, Y. Gu, and H. Zeng, “Perovskite photodetectors with both visible-infrared dual-mode response and super-narrowband characteristics towards photo-communication encryption application,” Nanoscale 10(1), 359–365 (2018). [CrossRef]
25. J. Li, J. Wang, J. Ma, H. Shen, L. Li, X. Duan, and D. Li, “Self-trapped state enabled filterless narrowband photodetections in 2D layered perovskite single crystals,” Nat. Commun. 10(1), 806 (2019). [CrossRef]
26. F.-X. Liang, J.-Z. Wang, Z.-X. Zhang, Y.-Y. Wang, Y. Gao, and L.-B. Luo, “Broadband, ultrafast, self-driven photodetector based on Cs-doped FAPbI3 perovskite thin film,” Adv. Opt. Mater. 5(22), 1700654 (2017). [CrossRef]
27. P. Gui, J. Li, X. Zheng, H. Wang, F. Yao, X. Hu, Y. Liu, and G. Fang, “Self-driven all-inorganic perovskite microplatelet vertical Schottky junction photodetectors with a tunable spectral response,” J. Mater. Chem. C 8(20), 6804–6812 (2020). [CrossRef]
28. Y. Ko, Y. Kim, C. Lee, Y. Kim, and Y. Jun, “Investigation of hole-transporting poly(triarylamine) on aggregation and charge transport for hysteresisless scalable planar perovskite solar cells,” ACS Appl. Mater. Interfaces 10(14), 11633–11641 (2018). [CrossRef]
29. D. Liu, Y. Wang, H. Xu, H. Zheng, T. Zhang, P. Zhang, F. Wang, J. Wu, Z. Wang, Z. Chen, and S. Li, “SnO2-based perovskite solar cells: configuration design and performance improvement,” Sol. RRL 3(2), 1800292 (2019). [CrossRef]
30. T. Bu, J. Li, F. Zheng, W. Chen, X. Wen, Z. Ku, Y. Peng, J. Zhong, Y. B. Cheng, and F. Huang, “Universal passivation strategy to slot-die printed SnO2 for hysteresis-free efficient flexible perovskite solar module,” Nat. Commun. 9(1), 4609 (2018). [CrossRef]
31. L. Lin, T. W. Jones, J. T. Wang, A. Cook, N. D. Pham, N. W. Duffy, B. Mihaylov, M. Grigore, K. F. Anderson, B. C. Duck, H. Wang, J. Pu, J. Li, B. Chi, and G. J. Wilson, “Strategically constructed bilayer tin (IV) oxide as electron transport layer boosts performance and reduces hysteresis in perovskite solar cells,” Small 16(12), 1901466 (2020). [CrossRef]
32. Y. Peng, R. Ding, Q. Ren, S. Xu, L. Sun, Y. Wang, and F. Lu, “High performance photodiode based on MoS2/pentacene heterojunction,” Appl. Surf. Sci. 459, 179–184 (2018). [CrossRef]
33. J. Lee, “Pentacene-based photodiode with Schottky junction,” Thin Solid Films 451-452, 12–15 (2004). [CrossRef]
34. J. H. Heo and S. H. Im, “CH3NH3PbI3/poly-3-hexylthiophen perovskite mesoscopic solar cells: Performance enhancement by Li-assisted hole conduction,” Phys. Status Solidi RRL 8(10), 816–821 (2014). [CrossRef]
35. Y. H. Lee, J. Luo, R. Humphry-Baker, P. Gao, M. Grätzel, and M. K. Nazeeruddin, “Unraveling the reasons for efficiency loss in perovskite solar cells,” Adv. Funct. Mater. 25(25), 3925–3933 (2015). [CrossRef]
36. Q. Liang, J. Liu, Z. Cheng, Y. Li, L. Chen, R. Zhang, J. Zhang, and Y. Han, “Enhancing the crystallization and optimizing the orientation of perovskite films via controlling nucleation dynamics,” J. Mater. Chem. A 4(1), 223–232 (2016). [CrossRef]
37. C. Xie, C. Mak, X. Tao, and F. Yan, “Photodetectors based on two-dimensional layered materials beyond graphene,” Adv. Funct. Mater. 27(19), 1603886 (2017). [CrossRef]
38. F. Cao, L. Meng, M. Wang, W. Tian, and L. Li, “Gradient energy band driven high-performance self-powered perovskite/CdS photodetector,” Adv. Mater. 31(12), 1806725 (2019). [CrossRef]
39. W. Deng, H. Huang, H. Jin, W. Li, X. Chu, D. Xiong, W. Yan, F. Chun, M. Xie, C. Luo, L. Jin, C. Liu, H. Zhang, W. Deng, and W. Yang, “All-sprayed-processable, large-area, and flexible perovskite/mxene-based photodetector arrays for photocommunication,” Adv. Opt. Mater. 7(6), 1801521 (2019). [CrossRef]
40. F. Guo, B. Yang, Y. Yuan, Z. Xiao, Q. Dong, Y. Bi, and J. Huang, “A nanocomposite ultraviolet photodetector based on interfacial trap-controlled charge injection,” Nat. Nanotechnol. 7(12), 798–802 (2012). [CrossRef]
