Meihua Shou

Bio: Meihua Shou is an academic researcher from South China University of Technology. The author has contributed to research in topics: Dark current & Photodetector. The author has an hindex of 3, co-authored 8 publications receiving 28 citations.

Lateral Polymer Photodetectors Using Silver Nanoparticles Promoted PffBT4T-2OD:PC61BM Composite

Abstract: The fabrication of lateral polymer photodetectors (L-PPDs) is rarely reported in literature. Unlike vertical photodiode or phototransistor, it would be much more difficult to experimentally improve all of the performance metrics in lateral structure under long channel without compromising any of them. The performance metrics include charge separation, photomultiplication, trapped-charge relaxation, dark current, fast response and so on. In this research, L-PPDs with comparable performance to photodiodes were developed, and the photodetectors have the structure of quartz/Ag-NPs (1 nm)/ PMMA (30 nm)/PffBT4T-2OD:PC61BM (D/A ratio = 1:1.2; 140 nm)/Ag–Ag electrodes. A phase control of BHJ allows effective electrons to be trapped under high PCBM ratio, which simultaneously gives high charge separation and photomultiplication (gain = 161.5 at a current density of 73 mA/cm2). Moreover, photogenerated electrons trapped in active layer can be neutralized by photoinduced holes stored in Ag-NPs, resulting in an obvio...

Ultrahigh photosensitive organic phototransistors by photoelectric dual control

Abstract: Organic phototransistors (OPTs) simultaneously introduce photo-induced holes and electrons into the structure of organic field-effect transistors (OFETs). The memory effect of the minority carrier is the origin of the large dark current and slow response during the light on/off switching, which is detrimental to the OPT performance and cycling stability. In this research, we report a novel OPT working mode by photoelectric dual control. After each light switch, the dark current is erased by the gate voltage in depletion mode which remains unchanged during light off; the photocurrent increases by device converting to accumulation mode when the light is on. In this way, high performance OPTs have been obtained in an FBT-Th4(1,4) : PC61BM (5 : 1) composite film with the structure of Si/SiO2/OTS/FBT-Th4(1,4) : PC61BM/Au electrodes, which shows a broad spectral response (maximum values at zero gate bias: R 1.2 × 105 A W−1, gain 3.7 × 105 and D* 3.18 × 1016 Jones) from 410 to 740 nm (calculated from the transfer curve). The best performance with photoelectric dual control under 0.0031 mW cm−2@405 nm is achieved with an on/off current ratio of 1.0 × 106, response 1.6 × 104 A W−1, gain 5.0 × 104, spectral detectivity 2.3 × 1017 Jones and response time sub-40 ms, which makes the phototransistor a very promising component for light sensing applications.

Simultaneous Photomultiplication Improvement and Response Acceleration for High-Performance Lateral Polymer Photodetectors Based on Bulk Heterojunction.

Abstract: In organic photodetectors, photomultiplication is mainly originated from interfacial and/or bulk charge traps, which induces slow response due to the slow release of trapped charges and strongly limits the optimization of the overall performance. This study has exhibited a remarkable case that the gain (>1) and response speed of the lateral photodetectors are promoted simultaneously and effectively by increasing the trap ratio. For lateral photodetectors with silver nanoparticles and PDPPBTT:PC61BM bulk heterojunction, the gain increases from 12.7 to 19.8 and the fall time decreases from 313.4 to 172.9 ms as the PC61BM ratio increases from 5:1 to 1:1. The lateral photodetector structure with a long electrode distance has been testified to play the key role for simultaneous promotion compared with vertical photodiodes, allowing the charges to trap well in the PC61BM-rich phase at a high PC61BM ratio and accumulation of multiple built-in electric fields. The long channel distance and silver nanoparticles also effectively restrain the increment of dark current with PC61BM loading, resulting in a high detectivity of 1.7 × 1012 Jones under 0.031 mW cm-2 @ 820 nm. It is of great theoretical and practical value for the high-performance photodetectors with simultaneous high photomultiplication and quick response.

Photo-switchable electron-transporting layers for self-driven perovskite photodetectors towards high detectivity

Abstract: Vertical-structure photodetectors usually have the advantages of fast response speed and low driving voltage, but suffer from the high dark current that suppresses the detectivity of the devices. Introducing hole/electron-transporting or blocking layers has thus been widely considered to reduce the dark current, but may simultaneously cause the undesirable loss of photocurrent. Herein, we apply photo-switchable electron-transporting layers into vertical-structure photodetectors, which effectively reduces the dark current without sacrificing photocurrent for achieving the high detectivity. Organic dye molecules, perylene bisimides (PBI-H), are doped into the matrix of zinc oxide (ZnO) to achieve the photo-switchable layer (ZnO:PBI-H), which is less conductive in the dark for the inserted low-conductivity organic molecules but highly conductive under light irradiation due to the photo-induced electron transfer from PBI-H to ZnO. Perovskite is used as the photoactive layer in the photodetectors, and a thin layer of polyethylenimine ethoxylated (PEIE) is inserted between the ZnO:PBI-H layer and the perovskite layer in order to inhibit the decomposition of perovskite caused by ZnO. The optimized photodetector based on a ZnO:PBI-H electron-transporting layer shows the highest detectivity up to 2.5 × 1013 cm Hz1/2 W−1 (Jones) at zero bias (light intensity of 126 μW cm−2), which is more than doubled when compared with the device based on ZnO. In addition, the photoresponse stability of the device is also improved by the photo-switchable layer. The primary result sheds new light on the great potential of photo-switchable materials for the development of high-performance photodetectors.

Recent Progress in Organic Photodetectors and their Applications.

Abstract: Organic photodetectors (OPDs) have attracted continuous attention due to their outstanding advantages, such as tunability of detecting wavelength, low-cost manufacturing, compatibility with lightweight and flexible devices, as well as ease of processing. Enormous efforts on performance improvement and application of OPDs have been devoted in the past decades. In this Review, recent advances in device architectures and operation mechanisms of phototransistor, photoconductor, and photodiode based OPDs are reviewed with a focus on the strategies aiming at performance improvement. The application of OPDs in spectrally selective detection, wearable devices, and integrated optoelectronics are also discussed. Furthermore, some future prospects on the research challenges and new opportunities of OPDs are covered.

Highly-sensitive broadband photomultiplication type all-polymer photodetectors and the applications in optical pulse counting

Abstract: Broadband photomultiplication type all-polymer photodetectors (PM-APDs) are achieved on the basis of ITO/PFN-Br/PBDB-T:PYF-T-o (3:100, wt/wt)/LiF/Au as the configuration. Amounts of isolated hole traps are formed with PBDB-T encircled by PYF-T-o...

Ultrahigh photosensitive organic phototransistors by photoelectric dual control

Abstract: Organic phototransistors (OPTs) simultaneously introduce photo-induced holes and electrons into the structure of organic field-effect transistors (OFETs). The memory effect of the minority carrier is the origin of the large dark current and slow response during the light on/off switching, which is detrimental to the OPT performance and cycling stability. In this research, we report a novel OPT working mode by photoelectric dual control. After each light switch, the dark current is erased by the gate voltage in depletion mode which remains unchanged during light off; the photocurrent increases by device converting to accumulation mode when the light is on. In this way, high performance OPTs have been obtained in an FBT-Th4(1,4) : PC61BM (5 : 1) composite film with the structure of Si/SiO2/OTS/FBT-Th4(1,4) : PC61BM/Au electrodes, which shows a broad spectral response (maximum values at zero gate bias: R 1.2 × 105 A W−1, gain 3.7 × 105 and D* 3.18 × 1016 Jones) from 410 to 740 nm (calculated from the transfer curve). The best performance with photoelectric dual control under 0.0031 mW cm−2@405 nm is achieved with an on/off current ratio of 1.0 × 106, response 1.6 × 104 A W−1, gain 5.0 × 104, spectral detectivity 2.3 × 1017 Jones and response time sub-40 ms, which makes the phototransistor a very promising component for light sensing applications.