The highest gain of single-crystalline perovskite photodetectors based on high-quality single-crystalline thin film

Abstract The best performing modern optoelectronic devices rely on single‐crystalline thin‐film (SC‐TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low‐cost solution‐based methods, have achieved substantial success in various optoelectronic devices including solar cells, lasers, light‐emitting diodes, and photodetectors. However, to date, the performance of these perovskite devices based on polycrystalline thin‐film active layers lags behind the epitaxially grown semiconductor devices. Here, a photodetector based on SC‐TF perovskite active layer is reported with a record performance of a 50 million gain, 70 GHz gain‐bandwidth product, and a 100‐photon level detection limit at 180 Hz modulation bandwidth, which as far as we know are the highest values among all the reported perovskite photodetectors. The superior performance of the device originates from replacing polycrystalline thin film by a thickness‐optimized SC‐TF with much higher mobility and longer recombination time. The results indicate that high‐performance perovskite devices based on SC‐TF may become competitive in modern optoelectronics. Summary: In summary, we report that a photodetector based on perovskite SC‐TF can have superior performance than its polycrystalline counterpart. By simultaneously optimizing the perovskites thickness and crystallinity, the device achieves a record photoconductive gain of 50 million and a gain‐bandwidth product of 70 GHz. The superior performance of SC‐TF perovskite photodetectors has also been exemplified by their ultrahigh sensitivity with record detection limit down to 100‐photon level. Further, we systematically study the thickness‐dependent performance of photodetectors. We find that a suitable thickness of the perovskite SC‐TF is crucial in device performance. With the SC‐TF thickness decreasing from about 10 µm to hundreds of nanometers, the lowest detectable power and internal gain improve two and four orders of magnitude, respectively. Our results show that perovskite devices based on SC‐TF have a bright future for optoelectronics. DOI: https://doi.org/10.1002/adma.201704333; Yang Z, Deng Y, Zhang X, et al. High‐Performance Single‐Crystalline Perovskite Thin‐Film Photodetector[J]. Advanced Materials, 2018, 30(8): 1704333.