Study On Photodetector Based On Single Crystal Organic-inorganic Hybrid Perovskite CH₃NH₃PbI₃

Nowadays,photodetectors have been widely used in both academic and industrial domains.They have attracted more and more attention from people.Organic-inorganic hybrid perovskites are new materials for the active layer of photodetectors,providing the possibility to develop higher performance photodetectors.At present,most of the perovskite photodetectors are based on polycrystalline films.The presence of a large number of grain boundaries and defects in polycrystalline films limits the optoelectronic properties of the devices.Compared to polycrystal,the single crystal of perovskites has lower defect density,longer carrier diffusion length,and wider spectral absorption,which can further improve the performance of perovskite-based photodetectors.In this paper,we successfully synthesized single crystal organic-inorganic hybrid perovskite CH₃NH₃PbI₃ by inverse temperature crystallization method,and we fabricated a variety of photodetectors based on it.The effect of the electrode material on the properties of photodetector was investigated by evaporating metals with different work functions.The results of experiments showed that the gold electrode can effectively suppress the dark current of photodetector,while the device with silver as the electrode has large dark current and photocurrent,and its responsivity is the highest among the three kinds of devices.In order to find the most suitable test method for perovskite photodetectors,the hysteresis effect is quantified,and the hysteric index of the photodetector with gold electrode under various measurement conditions is studied.We have summarized a series of measures to alleviate the hysteresis phenomenon.We have studied the photodetectors based on single crystal CH₃NH₃PbI₃ from both broadening the response spectrum and improving responsivity.By adding gold nanoparticle modification layer on the surface of single crystal CH₃NH₃PbI₃,the responsivity of the device is nearly three times improved under the near-infrared illumination with a wavelength of 980 nm.On the other hand,a planar heterojunction formed by C₆₀ and CH₃NH₃PbI₃ and a hybrid planar-bulk heterojunction formed by C₆₀:CuPc and CH₃NH₃PbI₃ are introduced into the photodetectors respectively,which greatly improves the photo-to-dark current ratio and responsivity of the devices.