Hybrid organic-inorganic perovskites have attracted intensive interest as active materials for high-performance photodetectors. However, studies on the electron transport layer (ETL) and its influence on the response time of photodetectors remain limited. Herein, we compare the performances of perovskite photodetectors with TiO2 and SnO2 ETLs, especially on the response time. Both photodetectors exhibit a high on/off current ratio of 105, a large detectivity around 1012 Jones, and a linear dynamic range over 80 dB. The SnO2-based perovskite photodiodes show ultrahigh response rates of 3 and 6 μs for the rise and decay times, respectively. However, photodetectors with TiO2 ETLs have low responsivity and long response time at low driving voltage, which is attributed to the electron extraction barrier at the TiO2/perovskite interface and the charge traps in the TiO2 layer. Furthermore, the dark current of SnO2-based perovskite photodiodes is effectively suppressed by inserting a poly(vinylpyrrolidone) interlayer, and then the on/off current ratio increases to 1.2 × 106, corresponding to an improvement of 1 order of magnitude. Such low-cost, solution-processable perovskite photodetectors with high performance show promising potential for future optoelectronic applications.
Keywords: dark current; electron transport layer; perovskite; photodetectors; response time.