Effect of Hole Transport Layer in Planar Inverted Perovskite Solar Cells

Abstract

This study compares the photovoltaic performance of the inverted planar perovskite solar cells with and without poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) as the hole transport layer (HTL). The device ITO/CH3NH3PbI3/PCBM/Al (PCBM: [6,6]-phenyl-C61-butyric acid methyl ester) without PEDOT:PSS achieved a power conversion efficiency of 5.69%, which is much lower than that (ca. 10%) for the device with HTL. The effect of the HTL on the device performance was investigated by electronic impedance spectroscopy and transient photovoltage decay characterization. The results revealed that the low efficiency of HTL-free devices can be attributed to an inefficient electron-blocking capability. The absence of the HTL causes serious recombination at the ITO/perovskite interface, and thus results in low photovoltage and fill factor.