Study on photo-induced carrier dynamics of methylammonium lead trihalide perovskite solar cell using untrafast transient absorption spectroscopy

Abstract

Methylammonium lead halide perovskite solar cells have been extensively studied as a promising photovoltaics due to their extraordinary advantages; low cost, high absorption of the visible light, small binding energy of exciton, and flexibility. According to the recent study of these materials, the power conversion efficiency (PCE) of perovskite solar cells has increased from 3.8% in 2009 to over 20% in 2016. This high PCE of perovskite solar cells is attributed to their own outstanding photo-physical properties; the long lifetime and diffusion length of photo-excited carriers and remarkable carrier transport performance. These are characterized by the time scales of charge carrier dynamics assessed using ultrafast spectroscopic measurements. In this study, ultrafast time-resolved transient absorption (TA) spectroscopy was employed to report a comparative study on the photo-induced carrier generation and decay dynamics of CH3NH3PbI3 methylammonium lead halide perovskite solar cell devices. The comparative study was carried out with differently modified perovskite solar cell devices at various pump intensities for excitation. The perovskite solar cells devices of varied modification have different properties (ex. surface morphology) and these properties could change the photo-induced charge carrier dynamics. The outstanding characteristics of CH3NH3PbI3 perovskite solar cells as a promising photovoltaics could be explained by the parameters of the photo-induced charge carrier dynamics assessed from these ultrafast spectroscopic measurement series. The experiment was performed with a femtosecond Ti:sapphire laser amplifier system (36 fs pulses centered at 805 nm, 1 kHz repetition rate). Frequency-doubled and supercontinuum lights were used as pump and probe beams, respectively. The polarization angle between pump and probe was adjusted to the magic-angle (54.7°). Comparative results of the conversion performance and photo-induced carrier dynamics of fabricated perovskite solar cells will be explained in the presentation.