TWO-DIMENSIONAL ELECTRONIC SPECTROSCOPY AND TRANSIENT ABSORPTION STUDIES OF ULTRAFAST DYNAMICS IN PEROVSKITE THIN FILMS AND BORONDIPYRROMETHENE DYES

Abstract

The absorption of sunlight by a semiconductor initiates a series of dynamical processes that occuron a vast timescale ranging from the femtosecond (10^-15 s) to the nano (10^-9 s) or microsecond (10^-6 s). How effectively light is converted into electrical current is directly determined by these dynamical phenomena. Therefore, in order to design efficient solar cells, knowledge of the relaxation dynamics of the photogenerated species is highly critical. Lead halide perovskites are currently in the limelight not only because of their remarkably rapid improvement of the power conversion efficiency but also because the photogenerated charges retain their excess energy for an unusually long time. This so-called slow hot-carrier cooling opens the door for further enhancement of the power conversion efficiency of perovskite solar cells. Nevertheless, hot-carrier cooling takes place simultaneously with other many-body phenomena. The interplay among them is still beyond our grasp, manifested by the inconsistencies in the understanding of the initial carrier relaxation picture. This thesis thus explores the capability of advanced laser pulses and spectroscopic techniques to tackle questions in the ultrafast dynamics of perovskites, contributing to the resolution of inconsistencies and to a better comprehension of the photodynamics of perovskites.