Abstract

Despite that organic-inorganic lead halide perovskites have attracted enormous scientific attention for energy conversion applications over the recent years, the influence of temperature and the type of the employed hole transport layer (HTL) on the charge carrier dynamics and recombination processes in perovskite photovoltaic devices is still largely unexplored. In particular, significant knowledge is missing on how these crucial parameters for radiative and non-radiative recombinations, as well as for efficient charge extraction vary among different perovskite crystalline phases that are induced by temperature variation.

Herein, we perform micro photoluminescence (μPL) and ultrafast time resolved transient absorption spectroscopy (TAS) in Glass/Perovskite and two different Glass/ITO/HTL/Perovskite configurations at temperatures below room temperature, in order to probe the charge carrier dynamics of different perovskite crystalline phases, while considering also the effect of the employed HTL polymer. Namely, CH₃NH₃PbI₃ films were deposited on Glass, PEDOT:PSS and PTAA polymers, and the developed Glass/CH₃NH₃PbI₃ and Glass/ITO/HTL/CH₃NH₃PbI₃ architectures were studied from 85 K up to 215 K in order to explore the charge extraction dynamics of the CH₃NH₃PbI₃ orthorhombic and tetragonal crystalline phases.

It is observed an unusual blueshift of the bandgap with temperature and the dual emission at temperature below of 100 K and also, that the charge carrier dynamics, as expressed by hole injection times and free carrier recombination rates, are strongly depended on the actual pervoskite crystal phase, as well as, from the selected hole transport material.