Improved Charge Carrier Dynamics of CH₃NH₃PbI₃ Perovskite Films Synthesized by Means of Laser-Assisted Crystallization

Abstract

Although it has been recently demonstrated that the laser-assisted (LA) crystallization process leads to the formation of perovskite absorber films of superior photovoltaic performance compared to conventional thermal annealing (TA), the physical origin behind this important discovery is missing. In this study, CH3NH3PbI3 perovskite thin films have been synthesized by means of LA and TA crystallization on the surface of two hole transport layers (HTLs) namely poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) and poly(triarylamine) (PTAA). A systematic study of the effect of laser irradiation conditions on the crystalline quality and morphology of the perovskite films was performed via scanning electron microscopy, X-ray diffraction, and absorption spectroscopy. Meanwhile, time-resolved transient absorption spectroscopy under inert atmosphere conditions was used to evaluate the carrier transport dynamics. It is found that for the PEDOT:PSS/CH3NH3PbI3 structures, the LA process resulted in perovskite layers of larger grains, faster charge carrier extraction properties, and slower bimolecular recombination, when compared to TA. On the contrary, the LA-assisted formation of the PTAA/CH3NH3PbI3 heterostructures leads to the extensive presence of residual PbI2 and thus inferior performance and charge carrier dynamics.