Influence of Rutile-TiO₂ nanorod arrays on Pb-free (CH₃NH₃)₃Bi₂I₉-based hybrid perovskite solar cells fabricated through two-step sequential solution process

Abstract

The organic-inorganic perovskite compound (CH₃NH₃)₃Bi₂I₉ (MBI) has lower toxicity and higher stability than lead-based perovskite. In this work, we fabricated MBI perovskite-based solar cells (PSCs) through a two-step sequential-solution process by using rutile TiO₂ nanorod array (NRA) films as the electron transporting layer (ETL) for the first time. The thickness, roughness, and crystal structure of the rutile TiO2 NRAs prepared by hydrothermal method with different reaction times were thoroughly characterized and correlated with the photovoltaic performance of PSCs. Results of morphological and structural analyses, as well as time-resolved photoluminescence studies, indicated the effect of TiO₂ NRA film thickness on the carrier recombination and photovoltaic performance of MBI-based PSCs. The MBI-based device was also stable in an environment with >50% humidity for more than 67 days