Exploring Band Alignment in Dual Cation Perovskite Solar Cells Utilizing Poly(3-hexylthiophene) as the Hole Transport Layer.

Perovskite solar cell (PSC) materials have emerged as a highly promising class of photovoltaics, showcasing exceptional power conversion efficiencies (PCEs) and outstanding light absorption capabilities. These materials hold significant potential to transform solar energy technology, thanks to their tunable bandgaps and effective charge transport mechanisms. A typical PSC device is structured in a layered format, comprising a front contact, electron transport layer (ETL), perovskite absorber, hole transport layer (HTL), and back contact. Each layer plays a vital role in light absorption, charge generation, and transport. The precise alignment of energy bands across these layers is crucial for maximizing efficiency and ensuring the overall stability of the device. By optimizing the materials and structures of each layer, researchers are working to enhance both the performance and longevity of PSCs. This work specifically examines the band alignment of dual cation lead-free PSCs with the general formula AA'BX₃ (where A/A' represents monovalent organic cations, B represents divalent metal cations, and X represents halide anions), in conjunction with poly(3-hexylthiophene) (P3HT) polymers as HTL. Utilizing density functional theory (DFT), we calculated the conduction band minimum (CBM) and valence band maximum (VBM) of the P3HT-based HTLs and dual cation perovskite layers, which is essential for optimizing charge transport and minimizing recombination in PSCs. Our research highlights the significance of proper band alignment as a key factor in optimizing solar cell efficiency and lays the groundwork for future studies addressing other critical parameters, including layer thickness, doping levels, temperature effects, and the characteristics of adjacent layers, thereby contributing to the ongoing advancement of perovskite solar cell technology.