Fabrication of HTL free perovskite solar cell using compositional engineering via cesium bromide for ambient fabrication

With advancements in the field of perovskite solar cells (PSCs), the research focus has shifted toward long-term stability and resistance to environmental factors. The MAPbI₃-based perovskite absorber layer (MAI) often faces issues such as phase instability, moisture degradation, poor morphology, and defect-induced recombination losses. To address these challenges, this study explores the advantages of substituting cesium bromide (CsBr) into MAI. CsBr substitution results in a substantial enhancement of the absorber layer by improving film crystallinity and grain size, along with a reduction in grain boundaries, leading to decreased charge recombination. Consequently, light absorption is enhanced, accompanied by a slight increase in the bandgap. Photoluminescence (PL) studies reveal that the most effective charge transport occurs at the interface between the electron transport layer (ETL) and the CsBr-doped MAPbI₃ absorber layer (Cs-MAI). Finally, the champion cell fabricated with Cs-MAI exhibited a photovoltaic conversion efficiency (PCE) of 14.21%, representing a 26.95% improvement compared to its standard counterpart, which showed a PCE of only 10.38%. In addition to improved efficiency, stability testing indicates that the CsBr-based cell demonstrates superior stability, with only a 3.26% drop in PCE over a 30-day period, compared to an 11.80% PCE loss observed in MAI-based cells.