Visualizing and Suppressing Nonradiative Losses in High Open-Circuit Voltage n‑i-p-Type CsPbI3 Perovskite Solar Cells

Cesium lead iodide (CsPbI₃) has attracted increasing attention for its photovoltaic applications, owing to its thermal stability and suitable band gap for tandem solar cells. However, the severe nonradiative recombination losses in CsPbI₃-based perovskite solar cells generally restrict their open-circuit voltage (V_OC) to the range of 0.9 to 1.1 V. This work uniquely reports a method to visualize all defect-assisted recombination pathways with photoluminescence (PL) techniques. Visible and valuable insight into the reduction of defect densities on a micrometer scale was obtained by the bottom surface and bulk passivation with barium hydroxide and trioctylphosphine oxide. The dual effects successfully improve the V_OC of the solar cell from 0.87 to 1.17 V. These results highlight the potential of hyperspectral PL imaging as a powerful tool to give guidance to further suppress the nonradiative V_OC losses in all-inorganic perovskites.