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.