Visualizing\nand Suppressing Nonradiative Losses in\nHigh Open-Circuit Voltage n‑i-p-Type CsPbI3 Perovskite\nSolar Cells

Cesium lead iodide (CsPbI3) has attracted\nincreasing\nattention for its photovoltaic applications, owing to its thermal\nstability and suitable band gap for tandem solar cells. However, the\nsevere nonradiative recombination losses in CsPbI3-based\nperovskite solar cells generally restrict their open-circuit voltage\n(VOC) to the range of 0.9 to 1.1 V. This\nwork uniquely reports a method to visualize all defect-assisted recombination\npathways with photoluminescence (PL) techniques. Visible and valuable\ninsight into the reduction of defect densities on a micrometer scale\nwas obtained by the bottom surface and bulk passivation with barium\nhydroxide and trioctylphosphine oxide. The dual effects successfully\nimprove the VOC of the solar cell from\n0.87 to 1.17 V. These results highlight the potential of hyperspectral\nPL imaging as a powerful tool to give guidance to further suppress\nthe nonradiative VOC losses in all-inorganic\nperovskites.