Enhancing the Performance of Perovskite Solar Cells through Cesium Halide Doping

Perovskite films fabricated by a two-step method have the potential to produce high-performance perovskite solar cells (PSCs). The morphology and quality of the inorganic film in the first step play pivotal roles in depositing high-performance PSCs. In this work, cesium halides (CsX) were incorporated into the lead iodide (PbI2) precursor solution to investigate their influence on the crystal structure and photoelectric properties of FA-based PSCs. The introduction of CsX (X = Cl, Br, I) resulted in an increase in the surface roughness of PbI2, thereby facilitating the subsequent reaction with the organic components. Moreover, the incorporation of CsX led to a reduction in defects within the perovskite films, as confirmed by photoluminescence, longitudinal conductivity tests, and light-intensity-dependent open-circuit voltage (VOC) tests. Among the CsX additives, CsCl demonstrated the most pronounced enhancement in device performance, followed by CsBr, and then CsI. Notably, the addition of CsX significantly improved device stability, with the power conversion efficiency (PCE) maintained at more than 85% of its initial value even after 34 days of stability testing, compared to control devices which retained only 65% after 16 days of storage. Furthermore, PSCs modified with CsCl and passivated with phenyl ethylammonium iodide (PEAI) achieved a PCE of 22.47% along with a VOC of 1.1736 V. This work provides a guiding significance for the preparation of high-efficiency PSCs by a two-step method.