Interfacial Treatment by 1,4-Phenyldiammonium Diiodide to Significantly Improve the Performance of Carbon-Based CsPbI₂Br Solar Cells

Herein, a facile treatment to the interface of the CsPbI2Br layer and the carbon electrode using 1,4-phenyldiammonium diiodide (PhDADI) is reported for significantly improving the power conversion efficiency (PCE) of the corresponding CsPbI2Br solar cells based on a carbon electrode without a hole transport material. Owing to the positive contribution of the PhDADI treatment including the reduced defect density, improved crystallinity, and decreased surface roughness of CsPbI2Br, all key device parameters such as the open-circuit voltage, short-circuit current density, and fill factor are improved, thus leading to the PCE promotion from 11.80% for the control device without the PhDADI modification to 14.20%. Moreover, the stability test indicates that the PhDADI-modified device has the superior stability to the control device without PhDADI.