Surface Regulation via Carboxylate Polymer for Efficient and Stable CsPbIBr Perovskite Solar Cells.

CsPbIBr perovskite solar cell (PSC) is a promising candidate for high-efficiency single-junction and tandem solar cells. However, due to the numerous surface defects of the CsPbIBr film and the mismatch of energy levels at the CsPbIBr/charge transport layer interface, the power conversion efficiency (PCE) of CsPbIBr PSC is still significantly lower than the theoretical limits. To alleviate those issues, in this work, a carboxylate-based p-type polymer, TTC-Cl, is employed to modify the surface of CsPbIBr layer. TTC-Cl can interact with uncoordinated Pb, thereby mitigating surficial defects of CsPbIBr film and reducing non-radiative recombination losses. Furthermore, TTC-Cl also improves the band properties of the CsPbIBr thin film surface, rendering it more p-type, which facilitates hole transport. Consequently, the CsPbIBr PSCs with TTC-Cl modification achieve a remarkable PCE of 17.81%, which is notably higher than that of counterpart without TTC-Cl (15.87%). Moreover, CsPbIBr PSCs with TTC-Cl modification also exhibit better stability. This work highlights the importance of surface regulation via carboxylate polymer for further enhancing the performance of CsPbIBr PSCs.