Functional 1,3‐DTu Additive in Perovskite Layer for Stable Triple‐Cation Perovskite Solar Cells with Efficiency Exceeding 23%

Perovskite solar cells (PSCs) have demonstrated immense potential for commercial applications. However, among the factors hindering further improvements in their performance, defects in the perovskite layers during the solution preparation process remain the primary culprit. Here, for the first time, 1,3‐dimethylthiourea (1,3‐DTu) into triple‐cation perovskite layer is introduced, taking advantage of the strong interaction between C=S in 1,3‐DTu and Pb in perovskite to significantly improve the quality of the perovskite thin films. This leads to a notable reduction in defects, suppression of nonradiative recombination, and enhancement of the optoelectronic properties of the films. The outcome proves highly positive, with the optimal PSC demonstrating an impressive power conversion efficiency (PCE) exceeding 23%, which is remarkably higher than the control one that yields ≈21%. Additionally, the optimized device exhibits excellent stability, maintaining over 90% and 83% of its initial PCE after 1200 h aging in air with a ≈30% relative humidity at room temperature and after 1700 h of heating at a constant temperature of 85 °C in N 2 , respectively, much better than the control one without the incorporation of 1,3‐DTu.