Nonpolar and Ultra-long-chain Ligand to Modify the Perovskite Interface toward High-Efficiency and Stable Wide Bandgap Perovskite Solar Cells

Though tandem solar cells (TSCs) based on wide-bandgap perovskite solar cells (WB-PSCs) as the top sub-cells continuously gain efficiency breakthroughs, the low power conversion efficiency (PCE) of WB-PSCs caused by the defects and interface energy-level mismatch is still a vital issue limiting their performance. Moreover, the stability of the perovskite layer against the moisture and subsequent fabrication process is essential to highly stable TSCs. Herein, a nonpolar material with an ultra-long chain, didodecyldimethylammonium bromide (DDAB), was introduced to WB-PSCs as an interface material for reducing the surface defects and increasing the surface hydrophobicity of the perovskite layer. The DDAB-modified perovskite surface is much more hydrophobic, with a water contact angle of 104.9°. Systemically experimental studies reveal that apart from the passivation on the point defects, DDAB can suppress the formation of PbI 2 aggregates, smoothing the perovskite surface and shifting the energy level upward. As a result, the 1.74 eV WB-PSCs with inverted structures exhibit a champion PCE of 18.74% by DDAB modification, compared to the standard device with a PCE of 16.50%. The device stability under a relative humidity of >85% is apparently enhanced by 5-fold. This work provides a concept of screening interface materials for highly efficient and stable WB-PSCs.