Targeted Regulation of Multifunctional Molecules at Dual Interfaces: Suppressing Phase Separation and Enhancing the...

Wide bandgap (WBG) perovskite plays an irreplaceable and critical role in tandem solar cells. However, the phase separation caused by excessively high halide content seriously restricts the performance and stability of the device. In this work, multifunctional regulation of the device was achieved by introducing 2,7-Dihydroxy-9-fluoronone (DHF) into both the top and bottom interfaces of the WBG perovskite. DHF achieved targeted passivation of the ionic defects in perovskite. In addition, the dual-interface energy level regulation not only enhanced hole extraction, but also enabled the conductivity type of perovskite to complete the transition from n-type to n⁺-type, thereby promoting electron transfer. Meanwhile, experiments showed that I^- was more likely to migrate to the top interface with more defect sites, leading to phase separation, and DHF could effectively suppress phase separation. Density functional theory (DFT) indicated that the migration potential barrier for I^- escaping from the surface of perovskite increases from 0.14 to 1.28 eV. Finally, the device based on DHF dual interface modification achieved a photoelectric conversion efficiency (PCE) of 22.40%, maintaining 83% of the initial PCE after 1000 h of AM 1.5 tracking and 88% of the initial PCE during 1000 h of air stability.