Energy‐Level Engineering with Co‐Sensitization of Organic Molecules on NiO x for Sn‐Based Perovskite Solar Cells
Ezhumalai Yamuna, Parameswaran Rajamanickam, Kai‐Wei Yu, Yun‐Sheng Shih, Yu Qi Li, Wen‐Yu Chen, Shaohuan Hong, Cheng‐Liang Liu, Xianyuan Jiang, Ming‐Chou Chen, Eric Wei‐Guang DiauABSTRACT
A cooperative self‐assembly of organic small molecules made of diester/diacid‐bithiophene units [BT 2D ‐CE ( 1 ), BT 2D ‐CA ( 2 )] with hexylpyridine‐ or phosphonic acid‐functionalized dithienopyrrole units [DTP 2D ‐Py ( 3 ), DTP 2D ‐PA ( 4 )] was induced atop Nickel Oxide (NiO x ) hole‐transport‐layer for lead‐free tin‐based perovskite solar cells. The pyridine functionality of DTP 2D ‐Py ( 3 ) in conjunction with the carboxyl group of BT 2D ‐CA ( 2 ) altered the NiO x /Perovskite interfacial energetics and accelerates selective hole extraction by passivating the buried interfacial defects, resulting in a power conversion efficiency of 8.1% due to enhanced photovoltage (0.560 to 0.593 V), alongside remarkable operational stability. The crucial role of synergistic energy‐level modulation, especially the Fermi level, was unraveled using ultraviolet photoelectron spectroscopy, demonstrating that combining complementary conjugated organic backbones with targeted functionalities offers versatility for enhancement of overall device performance and stability.