Enhancement of Interfacial Properties by Indoloquinoxaline‐Based Small Molecules for Highly Efficient Wide‐Bandgap Perovskite Solar Cells

Abstract Interfacial engineering in organic–inorganic hybrid perovskite solar cells (PSCs) has attracted significant attention, aiming to achieve high‐performing and highly stable devices. Here, newly designed organic small molecules based on quinoxaline and triphenylamine for inverted type wide‐bandgap PSCs are introduced, with the objective of enhancing the interfacial properties between perovskite and NiO_x hole transport layer (HTL). The incorporation of an organic interlayer effectively reduces the energy level offset between the HTL and wide‐bandgap perovskite, while passivating defects within the perovskite layer. It leads to improved charge extraction and minimized non‐radiative recombination at the interface. Furthermore, the enhanced interfacial characteristics and hydrophobicity contribute to the improvement of perovskite film quality, resulting in larger grain size and higher crystallinity. As a result, the power conversion efficiency (PCE) of the PSC is enhanced from 18.9% to 20.1% with the incorporation of the IQTPAFlu interlayer, accompanied by an increase in V_oc to ≈1.3 V, achieving a significantly low V_oc deficit of 0.46 V. And the IQTPAFlu‐based devices demonstrate stable and consistent performance over 500 h, with ≈91% of their initial PCE retained. The highly stable wide‐bandgap PSCs, characterized by high V_oc and PCEs, hold great promise as potential candidates for tandem solar cells.