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

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 NiOx 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 Voc to approximate to 1.3 V, achieving a significantly low Voc deficit of 0.46 V. And the IQTPAFlu-based devices demonstrate stable and consistent performance over 500 h, with approximate to 91% of their initial PCE retained. The highly stable wide-bandgap PSCs, characterized by high Voc and PCEs, hold great promise as potential candidates for tandem solar cells. Quinoxaline and triphenylamine-based organic small molecules are designed to enhance the interfacial properties between the perovskite and the NiOx hole transport layer in inverted-type wide-bandgap perovskite solar cells (PSCs). The integration of these organic interlayers effectively mitigates the energy level offset, passivates defects, and enhances the quality of the perovskite film. This improvement results in an outstanding efficiency of 20.1% for a 1.75 eV wide-bandgap PSC.image