Interfacial modification of wide-bandgap perovskite solar cell approaching 20% with organic hole transport material

The interface modification of perovskite and charge transport is a key factor in improving the efficiency and stability of halide perovskite solar cells (PSCs). In particular, the characteristics of hole transport material (HTM) are crucial in inverted p-i-n structured devices, as they influence the perovskite crystallization and hole carrier extraction and transport. While NiOx is recognized as an efficient HTM due to its low cost, proper band gap, electrical conductivity, and high chemical stability, it has limitations such as rough morphology, poor surface quality, and low intrinsic conductivity. In this study, newly designed organic materials based on quinoxaline and triphenylamine that enhance the interfacial properties between NiOx and perovskite through passivation effect, reducing interface defect sites, are introduced to a wide-bandgap perovskite solar cell. We further confirm that the energy level alignment of these HTMs with the perovskite, along with their dipole moment, play a crucial role in enhancing the built-in potential of PSCs. Additionally, the hydrophobic characteristics of the HTMs improve the crystallinity of the perovskite layer. As a result, the performance and stability of the PSCs incorporating these HTMs are significantly enhanced, approaching high power conversion efficiency of 20%.