Understanding the Heterointerfaces in Perovskite Solar Cells via Hole Selective Layer Surface Functionalization

Interfaces in perovskite solar cells (PSCs) play a pivotal role in determining device performance by influencing charge transport and recombination. Understanding the physical processes at these interfaces is essential for achieving high-power conversion efficiency in PSCs. Particularly, the interfaces involving oxide-based transport layers are susceptible to defects like dangling bonds, excess oxygen, or oxygen deficiency. To address this issue, the surface of NiOx is passivated using octadecylphosphonic acid (ODPA), resulting in improved charge transport across the perovskite hole transport layer (HTL) interface. This surface treatment has led to the development of hysteresis-free devices with an impressive approximate to 13% increase in power conversion efficiency. Computational studies have explored the halide perovskite architecture of ODPA-treated HTL/Perovskite, aiming to unlock superior photovoltaic performance. The ODPA surface functionalization has demonstrated enhanced device performance, characterized by superior charge exchange capacity. Moreover, higher band-to-band recombination in photoluminescence and electroluminescence indicates presence of lower mid-gap energy states, thereby increasing the effective photogenerated carrier density. These findings are expected to promote the utilization of various phosphonic acid-based self-assembly monolayers for surface passivation of oxide-based transport layers in perovskite solar cells. Ultimately, this research contributes to the realization of efficient halide PSCs by harnessing the favorable architecture of NiOx interfaces. ODPA self-assembly monolayer (SAM) modifies HTL-Perovskite interface without altering crystallography. It highlights film and device quality improvements through interfacial defect reduction, followed by a detailed analysis of efficiency, stability, and charge carrier dynamics. Increased band-to-band recombination in photoluminescence and electroluminescence indicates enhanced effective photogenerated carrier density, supporting the use of phosphonic acid-based SAMs for surface passivation in perovskite solar cells.image