Defect Passivation and Enhanced Hole Extraction in Inverted Perovskite Solar Cells via CeO2@MoS2 Interfacial Engineering.

Nanomaterial-based hole transport layers (HTLs) play a vital role in regulating interfacial charge extraction and recombination in perovskite solar cells (PSCs). To improve PSC efficiency, hydrothermally synthesized CeO2@MoS2 nanocomposites (CM NCs) were incorporated as an interfacial buffer layer into a NiOX/MeO-2PACz HTL. The introduction of CM NCs induces strong interfacial interactions, where Mo sites in MoS2 interact with NiOX, modulating the Ni2+/Ni3+ ratio and reducing the interfacial trap density. Moreover, CeO2 promotes the formation of oxygen vacancies, collectively improving the conductivity and hole transport capability of the NiOX HTL. The MoS2-grafted CeO2 interlayer effectively tailors the interfacial energetics and creates an effective channel for hole transfer, thereby reducing open-circuit voltage (VOC) loss and enhancing device performance. This interface modification efficiently enhances hole extraction, and non-radiative recombination is effectively suppressed at the NiOX/MeO-2PACz/perovskite interface. Thereby, incorporating 2 vol% CM NCs into PSCs achieved a power conversion efficiency (PCE) of 17.93%, compared to 17.50% for a 1 vol% CM NCs-based device and 17.01% for the unmodified control device. The enhanced performance at the optimized CM NCs concentration is attributed to effective defect passivation, reduced VOC loss, and improved interfacial band alignment, which together facilitate hole extraction and suppress non-radiative recombination. However, excessive CM NCs incorporation (4 vol%) leads to increased interfacial resistance, partial hole blocking effects associated with the n-type nature of CeO2, and aggravated recombination, resulting in degraded device performance. These results demonstrate that precise control over CM NCs interlayer thickness and concentration is critical for maximizing device performance, providing a robust strategy for designing high-efficiency and stable NiOX-based PSCs and advancing nanocomposite-enabled interfacial engineering for photovoltaic applications.