Boosting efficiency of p-i-n perovskite solar cells via enhanced interfacial dipole strength using Al2O3 nanoparticles

Interfacial engineering plays a crucial role in enhancing the performance of perovskite solar cells (PSCs) by optimizing energy alignment and charge transport at the interfaces. While self-assembled monolayers (SAMs) have emerged as effective hole transport layers (HTLs) due to their interfacial dipole effect, the impact of dipole strength optimization on device efficiency remains insufficiently explored. In this study, we present a simple yet effective strategy to enhance interfacial dipole strength in p-i-n PSCs by incorporating aluminum oxide nanoparticles (Al2O3 NPs) as spacers within the Me-4PACz interfacial layer. This approach leads to the formation of a thickened dipole layer, significantly improving energy level alignment and charge extraction. As a result, the power conversion efficiency (PCE) of the PSCs increased from 22.61 % in control devices to 25.59 % in optimized devices. Furthermore, we demonstrate the universality of this strategy by applying it to 2PACz and MeO-2PACz based PSCs, achieving efficiency improvements of 7.2 % and 5.8 %, respectively. This work provides new insights into interfacial dipole engineering, offering a scalable and efficient approach to advancing high-performance PSCs.