Impact of self-assembled monolayer structural design on perovskite phase regulation, hole-selective contact, and energy loss in inverted perovskite solar cells

Recent studies have shown that self-assembled molecule (SAM)-based hole-selective contacts (HSCs) offer a promising solution to the challenges faced by perovskite solar cells (PVSCs), including minimal material consumption, scalable production, high interface stability, and the use of environmentally friendly solvents. In this study, the efficacy of two designs of SAMs (Cz and PA) as HSCs in inverted PVSCs was investigated by comparing them with the conventional MeO-2PACz (MeO) SAM. Surface analyses showed that the surface of PA is smoother than that of Cz, which helps to reduce interfacial defects. Subsequent perovskite deposition exhibited a reduced formation of the PbI₂ phase, incidiating that its phase modulation ability is superior to that of MeO. Further analyses demonstrate the superior charge extraction ability of PA as a result of reduced interfacial defects and non-radiative recombination at the HSC/perovskite interface. By further coupling with phenethylammonium iodide (PEAI) surface passivation, both interfaces of the perovskite film were optimized and the inverted ((FAPbI₃)_0.85(MAPbBr₃)_0.15)_0.95(CsPbI₃)_0.05 (bandgap = 1.62 eV) PVSC achieves a high power conversion efficiency (PCE) of 23.3 % and a very high open-circuit voltage of 1.227 V due to the largely reduced energy loss. In addition, the PA PVSC exhibits enhanced long-term thermal stability at 85°C in a nitrogen atmosphere.