A versatile energy-level-tunable hole-transport layer for multi-composition inverted perovskite solar cells†

Optimization of buried interfaces is crucial for achieving high efficiency in inverted perovskite solar cells (PSCs), owing to their role in facilitating hole transport and passivating the buried interface defects. While self-assembled monolayers (SAMs) are commonly employed for this purpose, the inherent limitations of single SAMs, such as fixed material structure and energy levels, hinder their adaptability and further efficiency enhancement across diverse compositions. In this study, we present an effective strategy of blending with SAMs with varying dipole moments to modulate the energy levels and hole transport properties, leading to enhanced charge transport characteristics and suppression of energy losses at buried interfaces. The intrinsic mechanisms of energy level modulation on the device performance are further investigated through theoretical simulations. Ultimately, small-area (0.0736 cm²) inverted PSCs with a 1.56 eV bandgap achieve a champion power conversion efficiency (PCE) of 26.28% (certified efficiency of 25.80%), while large-area devices (1.1 cm²) demonstrate an efficiency of 24.65%. Moreover, the energy-level-tunable SAM materials exhibit applicability across various PSCs with different preparation methods and bandgaps, achieving efficiencies of 24.44% for anti-solvent-free (1.56 eV) and 19.03% for wide-bandgap (1.85 eV) perovskite solar cells, respectively. Notably, devices employing these SAM materials demonstrate excellent photostability, maintaining over 95% of initial efficiency after 1000 hours of operation at the maximum power point (MPP).