2D/3D heterojunction engineering at the buried interface towards high-performance inverted methylammonium-free perovskite solar cells

The main bottlenecks limiting the photovoltaic performance and stability of inverted perovskite solar cells (PSCs) are trap-assisted non-radiative recombination losses and photochemical degradation at the interface between perovskite and charge-transport layers. We propose a strategy to manipulate the crystallization of methylammonium-free perovskite by incorporating a small amount of 2-aminoindan hydrochloride into the precursor inks. This additive also modulates carrier recombination and extraction dynamics at the buried interface via the formation of a bottom-up two-dimensional/three-dimensional heterojunction. The resultant inverted PSC achieves a power conversion efficiency of 25.12% (certified 24.6%) at laboratory scale (0.09 cm2) and 22.48% at a larger area (1 cm2) with negligible hysteresis. More importantly, the resulting unencapsulated devices show superior operational stability, maintaining >98% of their initial efficiency of >24% after 1,500 hours of continuous maximum power point tracking under simulated AM1.5 illumination. Meanwhile, the encapsulated devices retain >92% of initial performance for 1,200 hours under the damp-heat test (85 °C and 85% relative humidity).