The relatively lower crystallinity and random orientation of quantum well structures hinder carrier transport and limit the performance of formamidinium (FA) based low‐n 2D perovskite devices. In this work, the crystallization and quantum well orientation are fine tuned to achieve efficient low‐n FA based Ruddlesden–Popper perovskite solar cells. The effects of different ionic additives on the crystallization, orientation, and photovoltaic performance of FA based low‐n 2D perovskites are comparatively investigated. It is found that NH4+ and SCN− can significantly retard the heterogeneous crystallization of low‐n phases in the intermediate state, and drive the templated growth of quantum well structure with vertical orientation. The optimized photovoltaic device based on (BA)2(FA)3Pb4I13 achieved a power conversion efficiency (PCE) of 18.14%, setting the highest record for FA‐based low‐n 2D perovskite solar cells as far as it is known (average n = 4). The unencapsulated device exhibited excellent stability and maintained 93.3% of its original PCE at 85 °C, and 86.3% at 1 Sun illumination after 720 h in humid ambient condition.
High quality buried interface is crucial for highly efficient, stable, and scalable perovskite solar cells, especially for p-i-n structure devices. Here, we report a buried interface engineering by doping tetrachloroaluminate...
Nonradiative recombination losses at defects in metal halide perovskite films are responsible for hindering the improvement of the photovoltaic performance and stability of perovskite solar cells (PSCs). Here, we report a feasible multifunctional additive strategy that uses cesium stearate to passivate defects in perovskite films and simultaneously enhances the tolerance to light and moisture stress. Nonradiative recombination losses are effectively suppressed in target films that exhibit improved crystallinity, low trap-state density, and enhanced carrier separation and transportation. The present strategy hence boosts the power conversion efficiency of the pi-n structured PSC to 23.41%. Our device also shows good stability in ambient air without encapsulation, maintaining 91.6% of the initial efficiency after 720 h.
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