Self-assembly monomolecular engineering towards efficient and stable inverted perovskite solar cells

Perovskite solar cells (PSCs) with monolayer-modified anodes are promising for high efficiency and stability devices with simplified configuration. Though preliminary studies on modified anodes by small organic molecules were reported, the goal-directed design and regulation of such compounds have been sparsely reported so far, thus limiting device performances. Herein, D-o-D type triphenylamine derivatives with non-conjugated linkage of sp³ oxygen are proposed to finely tune the energy level alignment and enhance the defect passivation at the ITO/perovskite interface, thus facilitating the efficient charge extraction at the anodes. The optimized molecules considerably ameliorate the photovoltaic performances of the corresponding inverted PSCs, engendering a preeminent power-conversion-efficiency (PCE) of 20.57% with negligible hysteresis. Remarkably, a good long-term stability is recorded for the unencapsulated device with over 94% of the initial PCE maintained after 180 days storage in N₂ condition. Those improved performances validate the feasibility of the D-o-D molecules for cost-effective PSCs with high-efficiency, and excellent long-term stability.