The synergistic strategy of hexaazatrinaphthylene-cyanoindone-based electron transporting material enabling efficient and stable inverted perovskite solar cells

The electron transporting material (ETM) plays a key role in the photovoltaic performance of inverted perovskite solar cells (PSCs), whose long-term stability, however, largely suffers from the diffusion of ions. We herein design and synthesize a non-fullerene ETM (2,2′,2′'-((2Z,2′Z,2′'Z)-((3,9,15-tris(hexylthio)diquinoxalino[2,3-a:2′,3′-c]phenazine-2,8,14-triyl)tris(methaneylylidene))tris(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))trimalononitrile, called HATIC) as both an additive of the perovskite layer and an electron transporting layer (ETL) for efficient and stable inverted PSCs. On the one hand, HATIC, as an additive, is able to effectively regulate the perovskite energy level alignment, decrease the trap density and reduce the diffusion of ions. On the other hand, HATIC, as an ETL, can efficiently extract and transport electrons due to its high electron mobility. Owing to this synergistic strategy, the target PSC based on HATIC as both an ETL and an additive obtains a power conversion efficiency of 23.07%, which is 10% enhancement relative to that for the control device based on 6,6-phenyl C61-butyric acid methyl ester (21.05%). Moreover, the target devices demonstrate much better long-term stability than the control devices due to the less diffusion of ions, lower trap density and slower charge recombination for the former. This work provides a new strategy for the development of efficient ETMs.