Constructing m-TiO2/a-WOx hybrid electron transport layer to boost interfacial charge transfer for efficient perovskite solar cells

Recently, the rapid improvement in power conversion efficiency (PCE) of perovskite solar cells (PSCs) with surprising and efficient PSCs is considered to be the most promising alternative to the next generation photovoltaic. In PSCs, the interfacial charge transfers between perovskite and electron transporting layers (ETLs) play an important role in enhancing the PCE, hysteresis, and stability. Here, an amorphous WOx (a-WOx) interlayer is interposed between the perovskite layer and mesoporous TiO2 (m-TiO2) layer to boost the hetero-interface charge transport. The room-temperature processed a-WOx has a wide bandgap and high electron mobility, which is capable of efficiently transporting photo-generated electrons, thereby reducing interfacial charge accumulation in the PSCs. Besides, we first found that the m-TiO2/a-WOx hybrid ETLs have better non-wettability, which subsequently improves the crystallization of the perovskite films by promoting the grain boundary mobility. Consequently, under optimized MAPbI3 solar cells having m-TiO2/a-WOx hybrid ETLs exhibits the highest Voc of 1.16 V and the PCE of 20.98%. Stability tests indicate that the PCE value based on the m-TiO2/a-WOx device remains more than 91% after exposure to 45% humidity for 30 days in the dark at room temperature, much higher than the m-TiO2 based cell, which retains about 70% of the initial PCE value.