Efficient and stable carbon-based perovskite solar cells enabled by the inorganic interface of CuSCN and carbon nanotubes

Hole transporting material (HTM) free carbon-based perovskite solar cells (C-PSCs) are one kind of promising candidates for new generation photovoltaic technology due to their superior long-term stability and low cost. However, the power conversion efficiency (PCE) of C-PSCs is significantly lower than that of HTM-based PSCs. This is mostly due to the unexpected electron recombination happening at the interface of perovskite/carbon. Moreover, the low conductivity of the carbon electrode slows down the charge collection process and results in a low fill factor and poor PCE. To address these concerns, we firstly inserted an inorganic CuSCN HTM between the perovskite and the carbon electrode to suppress the electron recombination process. Then we used a highly conductive carbon nanotube (CNT) network to form a robust interface of CuSCN/CNT and facilitate the hole collection process. As a result, the updated CuSCN and CNT incorporated C-PSCs exhibit a V_OC of 1.01 V and deliver a PCE up to 17.58% (measured in the backward scan) with pretty good reproducibility, which is the highest PCE in C-PSCs. What's more, the incorporation of CuSCN can also improve the stability of devices dramatically. The optimized device shows superior operational stability, retaining over 80% of its initial performance after 1000 h of continuous one sun illumination.