Role of surface recombination in perovskite solar cells at the interface of HTL/CH3NH3PbI3

In order to achieve the highest performance of organometal trihalide perovskite solar cells, it is required to recognize the dominant mechanisms which play a key role in a perovskite material. In the following studies, we have focused on the interfacial recombination between the hole transporting layer (HTL) and the perovskite CH3NH3PbI3 in solar cell devices with p-i-n architecture. It has been shown that Cu:NiOx used as HTL drastically decreases a short-circuit photocurrent (J(sc)) and an open-circuit voltage (V-oc). However, we have found that an addition of PTAA thin layer improves cells quality and, as a consequence, the efficiency of such solar cells increases by 2%. Here, we explain both J(sc) and V-oc losses with a theory of the "dead layer" of perovskite material where a very high surface recombination occurs. We demonstrate the numerical and experimental studies by the means of series detailed analyses to get in-depth understanding of the physical processes behind it. Using a drift-diffusion model, it is shown that the presence of a parasitic recombination layer influences mostly the current distribution in the simulated samples explaining J(sc) and V-oc losses. The following results could be useful for improving the quality of perovskite solar cells.