Ideality Factor Mapping of Back-Contact Perovskite Solar Cells

摘要

The efficiency of back-contact perovskite solar cells has steadily increasedover the past few years and now exceeds 11, with interest in these devicesshifting from proof-of-concept to viable technology. In order to make furtherimprovements in the efficiency of these devices it is necessary to understandthe cause of the low fill factor, low open-circuit voltage (V_(OC)), and severe hysteresis.Here a time-dependent Suns-Voc and Suns-photoluminescence (PL)analysis are performed to monitor the transient ideality factor spatially. Twosets of quasi-interdigitated back-contact perovskite solar cells are studied;cells with and without a mesoporous TiO_2 layer. Maps of the PL intensity andideality factor resemble the periodic structure of the back-contact electrodesand the transient behavior exhibit distinct features such as a temporary variationin the periodicity of the modulation, spatial phase shifting, and phaseoffsets. It is shown that the presence of the mesoporous layer greatly reducesrecombination, increasing the V_(OC) by 0.12 V. Coupled 2D time-dependentdrift-diffusion simulations allow the experimental results to be modeled, andreplicate the key features observed experimentally. They reveal that non-uniformion distribution along the transport layer interfaces can drastically alter thePL intensity and ideality factor throughout the device.