High Photovoltage of 1 V on a Steady-State Certified Hole Transport Layer-Free Perovskite Solar Cell by a Molten-Salt Approach

The determination of certified efficiency values for perovskite solar cells from current–voltage sweeps is under growing discussion. Here, we report for the first time a certified steady-state solar efficiency for a hole transport layer (HTL)-free perovskite cell of 12.6% measured continuously at maximum power point in an accredited laboratory. By applying a molten-salt-based MAPbI3 precursor solution, dense filling and improved perovskite crystallization inside the nanoporous graphite-based monolithic contact scaffold of the cell are achieved. A stabilized photovoltage as high as 1 V is achieved, representing the highest VOC reported for HTL-free MAPbI3-based devices. Charge transport properties are determined by switching from open- to short-circuit conditions. Strong and stable quenching of the photoluminescence indicates effective transportation and extraction of the photoexcited primary charge carriers. The existence of an efficient HTL-free device suggests that these cells are more of an n-p junction type than of n-i-p junction nature.