Photovoltaic performance of lead-iodide perovskite solar cells fabricated under ambient air conditions with HTM solution excluding LiTFSI

Organic-inorganic lead halide perovskite solar cells (PSCs) have attracted a great deal of interest because of their potential low cost and high efficiency. However, in most publications, solar cells were fabricated in a highly controlled environment (glove boxes). To reduce the production cost, it is suggested to fabricate PSCs under ambient air conditions; however, some of the materials are highly sensitive to the humidity of ambient air conditions. Lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) is one of these materials that usually is used as a dopant in hole-conductor solutions. In this paper, we have studied the performance of PSCs fabricated under ambient air conditions without using LiTFSI in hole transport material (HTM) solutions. This means we have stored the materials, prepared the solutions, and fabricated the devices all under ambient air conditions. In this work, spin-coating speed for deposition of the HTM layer, HTM solution preparation, the effect of HTM exposure to air and light, and the repetitive measurement of cells are investigated. We found that exposure of samples to air and light is both crucial for fabrication of solar cells with larger current density and better fill factor. These results are important toward fabrication of low-cost high-efficiency PSCs under ambient air conditions.