Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells

摘要

Solution-processed metal halide perovskite semiconductors, such as CH3NH3PbI3, haveudexhibited remarkable performance in solar cells, despite having non-negligible density ofuddefect states. A likely candidate is halide vacancies within the perovskite crystals, or theudpresence of metallic lead, both generated due to the imbalanced I/Pb stoichiometry whichudcould evolve during crystallization. Herein, we show that the addition of hypophosphorousudacid (HPA) in the precursor solution can significantly improve the film quality, bothudelectronically and topologically, and enhance the photoluminescence intensity, which leads toudmore efficient and reproducible photovoltaic devices. We demonstrate that the HPA canudreduce the oxidized I2 back into I�, and our results indicate that this facilitates an improvedudstoichiometry in the perovskite crystal and a reduced density of metallic lead.