[22a-W531-1~11] 12.5 Organic solar cells

▲ [22a-W531-5] Rapid Perovskite Formation by CH₃NH₂ Gas-Induced Intercalation and Reaction of PbI₂

〇Yabing Qi¹, Sonia R. Raga¹, Luis K. Ono¹ (1.Okinawa Inst. of Sci. & Tech.)

Keywords:perovskite solar cells,chemical reaction mechanisms,CH3NH2 gas precursor

Solution processable perovskite solar cells traditionally use CH₃NH₃I solid powder as one of the two precursors that requires solvation into a solution and a spin-coating step; resulted films need post-annealing (~1h) for complete conversion to CH₃NH₃PbI₃. Here we describe a method to form perovskite in ambient air by exposing PbI₂ films to the simpler CH₃NH₂ gas precursor (as opposed to CH₃NH₃I solid powders) ¹. The reaction completes within a few seconds forming complete-coverage perovskite films with a roughness of 2 nm. The non-stoichiometric reaction produces Pb oxides as by-product, which are reconverted by further HI gas exposures. With combined measurements of thin film crystal structure, chemical state, and absorption properties, we elucidate the chemical reaction mechanisms underlying these gas-induced processes. Fabricated solar cell devices show efficiency of 15.3%, which stays almost the same after 133 days. Such a gas-induced reaction also enabled the successful preparation of high quality perovskite films with a size of 100 cm². We also demonstrate that this method is versatile and enables the formation of a wide range of perovskite materials, e.g. CH₃NH₃PbCl₃, CH₃NH₃PbBr₃, CH₃NH₃PbI₃, CH₃NH₃SnBr₃ CH₃NH₃PbBr_xI_3-x, CH₃NH₃PbBr_xCl_3-x.