The Preparation And Study On The Absorption Layer Of Planar Heterojunction Perovskite Solar Cells

Solar energy is the most abundant energy that human can use. The process of development and utilization is healthier, safer and more environmentally friendly than other energy. Solar energy can be used to photoelectric conversion, solar-thermal conversion, photochemical transformation. Solar cells is the device that can be directly convert sunlight to power. Organic-inorganic halide perovskites solar cells have received considerable attention in recent years owing to their excellent optical and electronic properties including high absorption coefficient, low exciton binding energy, ambipolar charge transport, and long electron-hole diffusion length. At present there are still a lot of problems about perovskites solar cells because of its insufficient research. Therefore, it is important to reaearch the perovskites solar cells.Perovskite solar cells have many different structures and the preparation methods are also different. This article focuses on how to improve the uniformity, coverage, and roughness of the light absorption layer.(1) First, traditional one-step solution method was choosed to reaearch the perovskite layer. Due to the lack of suitable solvents that can dissolve both components, and the high reaction rate of the perovskite component, this process often lead to thin film with pinhole formation and incomplete surface coverage, which deteriorates the film quality and hampers the device performance. In order to make the precursor can quickly reach the supersaturated state, increase the density of nucleary and get the batter crystalline, the spin coating using the anti-solvent and hot air-assited spin coating method was choosed. Solvent annealing based on traditional one-step method was choosed to instead thermal annealing, because thermal annealing effectively increases the crystallinity and grain size of CH3NH3PbI3 film.(2)Secondly, using two-step method, including two-step solution method and vapor-assited solution process. Two-step solution method is spin CH3NH3 I solution on the PbI2 film, adjusting the concentration of a solution of CH3NH3 I as well as the spin time, to improve the quality of the film, the concentration of solution is 60 mM, and the adding time is 3s, the thin film is dense, but there are remaining PbI2 in thin film.The vapor-assited solution process can get compact and uniform films. The reaction mechanism which is make CH3NH3 I vapor reaction with PbI2 films was studied based on different reaction time in the 150 ℃.(3)The different lead sources were choosed to produce perovskite layer. PbCl2,Pb(CH3COO)2, PbNO3 was studied respectively. In the process of reaction, these three reaction with CH3NH3 I vapor can produces PbI2 mesophase. The complete reaction time was 60 min, 90 min and 120 min, respectively. Pb(CH3COO)2 and PbNO3 heated can easy formation of PbO, due to the stronger bonding strength of Pb-O than Pb-I,which lead to a longer time to complete reaction for CH3NH3PbI3.