Study On The Fabrication Technologies Of CH₃NH₃PbI_3-XCl_X Perovskite Solar Cells

At present, the development of human beings is faced with the dual problems of the increasing shortage of fossil and the increasingly serious environmental pollution, so it is imperative to develop renewable energies. In a variety of new energy technologies, photovoltaic power generation is undoubtedly one of the most promising directions. Among a large number of solar cells, the perovskite solar cell is developing at the fastest pace. Its power conversion efficiency enhanced from 3.8% to 21% in just 6 years, since first reported in 2009, which makes this new type of solar cells become the new star in photovoltaic field.In this paper, we choose the type of CH3NH3PbI3-xClx perovskite solar cell as the research object. The preparation technologies of perovskite solar cells with different structures including normal structure and inverted structure were studied, respectively. And on the basis of the optimized preparation technology of the inverted perovskite solar cells, we combined the two methods of thermal annealing and solvent annealing which promote the crystallization of perovskite thin films, putting forward a new method named solvent-assisted thermal annealing. We used this method in preparing CH3NH3PbI3-xClx perovskite solar cell, and achieved remarkable results.To optimize the fabrication technologies of the normal structure of planar heterojunction perovskite solar cells, Titanium isopropoxide and TiCl4 were used as the sources of TiO2 block layer, respectively. Under the optimal conditions, the conversion efficiency of perovskite solar cells which used the TiCl4 as the titanium sources reached 7.55%. The conversion efficiency of perovskite solar cells reached 7.81% when Titanium isopropoxide served as the source of titanium. Through the further optimization processes of the light absorption layer of perovskite and a hole transport layer, we finally prepared CH3NH3PbI3-xCIx perovskite solar cell with normal structure whose conversion efficiency reached 9.02%.Through a series of the optimizations for fabrication process, the conversion efficiency of inverted perovskite solar cells with a structure of FTO/PEDOT:PSS/ CH3NH3PbI3-xClx/PCBM/Al reached 11.84%, which laid the foundation for the subsequent research of STA method.Under the optimal preparation conditions of inverted perovskite solar cells, we introduced the STA method to treat the perovskite thin films, which effectively improved the performance of inverted perovskite solar cells. The best conversion efficiency reached 13.45% which was 14% higher than that of optimal cell just with thermal annealing.Through a series of characterization technologies such as XRD, SEM, UV-vis, PL and so on, we discovered that the STA method can effectively promote the crystallization of perovskite. It made the perovskite grains thick and dense, which suppressed the generation of defects and reduced the probability of carrier recombination, enhanced the photocurrent.