Study On The Effect Of Graphite Carbon Nitride On The Photoelectric Properties Of Perovskite Solar Cells

At present,the photoelectric conversion efficiency of perovskite solar cells is developing rapidly.Due to its simple process,low cost and excellent photoelectric performance,it has attracted the attention of many researchers at home and abroad.The light absorption layer material of traditional perovskite solar cells is methyl lead ammonium iodide（CH₃NH₃Pb I₃）.Due to the intrinsic defects of the perovskite film,its photoelectric performance is reduced.Therefore,in order to improve the photoelectric performance of the perovskite film,passivation It is an effective solution to solve its defects.At present,adding passivation agents to perovskites is one of the effective methods,and the new semiconductor graphitic carbon nitride（g-C₃N₄）is an effective passivation agent.Here,a new idea is provided to study the improvement of the optoelectronic properties of perovskite thin films.The specific research contents and conclusions of this paper are as follows:（1）A two-dimensional semiconductor material,graphitic carbon nitride,was prepared by high-temperature calcination with urea as the precursor.Its forbidden band width is 2.7 e V,the band gap is adjustable,and it has excellent physical and chemical stability.Adding graphitic carbon nitride to the perovskite precursor solution at a certain concentration improves the crystalline quality of the perovskite film and reduces the intrinsic defect density of the perovskite film.In the experiment,the gradient doping concentration was set,and the optimal doping concentration of g-C₃N₄was found to be 0.5 wt%,and the photoelectric conversion efficiency of the perovskite solar cell increased from 10.75%to 11.61%.（2）Doping graphitic carbon nitride（g-C₃N₄）into the titanium dioxide（Ti O₂）electron transport layer can also improve the film formation quality of perovskite films.The g-C₃N₄/Ti O₂composite mesoporous layer was prepared by adding g-C₃N₄to the Ti O₂mesoporous solution at a concentration of 10 mg/m L and using glass-assisted annealing.Since the addition of g-C₃N₄reduces the band gap of the Ti O₂electron transport layer,the energy level matching between the electron transport layer and the perovskite layer is improved.At the same time,because the Ti O₂mesoporous layer is used as the substrate,the improvement of the substrate improves the quality of perovskite crystals and improves the optoelectronic properties of perovskite solar cells.The photoelectric conversion efficiency of the perovskite solar cell based on the g-C₃N₄/Ti O₂composite electron transport layer reaches11.40%,which is 27%higher than that of the cell based on the pure Ti O₂electron transport layer.（3）The g-C₃N₄was modified by element doping,using boron oxide as the boron source,and boron element was doped into g-C₃N₄without changing its two-dimensional structure.The obtained boron-doped graphitic carbon nitride has Excellent optoelectronic properties.Boron atoms were added to the molecular structure of g-C₃N₄by entering the structural gap and substituting C and N atoms at specific positions.Boron-doped graphitic carbon nitride（B-CN）was added to the perovskite precursor solution at the optimal doping concentration of 0.5 wt%,and the prepared perovskite layer had a smaller intrinsic defect density,and the calcium Compared with the doped original graphitic carbon nitride,the titanite film has a larger grain size and a smoother and denser surface.The photoelectric conversion efficiency of the perovskite solar cell based on boron-doped graphitic carbon nitride reaches 12.76%,which is 9.9%higher than that of the cell device doped with g-C₃N₄.