Preparation And Photoelectric Properties Of CH₃NH₃PbI₃ Perovskite Materials

Organic-inorganic hybrid perovskite materials,as direct band gap semiconductors,have high optical absorption coefficient,long charge-diffusion distance,and high carrier mobility.The bandgap of CH₃NH₃PbI₃ perovskite material is about 1.5 eV,and it can absorb the sunlight from the near infrared to the ultraviolet range.Using the CH₃NH₃PbI₃ perovskite material as the light absorption layer can obtain good photoelectric devices.We have prepared solar cells based on the CH₃NH₃PbI₃ perovskite material and optimized their preparation process.Perovskite solar cells containing the mesoporous PCBM scaffold were prepared by co-annealing the PCBM and CH₃NH₃PbI₃ perovskite material,and the CH₃NH₃PbI₃ perovskite single crystals were prepared by heating the saturated precursor solution and their properties were characterized.The main content focuses on the following aspects:（1）The PEDOT:PSS or PTAA used as the hole transport layer and CH₃NH₃I solutions with different concentrations,thermal annealing and solvent annealing methods were used to prepare the CH₃NH₃PbI₃ perovskite films and solar cells.It was found that using the CH₃NH₃I solution with suitable concentration and solvent annealing can obtain larger perovskite grains and increase the current density of solar cells,and using PTAA as the hole-transport layer can obtain larger open circuit voltage and higher solar cell efficiency.Solvent of different volume was dropped during the solvent annealing,the PCBM or polystyrene solution was spin-coated on the perovskite films,and SiO₂ with different thickness was vapor-deposited on the perovskite films to optimize the solar cells process.（2）The CH₃NH₃PbI₃ perovskite films containing the mesoporous PCBM scaffold were prepared by the PCBM co-annealing method,and the corresponding solar cells were prepared.The perovskite films formed by PCBM co-annealing were divided into upper and lower layers,the upper layer was perovskite grown in the mesoporous PCBM scaffold,and the lower layer was a relatively dense perovskite layer.Since the films were uneven,there was a large hysteresis in the solar cell prepared by PCBM co-annealing.After spin-coating PCBM on the co-annealing films,the film undulations were reduced and the mesoporous PCBM scaffold still existed.The hysteresis of the solar cell prepared by the aforementioned method was small,and the photoelectric conversion efficiency reached 16.1%.（3）CH₃NH₃PbI₃ perovskite single crystals were prepared by antisolvent vapor-assisted crystallization and heating saturated solution.Perovskite single crystals larger than 5 mm were obtained by heating saturated solution method and seed crystal growth.The optical absorption edge of the single crystal perovskite was 818 nm,while the optical absorption edge of the film perovskite was about 775 nm,and the single crystal perovskite can absorb the incident light in a larger wavelength range.