The Preparation And Performance Of Absorbing Materials For Emerging Solar Cells

The great success of solar cells based on hybrid organic-inorganic lead halide perovskites has been achieved.However,the toxic issue of lead makes the solar cells hard to be further commercialized.Bismuth halide perovskites are considered to be a potential alternative to lead halide perovskites due to their similar crystal structures and the same electron configuration of Bi3+ as Pb2+.In recent years,bismuth based perovskite materials as new lead-free solar cell materials have attracted more and more attention of researchers.In this thesis,A3Bi2I9(A=Cs+,MA+)perovskite thin films were synthesized by spin-coating process.The crystalline phase,morphology,elemental composition and light absorption were analyzed by several methods such as XRD,SEM,EDS and UV-Vis.The results showed that A3Bi2I9(A=Cs+,MA+)perovskite films with good crystallinity can be obtained after annealing in air for 3h.The morphology of Cs3Bi2I9 was layered disc stacked by two-dimensional sheet with low surface coverage.UV-Vis tests showed that the absorption spectra of the A3Bi2I9(A=Cs+,MA+)annealed under vacuum conditions have a better absorption in 400-550nm than that annealed under ambient atmosphere.The morphology of Cs3Bi2I9 usually exhibits 2-dimensional(2D)layered flakes,which may be disadvantageous for using in solar cells.Herein,we show that thickness of the layered bismuth based perovskite crystals can be tuned by simply introducing thiourea as an additive into the precursor solutions.The morphologies of the perovskite crystals changed greatly with addition of thiourea,from the layered thin flakes to smooth thin disks,finally forming 3-dimensional(3D)large grains.In addition,the surface coverage of Bi-based perovskite films increased with the addition of thiourea,and UV-visible absorption spectrum was red-shifted.The short-circuit current density in a mesoporous architecture device increased from 0.81mA/cm2 to 2.19mA/cm2,and the photoelectric conversion efficiency was increased by 120%.As a light-absorbing layer material in solar cells,CuInS2 has attracted widespread attention because of its excellent performance.In this thesis,CuInS2 nanocrystals were prepared using solvothermal synthesis with indium chloride,cupric chloride and thiourea as raw materials and ethylene glycol or ethylene diamine as reaction solvents respectively.The effects of reaction time and reaction solvent on the phase,morphology and optical properties of CuInS2 were discussed.The results showed that Using ethylene glycol as solvent to react for 20 hours could obtain the chalcopyrite-structured CuInS2 nanocrystals.The morphology showed a flower-like microsphere formed by the agglomeration of thin nanosheets.The wurtzite-structured CuInS2 nanocrystals can be obtained using ethylenediamine as solvent,and the morphology showed uniform size nanoparticles.Both have good absorption in the visible light range.