Preparation And Properties Of Doped Ytterbium Hydroxide As The Hole Transport Layers Of Perovskite Solar Cells

The consumption of non-renewable energy sources and environmental problems have become urgent in recent years as the use of fossil fuels has increased rapidly.As an inexhaustible source of clean energy,solar energy has received much attention from researchers.Perovskite solar cells have been considered as a solution to this problem due to their low costs,simplicity of preparation and high solar energy conversion.In perovskite solar cells,the hole transporting layer plays an essential role in transporting holes and inhibiting interfacial junction formation,which directly affects device performance.Organic hole transport material has been widely used but is not suitable for commercial applications owing to its complicated preparation process,poor stability and high cost.This makes research into inorganic hole transport materials with low cost,simplicity and stability extremely important.In this thesis,an easy to prepare,durable and low-cost inorganic Yb（OH）₃ material is used as a hole transport layer and the effect of doping on improving the material performance and inverted device efficiency is studied.The main research work carried out in this thesis is as follows.:（1）Yb（OH）₃ and copper-doped Yb（OH）₃（Yb（OH）₃:Cu）nanoparticles were synthesized by a hydrothermal method,and uniform and dense hole transport layers were prepared by spin-coating the dispersions,which were applied to inverted perovskite solar cells for the first time as hole transport material with the device structure of FTO/HTL/PVK/PEAI/PCBM/BCP/Ag.Yb（OH）₃ is found to have low electrical conductivity and poor hole transport capacity,and Cu²⁺ion doping can significantly improve the hole transport capacity of Yb（OH）₃.Meanwhile,Cu doping can modulate the energy level position of Yb（OH）₃,optimise the energy level matching between Yb（OH）₃ and perovskite interface and improve the interfacial hole extraction process.In addition,the deposition of perovskite films on the surface of the Yb（OH）₃ hole transport layer is also influenced by the substrate composition,and copper ion doping can promote grain growth and crystallinity improvement of the perovskite films.The copper doping improves the device interface hole extraction process and suppresses the intra-device compounding process,which increases the efficiency of the corresponding perovskite solar cell from 8.71%to 17.09%.（2）Based on the previous work,Yb（OH）₃:Cu/In nanoparticles were prepared by hydrothermal method to further investigate the effect of In3+ions on the performance of Yb（OH）₃:Cu hole transport layer.The valence band position of Yb（OH）₃:Cu was further decreased after introducing In³⁺ions,which better matched the valence band energy level of perovskite,avoiding energy loss and promoting hole collection interface.Simultaneously,the conductivity of the hole transport layer is further increased and its hole transport capability further improved.Morphological and physical analyses of the perovskite films show that In³⁺ions promote perovskite film growth and crystallisation.By assembling inverted structured perovskite solar cells,it was found that the carrier complexation process and the interfacial charge extraction process could be further improved after doping with In³⁺ions.The device efficiency was increased from 17.09%to 18.54%under optimum conditions.This work opens up more possibilities for the selection of hole transport materials,as there are few reports on the use of hydroxides as hole transport materials in perovskite solar cells.