Design And Optimization Of Hole Transport Layer For High-performance P-i-n Perovskite Solar Cells

Perovskite materials have been used as the light absorbing layer of solar cells due to their excellent photoelectric properties.The current maximum power conversion efficiency（PCE）of perovskite solar cells（PSCs）has reached up to 25.2%recently,which reveals their great potential in the future energy field.In order to promote holes extraction and transportation and suppress-the moisture and oxygen penetration,it is crucial to seek suitable materials for the fabrication of hole transport layer（HTL）and modify their interface for the improved efficiency and stability of PSCs.Therefore,this thesis includes the following three aspects:（1）The HTL with gradient energy structure was fabricated in situ by low temperature annealing,which effectively promotes exciton separation and improves the hole extraction efficiency.The open circuit voltage(V_oc)andc（PCE）of the devices reached up to 1.02 V and 18.0%,respectively.In addition,due to better hydrophobicity and lower acidity of VO_x,PSCs based on gradient energy level structure exhibit good long-term stability.The devices remain 80%and 70%of the initial PCE in N₂ for 750 h and in air for 175 h,respectively.（2）Since poly[bis（4-phenyl）（2,4,6-trimethylphenyl）amine]（PTAA）is a relatively hydrophobic polymer,the perovskite film based on PTAA exhibits poor morphology and low surface coverage,resulting in low device performance and reproducibility.In this part,the VO_xprepared from organic vanadium salt is used to modify the PTAA to form composite HTL,which effectively improves the wettability of the surface of HTL.The optimized devices show increased V_oc to 1.12 V and PCE up to 18.9%.Meanwhile,VO_x layer also significantly improves the device reproducibility.（3）In order to improve the crystal quality of perovskite,for the reduced the energy loss and non-radiative recombination,the newly developed organic small molecule（（9H-carbazol-9-yl）diphenylphosphine oxide）was chosen used as the hole-transport material.By systematically adjusting the energy level of the composite with PTAA to form a suitable hole transport layer,the maximum PCE of the optimized device is as high as 21.7%.Furthermore,the device has very good stability,which maintains 85%of the initial PCE after storring in the ambient condition（40%humidity at room temperature）for 750 h.