Defects And Interfacial Regulation Of High Efficiency And Stable Perovskite Solar Cells

Organic-inorganic metal halide perovskite semiconductor materials with low defect density,high extinction coefficient,small exciton binding energy,low cost,solution processing and excellent photoelectric conversion efficiency attach great importance of many scientific researchers,and quickly become one of the most promising candidates in the third generation photovoltaic technology industry.In the last decade,the power conversion efficiency（PCE）of photovoltaic devices based on perovskite materials has increased from 3.8%to 25.7%,manifesting its great potential for practical application.However,the poor repeatability and long-term stability of high efficiency devices of perovskite solar cells（PSCs）seriously restrict their further development and applications in various photoelectric devices.Therefore,in addition to ensuring high-efficiency device performance,solving the long-term stability of PSCs in the air is a key issue that many researchers are focusing on at present.The current research results show that the defects of perovskite film due to more grain boundaries and degradation of organic transport layer materials are the main reasons affecting the photovoltaic performance and stability of perovskite solar cells.The additive engineering,interface engineering and inorganic and stable carrier transport layer constructing are considered as effective means to solve the above problems.Herein,in this dissertation,the modification of all-inorganic carrier transport layer in perovskite solar cells and the defect passivation in the perovskite film are mainly employed to improve the power conversion efficiency and long-term air stability,and the following research results are obtained:1.The perovskite film with larger grain size,lower defect density and excellent water resistance was effectively constructed by adding polyphenylene derivatives to the perovskite active layer.It was found that the decrease in the density of defect states in these perovskite films is likely due to the efficient coordination between the carboxylic groups in the polymer and the uncoordinated Pb²⁺cations in the perovskite.The power conversion efficiency of the obtained inverted planar heterojunction PSCs with all inorganic charge extraction layer could be increased to 20.41%.Most importantly,the optimized device retains 90%of its initial PCE value after aging in air for 60 days,which attributes to its dual moisture resistance mechanism.This work lays the foundation for the development of high-performance PSCs with higher stability in the air and paves the way for their potential commercialization.2.The inverted planar PSCs of Cu doped nickel oxide（Cu:Ni O）and W doped niobium oxide（W:Nb₂O₅）inorganic carrier transport layer（CSLs）as holes and electron transport layer were prepared by a double-source electron beam co-evaporation method.The optimized CSLs are highly conductive low defect,and compatible with the perovskite active layer,which can effectively realize the transportation and collection of photogenerated carriers.In addition,the perovskite active layer matches the Fermi level of CSLs,which leads to a significant improvement(e.g.V_oc,FF,and PCE)of photovoltaic device performance.Meanwhile,the introduction of an ultra-thin titanium（Ti）buffer layer in the electron transport layer（ETL）and the electrode further improved the efficiency and stability of the perovskite solar cell,increasing to 21.32%of device performance,and the hysteresis is suppressed.Moreover,the PCE of the doped CSLs based device could reach up to 19.01%at an effective area of 1?cm~2.Most importantly,the encapsulated and unencapsulated devices retained 98%and 89%of the initial PCE after being exposed in humid（50%±10%）air for 1200 h,demonstrating their excellent long-term stability.3.The perovskite film with decreased defect density was effectively constructed by introducing 1-butyl-3-methyl imidazolium tetrafluoroborate（BMIMBF₄）ionic liquid into the perovskite precursor solution,improving the carrier life and chemical stability of the perovskite film.Meanwhile,an ultrathin layer of cesium-lead mixed halide（Cs Pb Br₃）quantum dot ink was inserted between ETL and perovskite film,further promoting the PCE and moisture stability of PSCs.As a result,the PCE of an inverted-planar heterojunction all-inorganic perovskite solar cell with the BMIMBF₄-doped perovskite as active layer and Cs Pb Br₃ as the interlayer,could reach to 15.37%,accompanied by the reduced the hysteresis.In addition,due to the enhanced moisture resistance,the optimized perovskite film retains 80%of the initial PCE after aging in air for 60 hours.In conclusion,this work achieves the improvement of device moisture resistance and the reduction of trap state density through a collaborative approach,developing high-performance inorganic PSCs,which can provide ideas for the research of various kinds high-efficiency photoelectric materials.