Fabrication Of Double-layer Perovskite Solar Cells And Their Photovoltaic Performances

Currently,environment pollution and energy crisis is becoming serious,and it is expected to relief the problems by the development of photovoltaic technology.Lead halide perovskite is an organic material with excellent properties,such as high light absorption and adjustable band gap,which has been widely studied recently for the use of photovoltaic devices.At present,there are some challenges,such as stability,repeatability,and the fabrication of high-quality large-area perovskite film.This thesis mainly focuses on the problems of repeatability and fabrication of high-quality large-area film.The specific research contents and results are as follows:(1)Single-layer and double-layer lead halide precursor films were deposited by evaporation-assistant method,and perovskite solar cells were fabricated by immerse method.The effect of rotation speed(first precursor layer),film composition and thickness(second precursor layer)on device performance were explored.It was found that the coverage of perovskite film was low after the reaction of single-layer lead halide film and the maximal power conversion efficiency(PCE)is only 10.2%,while the average open-circuit voltage(Voc)was only 0.9 V.When the double-layer lead halide precursor films were adopted,the coverage and compactness of perovskite films were greatly improved,and so does the Voc and PCE of cells.Meanwhile,we found that the surface morphologies have an important relationship with the composition of precursor films.When a Pbl2/PbBr2(spin-coating/evaporation,6000rpm/50nm)double-layer precursor film was applied,a continuous,dense and pinhole-free perovskite film was obtained.The corresponding device achieved a maximum efficiency of 15.4%and an average Voc of 1.02 V,and almost all devices had the Voc greater than 1.0 V.This work indicated that the evaporation-assistant method has high repeatability and reliability,which is potential to guide the fabrication of large-area high-performance perovskite solar cell.(2)The effects of DMF solvent annealing method,immerse method and vapor method on the quality,surface morphology and device performance of perovskite were investigated.It was found that the perovskite films will shrink and form linear structure after the treatment of DMF solvent annealing,resulting in low-coverage films and PCE decreaing from 10.2%to 0.4%of devices.Hence,the second lead halide layer was deposited to improve the coverage and it was converted to perovskite by immerse method and vapor method,respectively.The quality of materials fabricated by vapor method is bad due to the high temperature(160?),resulting in low performance of devices.In this work,devices fabricated by vapor method with 90 nm PbBr2 modification layer had a PCE of 6.7%.However,devices fabricated by immerse method with 100 nm PbBr2 modification layer had a PCE of 10.1%.This work showed that the second modification(evaporation-assistant method)can enhance the compactness of perovskite films and improve the device performance.