Origanic-Inorganic Hybrid Perovskite Solar Cells Based On Improved Perovskite Films

Among emerging solar cells,the power conversion efficiency(PCE)of perovskite solar cells(PSCs)has rapidly increased in just a few years due to the excellent optoelectronic properties of perovskite materials.The PCE has been vastly jumped from 3.8%to 25.2%in 10 years.The perovskites exhibit great photoelectric characteristics,such as the adjustable band gap,outstanding optical absorption factor,long carrier diffusion length,low temperature preparation and so on.The performance of organic-inorganic halide perovskite solar cells is significantly influenced by the crystallization and morphology of perovskite films.In this master's thesis,a N-I-P type structure perovskite solar cell is used.A novel method of CsPbBr3 quantum dots(QDs)assisted nucleation is applied to prepare high quality solution-processed methylammonium lead iodide(MAPbI3)films by employing CsPbBr3 QDs as an additive into diethyl ether anti-solvent.The appropriate amount of CsPbBr3 QDs can act as effective heterogeneous nucleation centers,leading to the formation of smooth and pinhole-free perovskite films with increased grain size.The heat treatment process of perovskite films was studied by using different atmospheres,which effectively solved the problem of poor film coating caused by excessive humidity and improved the repeatability of preparing high quality perovskite films.Finally,the use of mannitol dissolved in the perovskite precursor as a water absorbing agent improves the stability of perovskite films.The main contents are as follows(1)Based on the N-I-P type configuration of ITO/SnO2/MAPbI3/spiro-OMeTAD/Au,CsPbBr3 quantum dots with high quantum dot yield,high color purity and better stability are used as heterogeneous nucleation centers of MAPbI3 films.The purpose of optimizing the nucleation process of perovskite film by adding CsPbBr3 quantum dots to the diethyl ether anti-solvent.Compared to pure DE anti-solvent,the introduction of CsPbBr3 QDs provides a certain number of heterogeneous centers,and the nucleation of perovskites becomes thus easier in the periphery of CsPbBr3 QDs,which plays a vital role in preparing of pinhole-free and smooth MAPbI3 films with increased grain size and preferred(110)orientation.The champion PSC with a maximum PCE up to 20.17%with the addition of CsPbBr3 QDs,which increases by nearly 10%compared with the referenced device,and exhibits good stability.(2)Based on the structure of ITO/PCBM/MAPbI3/spiro-OMeTAD/Au,the effects of different atmospheres on the heat treatment process of perovskite films were investigated.The quality of the finally obtained perovskite film was analyzed by introducing different atmospheres(Air,O2,CO2 and N2)immediately after spin-coating the perovskite and simultaneously performing heat treatment at 100?Tests have shown that both air and O2 accelerate the decomposition of the perovskite film.However,N2 and CO2 can provide protection and the grain quality is higher,and in high humidity environments,the use of N2 and CO2 can make the preparation of perovskite films more reproducible.(3)The mannitol was used as an additive into MAPbI3 perovskite precursor solution to improve the humidity stability of perovskite films.Mannitol and water were extracted using ethyl acetate as an anti-solvent.Reduce the risk of film decomposition by moisture.The final assembled device structure was ITO/SnO2/MAPbI3/spiro-OMeTAD/Au.After adding mannitol,the encapsulated device shows good stability under continuous illumination.