Improving The Efficiency And Stability Of Perovskite Solar Cells With Interface Engineering

Solution-processed thin-film solar cells based on organic-inorganic halide perovskite are emerging as a promising photovoltaic technology.During the past years,perovskite solar cells(PSCs)have attracted tremendous scientific and industrial interest,and the power conversion efficiencies(PCEs)have increased rapidly from?3.0%to 25%.Despite these advances and processing advantages,stability problems with PSCs are thought to be one of the most crucial issues before this technology can be commercialized.Interfaces have a critical influence on the properties and operational stability of metal halide perovskite optoelectronic devices.So this thesis pays attention to the interface engineering of metal halide perovskite solar cell.With the purpose on finding an efficient and universal protocol for fabricating perovskite solar cells with simultaneously enhanced efficiency and longevity.1.Through dissolving microscale functional conjugated polymer in antisolvent chlorobenzene to treat the spinning CH3NH3PbI3 perovskite film,the resultant device exhibits enhanced efficiency and longevity simultaneously.In-depth characterizations demonstrate that thin polymer layer is located on top surface of perovskite film,which plays an important role in surface passivation and modifying surface morphology.More importantly,an improved power conversion efficiency of 18.4%and 18.7%is achieved for p-type polymer PF-1 and n-type F-N2200,respectively,in comparison with 17.7%of device without any polymer.Relative to the efficiency improvement,the significantly enhancement of the device stability under either ambient environment or illumination is also achieved.2.By introducing a multi-functional dipole layer based on metallophthalocyanine derivatives copperphthalocyanine(CuPc)or highly fluorinated copper hexadecafluorophthalocyanine(Fi6CuPc).Both molecules were introduced through an"anti-solution" process to treat the surface of organic-inorganic CH3NH3PbI3 perovskite.The dipole layer can well align the interfacial energy levels,passivate the CH3NH3PbI3 surface and fill the grain boundaries,resulting in greatly suppressed charge recombination.As a result,our planar CH3NH3PbI3 perovskite devices exhibit a best PCE of 20.2%,with significantly enhanced open-circuit voltages(Voc)of 1.145 V(F16CuPc),which is a record high Voc value for CH3NH3PbI3 thin film solar cells.More importantly,the use of highly fluorinated F16CuPc dramatically improved long-term stability under ambient conditions.3.High quality CsPbI3 quantum dots are successfully synthesized and improved using in-situ Ytterbium doping strategy.Systematic investigations are carried out on the effect of Yb-doping engineering,the prelilinary experimental results indicates that Yb3+lanthanide cations can effectively reduce the defects and trap states caused by surface and lattice vacancies,leading to an improvement PCE and stability.The QD solar cells fabricated with 20%Yb-doped CsPbI3 QDs achieved the best PCE of 13.12%,meanwhile achieving a 60%initial PCE after 150 h storage in ambient conditions.4.We developed a high-efficiency lead halide perovskite QDs solar cells with a novel structure based on stacking CsPbI3 layer with FAPbI3 layer.We find that the FAPbI3 layer with narrow bandgap can expand the absorption range.While the CsPbI3 QDs layer can improve the PCE of the whole device.Interestingly,the layer-by-layer structure can build a graded interface to reducing the hysteresis of devices.Meanwhile,the stable FAPbI3 layer covering on the CsPbI3 layer can form a protective layer.Resultantly,a record PCE of 15.6%and significantly improved ambient stability of the binary perovskite QD solar cells were achieved.