| The perovskite solar cells have achieved significant progress as their appealing advantages of intense broad-band absorption,high charge carrier mobility and long charge diffusion length.As a result,the power conversion efficiencies（PCEs）have increased rapidly from 3.8% to over 21% within six years.With the speeding up to realize commercialization,the intrinsic toxicity and stability should be paid more attention besides the efficiency.Unfortunately,almost all of the high efficiency of perovskite solar cells were based on the traditional pure lead perovskite so far.As is known to all,the organic-inorganic hybrid metal halide perovskite matericals are easily soluble in water,which increases the risk of leakage even encapsulated.Thus,development of high effericiency lead-free and/or lead-less perovskite solar cells is imperative.Among numerous alternative elements of lead（such as: bismuth（Bi）,antimony（Sb）,cobalt（Co）,tin（Sn）,et al）,Sn was considered to be the most appropriate element as they all belong to the IVA group and have the similar ionic radii（Sn2+ 1.35 ? and Pb2+ 1.49 ?）,which may enable the substitution without significant lattice perturbation.Although the Sn element in perovskite materials is demonstrated to be not completely non-toxic,which is not due to the presence of heavy metal,but rather releasing of acidic HI that reduced PH value.This problem would be resolved by enhancing the stability of Sn-based perovskite solar cells.Besides,Sn is demostrated to be much easier cleared away from body in comparison to Pb,with the data that tin is less than 400 day whereas the lead is more than 20 years.So far,more and more researchers joined in the queue of lead-free and/or lead-less perovskite solar cells,and have gained lots of achievements,however,the PCEs are not are not competitive to the pure-lead perovskite solar cells due to the rapid crystallization.In this thesis,to decrease the rapid crystallization of Sn-based films,we have introduced a solvent engineering,which is by generating Pb I2/SnI2（DMSO）x complexes precursor,followed by molecular exchange to form high quality CH3NH3Pb1-xSnxI3(MAPb1-xSnxI3)perovskite thin-films.In the end,the MAPb0.75Sn0.25I3 perovskite solar cells with inverted structure were consequently realized with maximum power conversion efficiency（PCE）of 14.12 %.Further,we carefully investigated the detail carrier dynamics of both MAPbI3 and MAPb0.75Sn0.25I3,and analyzed the possible reason of hysteresis effect occurred even in the inverted structure.Finally,we introduced perovskite-C60 hybird to passivate the grain boundary and confront with oxygen and moisture in air,with the result of enhancing stability and reducing hysteresis of MAPb0.75Sn0.25I3 Perovskite Solar Cells. |
