Research On Enhancement And Performance Of Charge Transport In Perovskite Solar Cells

Recently,the new generation solar cells based on CH₃NH₃Pb I₃ perovskite materials attract the extensive attention due to low cost and high absorption capacity.However,the power conversion efficiency（PCE）and ambient stability are the key factors remained to be solved.Hence,this thesis,focuses on investigating the optimal preparation method to improve hole transfer and collection as well as electronic transfer and collection,for the sake of improving the charge transport capacity of perovskite solar cells（PSCs）.In this thesis,we prepare PSCs by employing a composite hole transporting material（HTM）consisting of free standing Ni nanobelts.In order to prevent significant charge recombination induced by direct contact of the metal Ni with a perovskite absorber,a spiro-OMe TAD intermediate layer was spin-coated on the CH₃NH₃Pb I₃layer prior to the sequentially deposited layers of Ni nanobelts and spiro-OMe TAD.With this architecture,the optimized PSCs achieve a champion PCE of 16.18%with a short-circuit current density(J_SC)of 21.64 m A/cm²,an open-circuit voltage(V_OC)of1.02 V,and a fill factor（FF）of 73.3%under reverse scaning.On the one hand,it is resulted from electric conductivity of Ni,so that holes can be passed to the back electrode more efficiently.On the other hand,Strip avoids the mess of holes movement and shortening the distance.Additionally,the ambient stability of mesoscopic PSCs have been improved as well in the presence of highly hygroscopic lithium-bis（trifluoromethane）sulfonimide（Li-TFSI）,PSCs in conjunction with Ni nanobelts present an impressively favorable ambient stability with an observed PCE retention rate of over 85%after 4-week storage with exposure to ambient air without any encapsulation.The electronic transfer capacities of PSCs are enhanced by employing different weight ratios of co-axial nanofibers TiO₂/NSTO（0 wt%,2 wt%,7 wt%,15 wt%）.The results demonstrate that the optimal PCE of 16.19%is achieved by adding 7 wt%TiO₂/NSTO.The excellent PCE is owing to the higher electron mobility of NSTO,which accelerates transfer rates of the electrons from perovskite to the conductive substrate.In addition,the co-axial nanofibers TiO₂/NSTO can shorten the transporting distance among electrons,that the prepared PSCs perform excellent optical and electrical properties.