The Fabrication And Study Of High Performance Perovskite Solar Cells:Morphology Control And Interface Engineering

Organic-inorganic hybrid perovskite had been developed rapidly these 10 years,and the efficiency has been exceeded 24%recently,which is comparable to the polysilicon solar cells.The nonradiative charge recombination,which is mainly caused by the trap-state and insufficient charge extraction,is the main reason for the energy loss for perovskite solar cell(PVSCs).In this manuscript,we aim to improve the efficiency by morphology control and interfacial engineering.In the case of perovskite morphology control,we firstly simplified the anti-solvent process by replacing the antisolvent(chlorobenzene)to PCBM/chlorobenzene.As a result,the PCBM layer would retard the evaporation of the DMSO and keep the film in"wet state" for longer time,which would promote the merge of the small crystals,and leading to the high quality perovskite grain and the boost of the efficiency from 9.49%to 12.68%.This work simplified the fabrication process.In addition,we also improve the host cast method,and successfully achieved a high efficiency of 19.56%with an 850 nm thick perovskite layer.We found that the hot cast method would result in the monolithic perovskite films with single crystal cross profile which would significantly reduce the charge recombination and energy loss.As a result,the PVSCs made by hot cast method exhibit thickness insensitive property,the efficiency could keep at the high level of 19%when its thickness varying from 700 nm to 1150 nm.The excellent thickness insensitive property would also overcome the disadvantage of thickness varying problem in large scale manufactory technology.As for the interfacial engineering,we spin coated a very thin layer of polymer(PTAA,PMMA,PS)on the rough NiOx layer.The polymer would fill the gaps and holes between the NiOx grain,which is the main resource for the trap state.As a result,the efficiency had been improved from 19.23%(NiOx)to 21.56%,21.21%and 20.84%for NiOx/PTAA,NiOx/PMMA and NiOx/PS,respectively.Besides the gap fill advantage,PTAA could also lower the HOMO level of the NiOx layer to better match with the perovskite.As a result,the energy loss would be reduced and a high Voc of 1.19V could be obtained.While for PMMA,the ester group in the side chain could make a coordination with Pb2+ and passivate the defect in perovskite layer.Therefore,the Voc of NiOx/PMMA devices could also reach to 1.19 V.This work provide a simple and efficient method to improve the property of the NiOx layer and is helpful for the reduction of the energy loss.We also studied the effect of substrates on the property of the 2D perovskite layer(BA2MA2Pb3I10).We found that the substrate would not influent the crystalline and orientation of the 2D perovskite,but it would influent the phase distribution and surface property,such as energy levels and surface morphology.For the perovskite growth on NiOx,it has a more dense surface without pinhole,which means less trap state.And the perovskite on NiOx had a better energy level alignment with the hole transport layer and electron transport layer,which eventually improve the efficiency of 8.99%(PEDOT:PSS)to 11.01%.In addition,we take advantage of PCBM’s high mobility and ICBA’s high hole block ability by mixing them.We used this mixed electron transport layer to further reduce the interfacial recombination and boost the efficiency to 12.07%with a device structure of ITO/NiOx/BA2MA2Pb3I10/PCBM:ICBA/BCP/Ag.The efficiency of 12.07%is the high value for the BA2MA2Pb3I10 based perovskite,and the Voc is 1.23 V,which is the highest value for the 2D PVSCs so far.This work implies the importance and great potential for the interfacial engineering for 2D PVSCs.