The Preparation Of Key Materials And Device Integration Process In Low-cost And High-performance Perovskite Solar Cells

Perovskite solar cells(PSCs),one of the fastest growing photovoltaic technologies,have attracted great interest in the photovoltaic fields due to their high power conversion efficiency(PCE,25.2%).However,the problems of cost and stability hinder the commercial development of PSCs.Among many solutions,carbon-based perovskite solar cells(C-PSCs)have become the most promising methods due to their low cost and high stability.In this paper,we aim at solving a series of problems concerned with C-PSCs.We investigate and optimize electron transport layers(ETLs),perovskite layers,electrode layers and the integrated processes of the cell devices for fabricating the low-cost and high-performance PSCs.Details of research contents are as follows:(1)C60 is used to replace TiO2 ETL for forming the all-carbon based PSCs with the structure of FTO/C60/MAPbI3/carbon.C60 ETL could effectively improve electron extraction,suppress charge recombination,and reduce the sub-bandgap states at the interface with MAPbI3.Then,the all-carbon based PSCs achieve a PCE of 15.38%without hysteresis.Most importantly,the all-carbon based PSCs could maintain 95%of their initial PCE under 1 sun illumination for 180 h or in ambient condition for 20 days.Morever,we fabricate a more genuine all-carbon based PSC by using graphene transparent electrode,which also achieves a PCE of 12.67%.(2)We demonstrate a solution-processed ETL by doping C60 with hexamethonium bromide(HMB)to fabricate the C-PSCs with the structure of ITO/C60/CH3NH3PbI3/carbon.It is shown that doping of C60 with HMB carries several outstanding advantages,including faster charge transport,enhanced electron mobility,and the decreased electron trap density.The C-PSCs with HMB-doped C60 achieve a PCE of 16.03%,much higher than that of the PSCs with non-doped C60 ETL(12.22%).Moreover,the PSCs based on HMB-doped C60 could maintain 82%of their initial PCE in ambient condition over 60 days,and 90%of their initial performance under 1 sun illumination for 338 hours.(3)A short carbon-chain cation i.e.EA is introduced into 3D MAPbI3 to form a series of 2D-3D hybrid perovskites with general formulation(EA)2(MA)n-1PbnI3n+1.It is found that the fabricated(EA)2(MA)n-1PbnI3n+1 films(n=20,10,and 6)exhibit improved ambient and photo-stability in 60 day-ambient conditions.Further,the HTM-free C-PSCs with the structure of ITO/C60/(EA)2(MA)n-1PbnI3n+1/carbon achieve outstanding PCE over 11.88%.By tuning the stoichiometry of(EA)2(MA)n-1PbnI3n+1 to n=6,the resultant n6 C-PSC device retains the long-term stability of 93%under ambient conditions for 2160 hours,the thermal stability of 80%after continued 80? heating over 100 hours,and the photo-stability of 92%under continuous 1 sun illumination over 300 hours.(4)We introduce hydrophobic MWCNTs into the mixed FAxMA1-xPbIyBr3-y perovskite to achieve air preparation of a stable perovskite film,in which MWCNTs is added to the FAI:MABr precursor to mediate the crystallization of perovskite and facilitate formation of compact and large-size perovskite film.Interestingly,hydrophobic MWCNTs are found to be partly naked on the surface of perovskite films that can help perovskite films resist the erosion of moisture.Such stable air-processed mixed perovskite films then are implemented into HTM-free C-PSCs in ambient environment,achieving all-air processed photovoltaic devices with the remarkable PCEs of 16.25%(0.08 cm2)and 12.34%(1.00 cm2).Morever,the fabricated mixed cation C-PSCs maintains the long-term stability of 93%during 22 weeks.(5)We fabricate a 1D-2D hybrid AgNWs-G transparent electrode instead of common ITO electrode by simple sequential spin-coating process.Graphene film was spin-coated onto glass/AgNWs substrates,which can contribute to polishing the surface of AgNWs film and preserving AgNWs from degradation.By optimization,the compact and smooth AgNWs-G-2 film achieves a lower Rs of 11.0 ? sq-1 than that of ITO(13.5 ? sq-1),and a relatively high transmittance of 86%.Compared with pristine AgNWs film,AgNWs-G-2 film exhibits fantastic stability of Rs within the entire duration of air exposure,even though at high temperature and continuous illumination.The low-cost AgNWs-G-2 electrode film is implemented into HTM-free C-PSCs with the structure of AgNWs-G/SnO2/perovskite/carbon,achieving an outstanding PCE of 15.31%and a long-term stability of 88%for 60 days in air conditions.