Interface Engineering And Lead-Free Investigation Of All-Inorganic Perovskite Solar Cells

Organic-inorganic hybrid perovskite(ABX3)materials have attracted great attention in recent ten years due to its excellent photoelectric properties,such as high light absorption coefficient,high carrier mobility,long carrier diffusion length and adjustable band gap.The power conversion efficiency(PCE)of perovskite solar cells(PSCs)has increased from 3.8%in 2009 to certified 25.2%in 2019.Currently,the research on PSCs focuses on efficiency,stability,large-area fabrication and lead-free.Perovskite solar cell devices have a "sandwich" structure consisting of an electrode/charge(electron or hole)transport layer/perovskite photoactive layer/charge(hole or electron)transport layer/electrode.It is found that interface engineering is one of the effective strategies to improve device efficiency.In addition,the toxicity of lead has always been a key concern for the commercialization of PSCs,and the development of new lead-free perovskite solar cells is also the focus of current research.In this dissertation,we carried out works focusing on organic-inorganic hybrid,all-inorganic and new lead-free PSCs from the aspects of interface engineering,material preparation.The main research contents and results are as follows:1.Fabricating n-i-p inorganic(CsPbI2.25Br0.75)PSCs using 3,3-diphenylpropylamine(DPPA)-modified ZnO as electron transport layer(ETL).After DPPA modification,the conduction band(CB)of ZnO increases,matching well with the CB of perovskite,which is benefit for reducing energy loss.Meanwhile,the formation of Zn-N bonds can reduce the defects on ZnO surface,resulting in suppressed interfacial charge recombination.CsPbI2.25Br0.75 film on modified ZnO exhibits improved crystallinity,larger grain size and reduced trap density.CsPbI2.25Br0.75 solar cells with modified ZnO ETL delivered a high PCE of 15.98%.Besides,using DPPA-modified ZnO as ETL,CsPbI2Br solar cells gave a PCE of 14.86%with an impressive Voc of 1.27 V.2.Fabricating inorganic PSCs with a structure of ITO/SnO2/ZnO/CsPbI2.25Br0.75/HTL/MoO3/Ag.PTAA doped with polymer donor PBD2T(D-PTAA)was used as hole transport layer(HTL).The deeper highest occupied molecular orbital(HOMO)level of PBD2T provides a better energy level matching with CsPb12.25Br0.75,thus reducing the energy loss.In addition,sulfur(S)atoms in PBD2T could passivate the trap states on perovskite surface effectively via Cs-S and Pb-S bonds,thus reducing the interfacial charge recombination.CsPbI2.25Br0.75 solar cells with D-PTAA HTL delivered a high PCE of 17.37%with a fill factor of 80.14%.3.A new photovoltaic material CsAg2Sb2I9 was developed.And the influence of CsI content in the precursor solution on the film morphology and device performance was investigated.Films with different molar ratios of CsI:AgI:SbI3 were fabricated(0.4:2:2,0.8:2:2,1:2:2,1.2:2:2,1.6:2:2,2:2:2,4:2:2).The optimal molar ratio is 1:2:2,which possesses the best coverage and the lowest roughness.The best CsAg2Sb2I9 solar cell gave a PCE of 0.99%.4.Non-fullerene-receptor materials(COi8DFIC,ITIC,IT-4F)were used to replace PC61BM as the ETLs for Cs3Sb2I9 solar cells.Due to the wide bandgap of Cs3Sb2I9,the photoresponse of Cs3Sb2I9 solar cells is narrow.Non-fullerene receptor material has good light absorption in the near infrared,which can broaden the photoresponse and improve the short-circuit current.The performance of Cs3Sb2I9 solar cells based on non-fullerene receptors were better than that of PC61BM(1.38%).Thanks to its high light absorption coefficient and electron mobility,solar cells based on IT-4F delivered a best PCE of 2.15%,whose short-circuit current was increased from 4.57 mA/cm2 to 7.11 mA/cm2.