Research On The Photoelectric Properties And Preparation Of The Perovskite Film Doped With Keggin Type Heteropolyacids

Although the research of the perovskite solar cell?PSCs?has made amazing progress in a short few years,the present power conversion efficiency?PCE?and rerproducibility of the PSCs cannot meet the needs of commercial application in future.Especially,the devices with large area still have relative low efficiency,which is still far less than the theoretical limitation.Based on the above-mentioned problems in the PSCs,this thesis mainly focus on the preparation and optimization of the films with HONH₃Cl addition,inverted thermal annealing?ITA?treatment and Keggin type heteropolyacids?HPA?doping for improving the photovoltaic properties in PSCs.Also,the relationship between the performance enhancement of the PSCs and dynamic behaviors of the photo-generated carriers were further systematically investigated.The perovskite film quality can be effectively improved by adding proper amount HONH₃Cl into perovskite precursor solution for one step spin-coating method.Compared with the pristine perovskite film,the prepared perovskite film exhibited a significant enhancement of the film quality with optimized surface morphology,reduced pinholes and improved crystallinity.In addition,the perovskite film optimized with HONH₃Cl addition showed improved optical properties and longer photoluminescence carriers lifetime based on the analysis of the UV-vis,photoluminescence spectrum measurements.Analyses of UV-vis spectra of the CH₃NH₃I solutions with different amounts of HONH₃Cl addition show that the HONH₃Cl addition can trigger a synergistic effect of various additives due the chemical reaction between HONH₃Cl and CH₃NH₃I or PbI₂.Finally,the corresponding PSCs obtained a largely enhanced photovoltaic performance with PCE improvement from7.8%to 11.1%,leading to a 42.0%PCE enhancement.As well,these devices simutaneously show good reproduciblity of the PCE results.The inverted thermal annealing method treatment can sufficiently utilize the residual solvents and reactant inside the film for ripening the the perovskite precursor film fabricated with two-step sequential spincoating method.Accordingly,the obtained perovskite film shows a reduction of surface roughness,particles boundaries and pinholes,increasing film coverage on the substrate and the improvement of the crystallinity of the perovskite crystalline.In addition,the convertion of the PbI₂ into perovskite can also be promoted.Based on the analysis of the UV-vis,photoluminescence spectrum measurements,the perovskite film treated with ITA method shows higher optical performance than that of the one treated with traditonal annealing?TA?method.The final PSCs constructed with ITA method obtain an enhanced photovoltaic performance with PCE increase from?11.4±1.1?%to?13.5±0.6?%with the highest PCE of 14.1%.In view of the intrinsic low charge mobility(10^-4cm·V^-1·s^-1)and electron extraction efficiency of TiO₂,the SiW₁₂-TiO₂ composites are constructed by adding heteropolyacid SiW₁₂2 into the TiO₂ paste?18-NRT?.Accordingly,the SiW₁₂-TiO₂ composites film shows slightly enhanced film quality,significant enhanced conductivity and electron extraction capacity.Consequently,the corresponding PSCs based on the SiW₁₂-TiO₂ composites mesoporous layer achieves a significant enhanced PCE from 12.0%to 14.7%.And the cell also shows a better stability in air.Likewise,by adding PW₁₂with higher conductivity than SiW₁₂into another TiO₂ paste?30-NRD?,the resulting PW₁₂/TiO₂ composites film shows improved film qulity,and the corresponding PSCs also presents boosted photovoltaic performance,with PCE enhancement from 14.0%to 16.1%in compasison with the pristine TiO₂.Electrochemistry impedance spectroscopy?EIS?and open circuit voltage decay measurements show that the charge transport properties in PSCs can be effectively improved,and the charge recombination is also inhibited.PSCs suffers from poor stability and reproducibility when place in dry air atmosphere for oxidizing the spiro-OMeTAD.Herein,Keggin-type heteropolyacid?HPA?-phosphovanadomolybdate(H₄PMo₁₁V·nH₂O,denoted as PMo₁₁V)is synthesized and for the first time employed as a p-type dopant for promoting the oxidation of spiro-OMeTAD.Thereby,without illumination and air,the conductivity and hole extraction efficiency of thePMo₁₁Vdopedspiro-OMeTADwithadditionoflithium bis?trifluoromethanesulfonyl?imide?Li-TFSI?and 4-tert-butylpyridine?TBP?can be dramatically enhanced.Based on this strategy,the corresponding PSCs exhibit substantially improved photovoltaic performance with good reproducibility.The best device yields a PCE of 14.1%.