Inkjet Printing Of Perovskite Solar Cells And Study Of Quinoidal Thiophene Dyes For Small-molecule Organic Photovoltaics

Due to high cost of conventional silicon-based photovoltaic technology,solution-coating technologies have been explored for the development of large-area and low-cost solar cells.Organic photovoltaics(OPV),dye-sensitized solar cells(DSSC)and recently developed perovskite solar cells(PSC)are extensively studied.Among them,high photovoltaic conversion efficiencies of more than 10% have been achived for DSSC and OPV,and efficiencies of up to 20% were reported for PSC.Based on the background,two aspects of research work in this thesis were studied as follows:(1)Inkjet printing is a material-conserving deposition technique used for control deposition,enabling easy and fast deposition of functional materials on various substrates with large area.Here,perovskite(CH3NH3PbI3)active layer was inkjet printed on nanoporous TiO2 films: firstly,PbI2,CH3NH3 I and CH3NH3 Cl were dissolved in ?-butyrolactone with a molar ratio of 1:(1-x):x(0≤x<1(8).The precursor solution was deposited on TiO2 film by inkjet printing.The effects of in situ heating temperature and the additive(CH3NH3Cl)were studied on the structure and morphology of the perovskite films.The results showed that the optimized temperature is around 50 ℃,and the desirable x is 0.6 for the deposition of high quality perovskite films.Under the optimized conditions,the perovskite solar cells exhibited a best PCE of 12.3% under AM 1.5G conditions,with high reproducibility(averaged PCE,11.2%).The current work demonstrated that the inkjet printing is an environmentally sound technique for the fabrication of efficient low-cost and large-scale perovskite solar cells.(2)Two small molecular quinoidal thiophene dyes,QT-4(Mw=354)and QT-5(Mw=478),featuring quinoidal thiophene as a spacer,(N,N-diethylamino)benzene or [N,N-bis(p-methylphenyl)amino]benzene as an electron donor moiety,and ethyl cyanoacetate as an electron acceptor moiety,have been synthesized as donor materials for organic photovoltaics.Both the dyes feature: 1)simple chemical structures,low molecular weights,and easy syntheses.Compared with conventional polymeric or small molecular donor materials,the dyes can be easily prepared with low cost.2)The dyes have broard absorption spectra,enabling efficient harvesting of photons with different energy in solar radiation spectra,and potentially increasing solar to electrical conversion efficiency.3)They have high solubility in polar or non-polar solvents,enabling solution deposition of the solar cells.Solar cells with configuration of ITO/PEDOT:PSS/QT-4 or QT-5:PC71BM/Ca/Al were prepared.By optimization of solvents,annealing technology,ratios of donor and acceptor,and the solution concentrations,the solar cells exhibited a preliminary PCE of 2.53% under AM 1.5G conditions.