Preparation And Performance Research Of Organic Solar Cells Based On Non-Fullerene Acceptor Materials

Among many new energy technologies,organic solar cells(OSCs)have attracted considerable attention of researchers due to their unparalleled advantages of semitransparent,light weight,low cost,and potential for making large-area flexible devices.Recently,power conversion efficiency(PCE)of the OSCs has been rapidly improved owing to the design and development of non-fullerene acceptors(NFAs),but its efficiency is still lower than that of inorganic silicon solar cells.The active layer materials of OSCs are the most important part of photoelectric conversion.Therefore,the research and development of narrow-bandgap non-fullerene acceptors and wide-bandgap polymer donors with complementary absorption and matched energy levels is an effective way to improve device efficiency.In this thesis,we carried out research work from donor and acceptor of the active layer,and systematically explored the influence of the morphology of the active layer on the photovoltaic performance of the device.The main results are as follows:(1)A new acceptor-donor-acceptor(A-D-A)structured NFA,named BTC-2F,was designed and synthesized by introducing chlorine atoms into the thiophene conjugated side chains of its central donor unit.The effect of chlorine substitutions on acceptor properties was studied.Relative to non-chlorine acceptor BTH-2F,BTC-2F exhibited slightly blue-shifted absorption spectra,enhanced extinction coefficient,deeper highest occupied molecular orbital(HOMO)energy level,and higher electron mobility.A wide-bandgap polymer PM6,was selected as the donor material to construct bulk heterojunction OSCs processed with non-halogenated solvent toluene.The optimized OSC based on PM6:BTC-2F showed a higher PCE of 12.9%with an open-circuit voltage(VOC)of 0.92 V,short-circuit current(JSC)of 20.3 mA cm-2 and fill factor(FF)of 69.3%,while the PCE of the PM6:BTH-2F-based device was only 11.3%after additives and thermal annealing treatments.And the device efficiency based on PM6:BTC-2F remained 11.0%when the thickness of the active layer increases from 80nm to 200nm.At the same time,OSCs based on two aeceptors exhibited good storage stability.(2)The bithiazole(BTz)as acceptor unit was incorporated into the D-A copolymer PM6 backbone to synthesize the D-A1-D-A2 terpolymers PT1(20%BTz)and PT2(40%BTz).The influence of BTz content on polymer properties was studied.With increasing of BTz content,the absorption of the polymer showed gradually blue-shift,the molecular energy level slightly shifted upward.And PT1 had smaller molecular stacking distance and enhanced hole mobility than that of PM6.The optimized OSC based on PT1:Y6 showed a higher PCE of 17.10%with a JSC of up to 26.26 mA cm-2,an FF of up to 76.6%than that of OSC based on PM6:Y6(PCE=15.73%)with JSC of 25.60 mA cm-2 and FF of 72.4%.The optimized OSC based on PT2:Y6 only obtained a much lower PCE of 15.50%(VOC=0.85 V,JSC=25.32 mA cm-2,FF=72.0%).