Morphology Optimizaiton Of The Active Layer In Organic Solar Cells By The Dual Effect Of Solid And Solvent Addiitives

As a renewable energy technology,Organic Solar Cells(OSCs)have attracted enormous attention due to its advantages of light-weight,low cost and solution processing.In recent years,the design and synthesis of photovoltaic materials,especially the development of novel non-fullerene acceptors,have made the energy conversion efficiency(PCE)of single junction OSCs exceed 19%.As an important part of OSCs,photoactive layer plays a vital role in the photovoltaic conversion process.The morphology of the blend film with appropriate phase separation and phase region size can significantly improve the charge transfer characteristics and reduce the charge recombination to obtain high efficiency organic photovoltaic devices.Therefore,fine-tuning the morphology is critical for the improvement of PCE of organic solar cells.In order to prepare high-efficiency OSCs,it is necessary to optimize the morphology of the active layer according to the characteristics of donor and acceptor materials.In this thesis,we took the high-performance non-fullerene system as the research object,studied the morphology regulation of the active layer,compared the effects of different optimization methods on the morphology of the active layer,and provided some references for optimizing the morphology of the active layer of the non-fullerene system.The main research results are described in the following:(1)According to the similar anisotropic conjugated structures and small solubility differences between non-fullerene acceptors and p-type organic semiconductor donors,we developed a new morphology regulation method.The high crystallinity dithieno[3,2-b:2’,3’-d]thiophene(DTT)was exploited as a solid additive in coordination with 1-chloronalin(CN)solvent additive to optimize the morphology of the active layer of the non-fullerene system.The volatile solid additive DTT can limit the excessive self-assembling of non-fullerene acceptors during the film casting process of the active layer,and the DTT volatilizes after thermal annealing,so as to optimize the phase separation and molecular accumulation of the blend film,improve the carrier mobility and the hole and electron mobilities tend to be more balanced.Therefore,the PCE and filling factor(FF)of the device are significantly improved.Among them,the ternary OSCs based on PTQ10:m-BTP-Ph C6:PC71BM treated with CN and DTT dual additives obtained 18.89% high PCE and 80.5% high FF.(2)Three solid additives with similar structure were selected:thieno[3,2-b]thiophene(TT),benzo[1,2-b:3,4-b:5,6-b]trithiophene(BTT)and DTT,which were used as dual additives with CN solvent additives to regulate the morphology of high-efficiency non-fullerene active layer.The effects of three solid additives on the molecular stacking,active layer morphology and photovoltaic properties of the device were explored from the perspective of intermolecular interaction.Theoretical calculation and test results show that there are intermolecular interactions between the three solid additives and the non-fullerene acceptors,and the interaction forces increase in turn.The synergistic effect of the three solid additives and CN solvent additive can improve the morphology of the active layer,make the molecular stacking more orderly,and the carrier mobility is higher and more balanced.Therefore,the FF and PCE of the device are increased.Among them,the intermolecular interaction force between DTT and non-fullerene acceptors is greater,so the photovoltaic performance of the OSCs treated with CN and DTT dual additives is the highest.The OSCs based on PTQ10:Y6(o-xylene)obtained 79.2% high FF and16.82% PCE with the treatment of CN and DTT.