Tuning The Morphology Of Active Layer Regulated By Intermolecular Interactions And The Effect On The Photoelectric Performance Of Solar Cells

As a kind of green renewable energy,organic solar cells have become a research hotspot in the field of renewable energy because of their advantages such as easy processing,flexible devices and rich material selection.How to improve the photoelectric conversion efficiency of solar cells and maintain high stability is the main research direction.In this paper,the main starting point is to regulate the morphology of the active layer,take the Flory Huggins interaction parameters as the reference basis to characterize the internal structure of the active layer,and regulate the degree of phase separation and the continuity of the internal interpenetrating network of the active layer film by adjusting the solubility parameters of the donor or receptor.In this paper,discoid liquid crystal molecules with D-A structure and assembly characteristics are used as the third component to construct ternary organic polymer photovoltaic devices to explore their mechanism of action on devices containing fullerene receptor systems and non-fullerene receptor systems.Inspired by this,we further studied the effects of different types of solvent additives on non-fullerene receptor system devices with the help of interaction parameters,and further selected non fullerene receptors as the third component to study the effects on photovoltaic devices.The main research contents of this paper are as follows:（1）Firstly,the discoid liquid crystal material（TP-2-PIE）with self-assembly ability and receptor（D-A）structural unit was carefully selected as the third component to be added to the active layer based on fullerene receptor heterojunction(PTB7-Th:PC₇₁BM)to construct ternary solar cells.It is found that liquid crystalline TP-2-PIE has multiple functions,which can significantly improve the performance of bulk heterojunction organic polymer solar cells based on fullerene receptors.The absorption complementarity of TP-2-PIE and the energy transfer between TP-2-PIE and PTB7-Th improve the photon capture ability and the JSC of the device;The addition of TP-2-PIE component changes the interaction parameters between donor and acceptor molecules in the active layer,which can regulate the morphology of the active layer,obtain appropriate phase separation and improve phase purity,help to balance carrier transport and reduce the density of trapped states.When the content of TP-2-PIE is 10 wt.%of the donor,the performance of the device is optimal,and its photoelectric conversion efficiency is 12.6%higher than that of the binary(PTB7-Th:PC₇₁BM)basic device.（2）The discoid liquid crystal material（TP-1-PIE）with self-assembly ability and D-A structural unit was carefully selected as the third component to be added to the active layer based on non-fullerene acceptor heterojunction（PM6:Y6）to construct ternary solar cells.It is found that TP-1-PIE molecule has similar multiple functions,which can significantly improve the performance of bulk heterojunction organic polymer solar cells based on non-fullerene receptors.The absorption of TP-1-PIE and PM6:Y6 is complementary,which improves the photon capture ability of the active layer,especially the photoinduced charge transfer process between TP-1-PIE and PM6,which helps to increase exciton dissociation,which is conducive to the improvement of J_SC.TP-1-PIE can form an alloy structure with active layer materials to realize the regulation of V_OC of devices.According to the changes of solubility parameters and V_OC,TP-1-PIE formed an alloy with Y6,and its receptor structural group on the molecule participated in the regulation of V_OC.In addition,the addition of TP-1-PIE component changes the interaction parameters,improves the flatness of the active layer and the continuity of the interpenetrating network,reduces the density of trap states,effectively reduces the recombination in carrier transmission,and improves the carrier mobility.When the TP-1-PIE content is 20%,the photovoltaic response of the device reaches the optimum,and the photoelectric conversion efficiency is 16.68%,which is 15%higher than that of binary（PM6:Y6）basic devices.（3）With the help of Flory Huggins interaction parameters,the effects of different solvent additives on the performance of solar cells based on non-fullerene acceptor heterojunction（PM6:Y6）were studied.In this study,chloronaphthalene（CN）containing benzene ring and 1,4-butanediethiol（BDT）,1,8-diiodooctane（DIO）,1,8-dibromooctane（DBr O）and1,8-dichlorooctane（DCl O）containing alkyl chain were selected as solvent additives to study the effects on device performance.The results show that CN containing benzene ring mainly acts on the donor PM6.With the increase of CN content,the solubility parameter of pm6 decreases,making the interaction parameter between PM6 and Y6 increase,which is conducive to the phase separation of the active layer and obtaining a wider range of crystal domains.The four additives containing alkyl chain have a great influence on the receptor Y6.The solubility parameter of Y6 increases with the increase of the proportion of additives,and the effect of DBr O additive is the best.Adding 0.5 vol%DBr O can increase the filling factor of the device to 77.13%,and the photoelectric conversion efficiency to 15.42%,which is 16.3%higher than the basic device without solvent additives.（4）By analyzing a series of solubility parameters of donor receptors,and based on this,non-fullerene receptors were selected as the third component and added to PM7:Y7 bulk heterojunction to construct ternary organic polymer solar cells.It is found that IT-4F,which has good compatibility with the receptor,can improve the performance of the device as the third component,while BTP-e C9,which has poor compatibility with the acceptor,cannot improve the performance of the device as the third component.In addition,the absorption spectrum of IT-4F is complementary to PM7:Y7,which improves the photon capture efficiency.The addition of IT-4F reduced the interaction parameters between donor and acceptor,smoothed the film morphology,and improved the exciton dissociation efficiency.When PM7:Y7:IT-4F=1:0.8:0.4,the performance of the device is optimal,and the photoelectric conversion efficiency is16.92%,which is 16.8%higher than that of the binary basic device.There are 58 figures,38 tables and 169 references in this work.