Regulation Phase Separation Structure Of Active Layer Of Organic Semiconductor Photovoltaic Device

The nanostructure of the active layer of an organic semiconductor photovoltaic device has an important influence on its energy conversion efficiency.In the all-polymer blend system,the molecular crystallization behavior can induce the occurrence of large-scale phase separation,which is not conducive to exciton diffusion? Since an organic semiconductor photovoltaic device is usually prepared by solution processing to prepare an active layer,the solution state and film forming kinetics have a decisive influence on the phase separation structure of the active layer.The main research content is as follows:1.We used solution temperature control and thermal annealing to achieve the small interphase size and highly crystalline interpenetrating network structure of the PBDB-T/P(NDI2OD-T2)blend system through solid-liquid phase separation type control and limited crystallization principles.Studies have shown that when the solution temperature is between 80 °C and 120 °C,PBDB-T does not undergo solid-liquid phase separation,while P(NDI2ODT2)undergoes solid-liquid phase separation;Spin coating at this time due to the presence of P(NDI2OD-T2)crystal nuclei in the solution can induce further crystallization,so P(NDI2ODT2)to form a crystalline network structure and PBDB-T filled in between the small size of the network structure.On this basis,the film was thermally annealed,which promoted the limited crystallization of PBDB-T inside the P(NDI2OD-T2)crystal network,thereby forming a small-size,high-crystalline,interpenetrating network structure.By controlling the state of the solution solution and using limited crystallization,a small-size,high-crystallinity interpenetrating network structure can be obtained,and the device performance is also improved from 5.33% to 7.12%.2.The molecular orientation of the PBDB-T/P(NDI2OD-T2)blend system was optimized by synergistically adjusting the state of the solution and the film formation kinetics,and the relationship between the relative molecular orientation of the acceptor and the device performance was established.When we add the small molecule additive diphenyl ether(DPE)to the donor/acceptor blend solution,the degree of aggregation of the P(NDI2OD-T2)molecule gradually decreases,and the resulting film molecular orientation changes from faceon to edge-on.For PBDB-T films,their molecular orientation is edge-on and does not change with additive content.The solvent vapor treatment further improved the crystallinity of the blended film,and the device performance was further improved to 7.46%.