The Research Of IDT-based Intermediate Band Gap Acceptor Materials And Photovoltaic Performance Of Ternary Organic Solar Cells

Organic solar cells（OSCs）,as a new energy technology,are currently a hot research topic in the energy field.Their advantages mainly include wider material sources,lighter weight,simple device processes,flexible and translucent preparation,etc.Thanks to the continuous development of non-fullerene receptor materials and new device processes,the power conversion efficiency（PCE）of OSCs has been increasing,However,compared with other photovoltaic devices,OSCs have some problems such as poor photon utilization and large voltage losses,leading to poor device PCE.The research shows that the ternary strategy can make up for the shortcomings in binary and tandem devices,and it’s a simple and effective way to enhance the photovoltaic performance.In this paper,according to the basic design principles of ternary devices,a medium-bandgap non-fullerene acceptor with complementary absorption,matching energy levels and suitable crystallinity is selected as the third component to obtain high-efficiency ternary organic photovoltaic devices.The paper describes the effects of the third component material selection and device optimization on the photovoltaic performance of ternary devices,and explains the influence of carrier dynamics processes,energy loss,and active layer morphology on device performance.Details of the study and results are as follows.（1）IDIC-C4Ph,a small molecule of bandgap non-fullerene receptor in the IDT class,was selected as the third component and added to the PM6:Y6 binary device to construct a ternary device,and it was found that IDIC-C4Ph could compensate for the deficiencies of photon utilization in PM6:Y6 binary device at the mid-wavelength position,thus it can improv the short-circuit current(J_SC)of the device,Meanwhile,IDIC-C4Ph has higher lowest unoccupied molecular orbital（LUMO）compared to Y6,which is beneficial to increase the device open circuit voltage(V_OC);notably,the PM6:Y6:IDIC-C4Ph ternary device have excellent active layer morphology,which is beneficial to improve the exciton dissociation efficiency and enhance the charge transport capability.In particular,the higher and balanced carrier mobility can suppress charge recombination,which facilitates the device to obtain higher fill factor（FF）.When the ratio D:A₁:A₂=1:1.2:0.15,all three photovoltaic parameters of the ternary device are fully enhanced compared to the binary device,with the best PCE of 18.10%,J_SC of 26.65 m A cm^-2,V_OC of 0.872 V,and FF of 77.85%for the triplet device.Importantly,the ternary device maintains more than 90%of the initial PCE after 45 days of storage in nitrogen environment.The work in this section shows that IDIC-C4Ph as the third component is an effective strategy to enhance the photovoltaic efficiency and device stability.（2）The bandgap non-fullerene small molecule receptors PZ-d IDTC6-4F and PZ-d IDTC6-4Cl in the IDT class were used to act as the third component and added to the PM6:Y6 binary system to construct ternary device.It was found that the two molecules were compatible with the energy levels of PM6 and Y6,and their absorption spectra were complementary.when D:A₁:A₂=1:1.2:0.2,the results showed that the PCE of the two types of ternary device based on PM6:Y6:PZ-d IDTC6-4F/PM6:Y6:PZ-d IDTC6-4Cl reached17.65%and 17.51%,respectively.Compared to PCE of binary device,The main reasons for the PCE improvement of ternary device are that it compensates for the insufficient absorption of medium wavelength sunlight,the stepwise arrangement of energy levels to increase the charge transfer paths while improving the V_OC,the smaller roughness of the surface,the suitable phase separation size and a good interpenetrating network structure.The work reveals the feasibility of a class of mid-bandgap non-fullerene acceptors as a third component to construct high-performance ternary device.