Non-fullerene Ternary Organic Solar Cells Based On IDT Acceptors

Organic solar cells（OSCs）are one of the very potential and promising photovoltaic cell technologies,which are widely appreciated due to their light weight,easy fabrication,low cost,and the ability to be fabricated into thick films,flexible,and translucent devices.Ternary OSCs are fabricated into devices by selecting three organic semiconductors as acceptor materials,which not only retains the simple preparation process of binary OSCs,but also inherits the characteristics of the wide spectral absorption range of stacked OSCs.However,ternary OSCs still face the following problems:first,the device efficiency does not meet the international application standards;second,the interaction mechanism between materials is unclear;third,the device stability is not enough.This dissertation starts from high-efficiency binary OSCs,uses material selection and morphology optimization as research methods,and takes the collaborative optimization of photon capture,exciton dissociation,carrier transport and charge collection as the research direction to prepare high-efficiency ternary OSCs.As the ultimate goal,by preparing ternary OSCs of various systems,we explored the intrinsic reasons for the improved device performance of indahedodithiophene（IDT）non-fullerene acceptor materials as the third component.And,we revealed the intrinsic relationship between material properties,working mechanism and photovoltaic performance,which provided a good performance improvement strategy for the development of ternary OSCs in the future.The main research contents and innovations are as follows:（1）Using the highly crystalline IDT-like non-fullerene acceptor ITIC-Th as the third component,with the non-fullerene acceptor BTP-BO-4F,and the polymer donor PM6,a series of ternary OSCs were prepared.ITIC-Th acts as a morphology modifier to optimize the molecular alignment and phase separation of the device thin films.In addition,the introduction of a third component ITIC-Th with complementary spectral absorption broadens the spectral absorption range of the active layer.And ITIC-Th and BTP-BO-4F easily form an alloy state,which can inhibit the non-radiative recombination of the device.Finally,compared with BTP-BO-4F-based binary OSCs,the optimized ternary OSCs achieved a power conversion efficiency（PCE）improvement from 16.42%to 17.66%,mainly due to ITIC-Th as the third component,the photon trapping,exciton dissociation,carrier transport,and charge collection of the device are synergistically optimized,resulting in high-performance ternary OSCs.（2）Using the high LUMO IDT-like non-fullerene acceptor IT-M as the third component,together with the non-fullerene acceptor BTP-eC9 and the polymer donor PM6,a series of ternary OSCs were prepared.By adjusting the content of the non-fullerene acceptor IT-M in the active layer,the V_OC of ternary OSCs can be well enhanced and the charge transport of the device can be optimized to obtain high-performance ternary OSCs.Compared with the BTP-eC9-based binary OSCs with a PCE of 16.85%,a PCE of 18.73%was achieved in the optimized ternary OSCs with synergistic improvements in fill factor（FF）,short-circuit current density(J_SC).Finally,BTP-eC9-based binary OSCs adopted a ternary strategy to achieve a PCE improvement of more than 11%,which is mainly due to the complementary absorption spectra,good compatibility,and appropriate energy of three donor-acceptor materials in the device.