Non-fullerene Organic Solar Cells Based On New Small Molecule Acceptor INTIC And INTzIC

Organic photovoltaic devices have received more and more attention because of their advantages of light weight,low cost,simple process,easy preparation of flexible devices and easy mass production.In the early stage of the research,fullerene materials have been widely used as acceptors in the field of organic photovoltaic research due to their superior electron transport capability.However,the limitations of fullerene acceptors such as low light absorption,not easily adjustable molecular energy levels and high synthesis cost have limited their development.To further improve the performance of organic photovoltaic devices,researchers are concentrating to develop new non-fullerene acceptors which should maintain the advantages of fullerene's efficient charge transfer ability and good blending morphology with the donor material.In addition,it would have the advantages of easy synthesis,higher optical absorption and easy regulation of molecular energy level.However,many high-performance small-molecule materials require complex processing in their center D unit,so it is still a challenge to develop a non-fullerenes material that is easy to synthesize.Indeno[1,2-b]indole(IN)has been proved to be a readily available structural unit in the preparation of non-fullerenes.Our collaborators found that A-?-D-?-A compounds with IN-centered electron-rich aromatic nuclei(i.e.,INTIC and INTz IC)exhibited strong and wide near-infrared absorption.When PTB7-Th was used as the donor,the average power conversion efficiency of the organic solar cells using INTIC and INTz IC as the acceptor materials was 6.87%and 6.60%respectively.The maximum efficiency of PTB7-Th:INTIC based organic photovoltaic devices is 7.27%.In order to further optimize the small molecule INTIC system,we have selected three other polymers PTB7,PBDB-T and PBDB-T-2F as donor materials with INTIC as the acceptor to prepare organic solar cells with the same structure to optimize their photovoltaic performance.The experimental results show that the best photoelectric conversion efficiency of organic solar cells based on PBDB-T:INTIC is 11.08%.According to the experimental results,compared with the devices with PTB7-Th:INTIC as the active layer,the open circuit voltage of PBDB-T:INTIC based cells increases from 0.80V to 0.84V,the short-circuit current increases from 15.32 m A/cm~2 to19.42 m A/cm~2,the filling factor increases from 60.08%to 67.89%,and then the efficiency increases by 52.4%.It is because that the PBDB-T:INTIC system has a better carrier dissociation,transportation and extraction.By comparing the photovoltaic devices prepared by the four donor systems,we found that the appropriate donor is very important for the preparation of cells with high photovoltaic performance by the acceptor INTIC(low cost,strong infrared absorption capacity of the receptor).