Design And Synthesis Of Non-fullerene Acceptor Materials Based On Benzothiophene Small Molecules And Applications In Organic Solar Cells

High performance non-fullerene acceptors?NFAs?have acheived particular attention and interest in the field of organic photovoltaics?OPV?during the last years.Numerous advantages over the most common fullerene acceptor derivatives,including tunable frontier orbital energy levels,intense absorption,smaller voltage losses,and even better thermal and photophysical stability,have been demonstrated.Benefitting from the great progress in material development,high power conversion efficiencies?PCEs?exceeding 16%have been reported recently,indicating the potential to push the efficiency to the stage of commercial application by exploring novel NFAs.Small molecule non-fullerene electron acceptor materials with different band-gaps and energy levels were designed and synthesized.The details are as follows:?1?We designed and synthesized a series of narrow-bandgap small molecule acceptors?IDT-C8,IDT-DTM,IDDT-DTM?.PCEs of 3.13%,3.06%,and 4.14%,respectively,were achieved with using PBDB-T as the donor polymers.The contact angle have tested and shown that the material is less well-sticked,which is the reason why the device current and fill factor are poor.Although there is an efficiency-gap between high-efficiency non-fullerene polymer solar cells in papers and this work,it is also a critical step to exploring the high-efficiency OPV devices.?2?Here,we present the design and synthesis of two analogous wide-bandgap SMAs,IDT-TBA?1.91 eV?and IDTT-TBA?1.78 eV?.PCE values of 6.7%and 7.5%were achieved when PBDB-T was used as the electron donor polymer.^[54]The results are quite prominent for wide-bandgap SMA-based cells.Further photophysical experiments demonstrated high external charge generation efficiency?EGE?values exceeding 90%for both acceptors,indicating reduced geminate recombination.It is noted that although there is still an efficiency gap to the most efficient fullerene-free polymer solar cells,this study demonstrates attractive potentials and significance of wide-bandgap SMAs and opens up a promising avenue to explore wide-bandgap NFAs for efficient OPV devices.?3?In this section we designed and synthesized two wide-band gap non-fullerene small molecule acceptors?IDDT-T-TBA?1.78 eV?and IDDT-TC6-TBA?1.74 eV??.We used a mode of single-donor with PBDB-T and double acceptors with ITIC and target compound to exploring the potential of this materials in ternary devices.Because of the well-aligned of moleculars,good spectral complementarity,as well as the rate of high electron and hole transfer,there are a high PCE of 9.54%has achieved which are significantly enhanced compared to the device of PBDB-T:ITIC?PCE=8.46%?.Due to the unique role of the IDDT-T-TBA and IDDT-TC6-TBA aeceptors,which cause higher V_OC,larger exciton generation and transfer.