The Resaerch Of A-D-D-A?Type Non-Fullerene Small Molecule Acceptors And Their Photovoltaic Properties

Acceptor-Donor-Acceptor?A-D-A?non-fullerene small molecule acceptors?NF-SMAs?have attracted increasing attention in the past few years.In the currently reported high-efficiency bulk heterojunction?BHJ?systems,in order to achieve higher short-circuit current density(J_sc)and power conversion efficiency?PCE?,the most common strategy is to blending a wide bandgap donor with a complementary narrow bandgap NF-SMA.In this paper,from the perspective of designing a new type of narrow bandgap NF-SMA,two novel structures of A-D-D-A-type NF-SMAs were designed and synthesized.The photovoltaic properties of these two A-D-D-A-type acceptors in polymer solar cells and small molecule solar cells are studied in detail.The specific research is as follows:1. Two A-D-D-A-type near-infrared NF-SMAs IDT2-DFIC and C6-IDT2-DFIC with indacenodithiophene-indacenodithiophene?IDT2?as donating core and 2-?5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene?malononitrile?2FIC?as electron withdrawing end groups,has been synthesized,and applied in polymer solar cells.Compared to IDT2-DFIC with phenylhexyl side-chain,C6-IDT2-DFIC exhibits a low optical bandgap of 1.39 e V with wide absorption range in the 450-890 nm.The PCE of C6-IDT2-DFIC-based device is 12.33%,which is higher than that of the IDT2-DFIC-based device?10.06%?.More interestingly,the J_sc of C6-IDT2-DFIC has exceeded 22m A cm^-2,which is one of the highest J_scof the non-fullerene solar cells with optoelectronic response below 900 nm.Our work provides a feasible molecular design strategy to build high-efficiency NF-SMAs.2. We selected the small molecule donor 5BDTBDD with BDT as the donor unit and BDD as the acceptor unit.All small molecule organic solar cells based on the 5 BDTBDD:C6-IDT2-DFIC system was prepared.During the optimization process,it was found that after organic solar cells are treated with thermal annealing,it has a great performance improvement compared to the device without thermal annealing.In addition,5BDTBDD:C6-IDT2-DFIC-based all small molecule solar cells have more balanced charge mobility and smoother surface morphology after thermal annealing.5 BDTBDD:C6-IDT2-DFIC-based all small molecule organic solar cells show high PCE of 7.19%and FF of 69.75%after thermal annealing,while the deviceshow PCE only of 1.92%and FF of 33.03%without thermal annealing.Our work provides a feasible device optimization strategy for building efficient all small molecule organic solar cells.