The Design,Synthesis And Device Characterization Of Non-fullerene Small Molecular Acceptor Materials For Organic Solar Cells

Due to the shortage of energy and pollution problem,the search for clean energy that can replace traditional fossil energy has attracted a lot attention in recent years.We can use solar energy as clean energy because it is inexhaustible.Compared with the traditional silicon-based solar cells,organic solar cells(OSCs)have a lot of advantages such as low-cost,flexible,safe and pollution-free in production.The active layer materials of OSCs consist of the donor(polymer and small molecules)and acceptor(fullerene derivatives and non-fullerene acceptor)material.Fullerene derivatives have their disadvantages such as weak absorption in the visible region,high-cost synthesis and difficulties in purification processes,hard to regulate the energy level.These disadvantages restrict their future applications.The power conversion efficiencies(PCEs)of single junction OSCs based on non-fuller^ene acceptor have reached 14%,which exceed fullerene derivatives based OSCs devices.Design and synthesis novel non-fullerene acceptor materials have been considered as the most effective method to improve PCEs of OCSs.In this dissertation,novel non-fullerene acceptors were synthesized and used as electron acceptors in OSCs.The relationship between the structure and properties of non-fullerene acceptors were studied.The detail contents are as follows:1.Two novel carbazole-cored small molecules CzC6C8 and CzC8 bearing different side chains were synthesized and used as electron acceptors in OSCs.The influence of side chains on the morphology of the blend film was studied.Device based on PBT:CzC6C8 gave the PCE of 3.30%.CzC8 bearing a linear alkyl side chain showed a better PCE of 4.61%.CzC8 based OSCs can still exhibit a good performance even though the?ELUMO and ?EHOMO between donor and acceptor are both small.Three polymer donors with a similar LUMO level but various HOMO levels were tested and they all showed good PCE values larger than 4.6%.2.Two novel non-fullerene acceptors ITIC-m-SC8 and ITIC-m-FSC8 were synthesized and used as acceptors for OSCs.Fluorine atoms were introduced onto the side chains of ITIC-m-FSC8 and the influence on morphology of the blend film and photovoltaic properties were investigated.Device based on ITIC-m-SC8 exhibited a power conversion efficiency(PCE)of 6.53%.After introducing the fluorine atom on side chains,ITIC-m-FSC8 based device gave a PCE of 7.17%.The introduction of fluorine atoms can ehance the intermolecular interaction and the self-assembly,which is benefical for charge transportation.3.Two novel non-fullerene acceptors TTIC and TTIC-M were synthesized.The core unit of TTIC and TTIC-M possess strong electron donating ability,which can broaden the absorption of the resulting acceptor molecule by enhanced internal charge transfer effect.TTIC and TTIC-M showed a broad absorption with the edge extending to the NIR region(900 nm),which can broaden the absorption of the blend film.Devices based on PBDB-T:TTIC gave a PCE of 10.61%.Devices based on PBDB-T:TTIC-M provided a higher PCE of 11.48%.11.48%is one of the best performance for polymer solar cells based on small band gap nonfullerene acceptors(<1.45 eV).