All‐polymer solar cells (all‐PSCs) have attracted immense attention in recent years due to their advantages of tunable absorption spectra and electronic energy levels for both donor and acceptor polymers, as well as their superior thermal and mechanical stability. The exploration of the novel n‐type conjugated polymers (CPs), especially based on aromatic diimide (ADI), plays a vital role in the further improvement of power conversion efficiency (PCE) of all‐PSCs. Here, recent progress in structure modification of ADIs including naphthalene diimide (NDI), perylene diimide (PDI), and corresponding derivatives is reviewed, and the structure–property relationships of ADI‐based CPs are revealed.

A novel A 2 −A 1 −D−A 1 −A 2 -type nonfullerene acceptor, using thiazolidine-2,4-dione (TD) as the terminal acceptor (A 2 ) for the first time, was designed and synthesized. The final molecule, BTA2, shows a high-lying lowest unoccupied molecular orbital (LUMO) of −3.38 eV and a wide optical band gap of 2.00 eV. Fullerene-free organic solar cells based on P3HT:BTA2 realized a high open-circuit voltage (V oc ) of 1.22 V with a power conversion efficiency (PCE) of 4.50%. These values are significantly higher than those of the PC 61 BM-based control device (V oc = 0.61 V, PCE = 3.67%), which indicates the feasibility of thiazolidine-2,4-dione to construct nonfullerene small-molecule acceptors with high V oc and PCE.

No abstract

No abstract

Two polymeric electron acceptors (PFPDI-2T and PFPDI-2FT) based on the fused perylene diimide (PDI) and bithiophene or difluorobithiophene units were synthesized via the Stille polymerization. Both polymers exhibit the strong absorption between 350 and 650 nm, which have the good absorption compensation with the low band gap conjugated polymer in polymer solar cells (PSCs). PFPDI-2T and PFPDI-2FT have the LUMO energy levels of around −4.12 to −4.15 eV, which are comparable with other PDI-based polymers and fullerene derivatives. All-polymer solar cells (all-PSCs) based on PFPDI-2T or PFPDI-2FT as the polymeric electron acceptor were fabricated with PTB7-Th as the polymeric electron donor. Power conversion efficiency of as high as 6.39% based on PFPDI-2T/PTB7-Th was achieved under the standard illumination of simulated sunlight (AM 1.5, 100 mW cm −2 ), which is significant higher than that of the all-PSC based on the nonfused PDI counterpart. The results demonstrate that the direct fusion of PDI unit is an effective design strategy to enhance the photovoltaic performances of all-PSCs.

Two novel acceptor–acceptor (A–A) type polymeric electron acceptors, PPDI-DTBT and PFPDI-DTBT, which contain perylene diimide (PDI) and fused PDI (FPDI) with electron deficient 4,7-dithienyl-2,1,3-benzothiadiazole (DTBT) units, respectively, are designed and synthesized to investigate their application in all-polymer solar cells (all-PSCs).

Three quinoxaline-based "D−π−A" conjugated polymers, named as PE61, PE62, and PE63, are utilized to investigate the effect of introducing fluorine and sulfur atoms into the thiophene side chains on the photovoltaic performance when paired with a nonfullerene Y6. The open-circuit voltage (V OC ) and power conversion efficiency (PCE) can be improved from 0.66 V and 8.61% for PE61:Y6 to 0.78 V and 12.02% for PE62:Y6, and then to 0.83 V and 13.10% for PE63:Y6, respectively. The results provide a simple and effective strategy to fine-tune the optoelectronic properties and thus improve the photovoltaic performance.

No abstract