Low-bandgap quinoxaline-based D-A-type copolymers: Synthesis, characterization, and photovoltaic properties

An alternating polymer with fluorinated quinoxaline and 2,7-carbazole segments for photovoltaic devices

Compared to the non-fluorinated counterpart, PCzFTQx-based device exhibited an enhanced PCE of 5.19% with corresponding high V_oc of 0.94 V.

Enhancing the power conversion efficiency of polymer solar cells via selection of quinoxaline substituents

Improvement of the power conversion efficiency of polymer solar cells was successfully achieved by selecting appropriate quinoxaline substituents on the polymer backbone.

Pyrrolo[3,4-g]quinoxaline-6,8-dione-based conjugated copolymers for bulk heterojunction solar cells with high photovoltages

D–A copolymers incorporating new pyrrolo[3,4-g]quinoxaline-6,8-dione (PQD) building blocks were synthesized for bulk heterojunction solar cells with high photovoltages.

Effects of cyano-substituents on the molecular packing structures of conjugated polymers for bulk-heterojunction solar cells

The molecular packing structures of two conjugated polymers based on alkoxy naphthalene, one with cyano-substituents and one without, have been investigated to determine the effects of electron-withdrawing cyano-groups on the performance of bulk-heterojunction solar cells. The substituted cyano-groups facilitate the self-assembly of the polymer chains, and the cyano-substituted polymer:PC71BM blend exhibits enhanced exciton dissociation to PC71BM. Moreover, the electron-withdrawing cyano-groups lower the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of the conjugated polymer, which leads to a higher open circuit voltage (V(OC)) and a lower energy loss during electron transfer from the donor to the acceptor. A bulk-heterojunction device fabricated with the cyano-substituted polymer:PC71BM blend has a higher V(OC) (0.89 V), a higher fill factor (FF) (51.4%), and a lower short circuit current (J(SC)) (7.4 mA/cm(2)) than that of the noncyano-substituted polymer:PC71BM blend under AM 1.5G illumination with an intensity of 100 mW cm(-2). Thus, the cyano-substitution of conjugated polymers may be an effective strategy for optimizing the domain size and crystallinity of the polymer:PC71BM blend, and for increasing V(OC) by tuning the HOMO and LUMO energy levels of the conjugated polymer.

In situ modulation of the vertical distribution in a blend of P3HT and PC(60)BM via the addition of a composition gradient inducer

2,2,3,3,4,4,4-Heptafluoro-N-phenyl-butyr-amide (F-ADD) was synthesized and shown to induce a composition gradient in a blend of P3HT and PC60BM. The addition of small amounts (ca. 0.5 wt%) of F-ADD modulated the chemical distribution in the blend along the vertical direction by controlling the blend component interface energy through selective interactions between F-ADD and PC60BM. A homogeneous compositional distribution along the vertical direction in the nanostructured bulk heterojunction (BHJ) increased the interfacial area, which shortened the exciton path length to the donor-acceptor interface and improved the photovoltaic performance.