Benzobisthiadiazole-alt-bithiazole copolymers with deep HOMO levels for good-performance field-effect transistors with air stability and a high on/off ratio

Choi

Advanced Energy Materials

et al. 2017

102

A wide‐bandgap polymer, (poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(2,5‐(methyl thiophene carboxylate))]) (3MT‐Th), is synthesized to obtain a complementary broad range absorption when harmonized with 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (ITIC). The synthesized regiorandom 3MT‐Th polymer shows good solubility in nonhalogenated solvents. A film of 3MT‐Th:ITIC can be employed for forming an active layer in a polymer solar cell (PSC), with the blend solution containing toluene with 0.25% diphenylether as a nonhalogenated additive. The corresponding PSC devices display a power conversion efficiency of 9.73%. Moreover, the 3MT‐Th‐based PSCs exhibit excellent shelf‐life time of over 1000 h and are operationally stable under continuous light illumination. Therefore, methyl thiophene‐3‐carboxylate in 3MT‐Th is a promising new accepting unit for constructing p‐type polymers used for high‐performance nonfullerene‐type PSCs.

Section: Introductionmentioning

confidence: 89%

Eco‐Friendly Solvent‐Processed Fullerene‐Free Polymer Solar Cells with over 9.7% Efficiency and Long‐Term Performance Stability

Choi

Advanced Energy Materials

et al. 2017

102

Macro Chemistry & Physics

“…The HOMO energy levels of the four copolymers are all suitable for hole injection and transport . P(BBT‐20‐TET) and P(BBT‐Si‐TET) have deeper HOMO energy levels than P(BBT‐20‐TVT) and P(BBT‐Si‐TVT) due to the larger electronegativity of TET unit, implying that P(BBT‐20‐TET) and P(BBT‐Si‐TET) may have better air stability than P(BBT‐20‐TVT) and P(BBT‐Si‐TVT) . The lowest unoccupied molecular orbital (LUMO) energy levels are calculated from the onset of the reduction peaks, and their LUMO energy levels are in the range of −3.97 to −4.14 eV.…”

Section: Resultsmentioning

confidence: 99%

“…The lowest unoccupied molecular orbital (LUMO) energy levels are calculated from the onset of the reduction peaks, and their LUMO energy levels are in the range of −3.97 to −4.14 eV. The deep LUMO energy levels of the four polymers are suitable for electron injection …”

Section: Resultsmentioning

confidence: 99%

“…The HOMOs of the four copolymers are highly delocalized among the polymer backbones, and the LUMOs are mainly distributed on the BBT units. Since the more delocalized orbital distributions may induce better orbital overlap and are beneficial for intermolecular charge transport, the orbital distributions of the four copolymers are suitable for hole transport, but may inhibit electron transport …”

Section: Resultsmentioning

confidence: 99%

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Effects of Different Unsaturated‐Linker‐Containing Donors on Electronic Properties of Benzobisthiadiazole‐Based Copolymers

Zhang

Chen

Yang

et al. 2017

Self Cite

A series of new copolymers with unsaturated‐linker‐containing donors and benzobisthiadiazole acceptors are synthesized. Two kinds of side chains (2‐octyl‐1‐dodecyl chain and siloxane‐terminated hexyl chain) are added to the polymer backbone. The introduction of unsaturated‐linker‐containing donor enhances the rigidity of the copolymers. The strong electron‐withdrawing benzobisthiadiazole units make these copolymers display very narrow bandgaps in the range of 0.75–1.26 eV. Bottom‐gate and bottom‐contact transistors based on these polymers exhibit p‐type field‐effect behavior with hole mobilities up to 1.17 × 10−3 cm2 V−1 s−1.

“…In contrast, some benzoazole fused rings with stronger quinoid effects than BT and BTAZ, e.g., benzo[1,2‐ c ;4,5‐ c ′]bisthiadiazole (BBT) and [1,2,5]thiadiazolo[3,4‐ f ]benzotriazole (TBZ) owning two azole rings fused to a benzene ring, have been used successfully to construct conjugated polymers with very narrow bandgaps and high charge carrier mobilities. [ 52–56 ] Such characteristics are appealing for their photovoltaic applications. Unfortunately, to our best knowledge, efficient NFAs containing BBT and TBZ units have been rarely reported.…”

Section: Introductionmentioning

confidence: 99%

Influences of Quinoid Structures on Stability and Photovoltaic Performance of Nonfullerene Acceptors

Geng

et al. 2020

Solar RRL

Although benzoazole-fused rings with strong quinoid character have successfully been used to construct high-performance small-molecule nonfullerene acceptors (NFAs), studies into how these units influence the stabilities of NFAs and their corresponding device performances are few to date. To address it, four new NFAs, SSTI, SNTI, NTI and NTTI, which adopt BBT, TBZ, and BTAZ as the cores, respectively, are designed and investigated. It is found that SSTI and SNTI based on BBT and TBZ cores with stronger quinoid resonance effects show features of more red-shifted absorptions and deeper energy levels, but worse thermal and light stabilities than NTI and NTTI with a BTAZ core, especially in solutions and/or films blended with polymer donors. Through matrix-assisted laser desorption ionization time of flight mass spectrometry analysis of the degradation products, it is disclosed that the C═C double bond cleavage would be accelerated by stronger quinoid effects. Therefore, NTI and NTTI with relatively weaker quinoid characteristics show improved photovoltaic properties. Especially, NTTI based devices yield a good efficiency of 8.61% as the side chains on sp3-hybrid C atoms can prevent the formation of large aggregates. These findings can provide invaluable knowledge for the molecular design of NFAs with both high-efficiency and high-stability