High-Crystalline Medium-Band-Gap Polymers Consisting of Benzodithiophene and Benzotriazole Derivatives for Organic Photovoltaic Cells

Two semiconducting conjugated polymers were synthesized via Stille polymerization. The structures combined unsubstituted or (triisopropylsilyl)ethynyl (TIPS)-substituted 2,6-bis(trimethylstannyl)benzo[1,2-b:4.5-b′]dithiophene (BDT) as a donor unit and benzotriazole with a symmetrically branched alky...

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Bibliographic Details
Published in:ACS applied materials & interfaces 2013-12, Vol.5 (24), p.12820-12831
Main Authors: Kim, Ji-Hoon, Song, Chang Eun, Shin, Nara, Kang, Hyunbum, Wood, Sebastian, Kang, In-Nam, Kim, Bumjoon J, Kim, BongSoo, Kim, Ji-Seon, Shin, Won Suk, Hwang, Do-Hoon
Format: Article
Language:English
Subjects:
Electrochemical Techniques
Fullerenes - chemistry
Polymers - chemistry
Polystyrenes - chemistry
Quantum Theory
Solar Energy
Spectrum Analysis, Raman
Thiophenes - chemistry
Tin Compounds - chemistry
Triazoles - chemistry
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Summary:Two semiconducting conjugated polymers were synthesized via Stille polymerization. The structures combined unsubstituted or (triisopropylsilyl)ethynyl (TIPS)-substituted 2,6-bis(trimethylstannyl)benzo[1,2-b:4.5-b′]dithiophene (BDT) as a donor unit and benzotriazole with a symmetrically branched alkyl side chain (DTBTz) as an acceptor unit. We investigated the effects of the different BDT moieties on the optical, electrochemical, and photovoltaic properties of the polymers and the film crystallinities and carrier mobilities. The optical-band-gap energies were measured to be 1.97 and 1.95 eV for PBDT-DTBTz and PTIPSBDT-DTBTz, respectively. Bulk heterojunction photovoltaic devices were fabricated and power conversion efficiencies of 5.5% and 2.9% were found for the PTIPSBDT-DTBTz- and PBDT-DTBTz-based devices, respectively. This difference was explained by the more optimal morphology and higher carrier mobility in the PTIPSBDT-DTBTz-based devices. This work demonstrates that, under the appropriate processing conditions, TIPS groups can change the molecular ordering and lower the highest occupied molecular orbital level, providing the potential for improved solar cell performance.
ISSN:1944-8244
1944-8252
DOI:10.1021/am401926h