Abstract
To enhance the open circuit voltage (Voc) of bulk heterojunction (BHJ) polymer solar cells (PSCs) fabricated using dithieno[3,2-b:2′, 3′-d]pyrrole (DTP)-based copolymers, methyl thiophene-3-carboxylate was introduced as a weak acceptor into the polymer backbone. Two types of copolymers showed different optical and electrochemical properties even though both had an identical polymer backbone, with one of them having alkyl side chains tethered to the DTP unit. The energy level of the highest occupied molecular orbital (HOMO) of PDTPMT-C11 with a Y-branched alkyl chain was -5.22 eV, which was lower by 0.53 eV than that of PDTPMT-C12 with linear alkyl chains. The PSC, fabricated using PDTPMT-C11 and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), showed a power conversion efficiency (PCE) of 1.8% with a Voc of 0.73 V, while the PSC comprising PDTPMT-C12:PC71BM BHJ-PSC had PCE of 0.23%, which was limited by a relatively lower Voc (0.26 V) corresponding to the HOMO level (-4.69 eV) of PDTPMT-C12.
Original language | English |
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Pages (from-to) | 22-27 |
Number of pages | 6 |
Journal | Synthetic Metals |
Volume | 182 |
DOIs | |
Publication status | Published - 2013 |
Bibliographical note
Funding Information:The authors acknowledge the financial support from the Basic Science Research Program through the NRF funded by the Ministry of Education ( NRF2012R1A2A1A01008797, 20110026418 and NRF20100020209 ). M.J. Cho particularly thank for the support from a Korea University Grant (2012–2013).
Keywords
- Conjugated polymer
- Dithienopyrrole
- Organic semiconductor
- Polymer solar cells
- Thiophene-3-carboxylate
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry