Pyrrolo 3,4-g quinoxaline-6,8-dione-based conjugated copolymers for bulk heterojunction solar cells with high photovoltages
Artikel i vetenskaplig tidskrift, 2015

A new electron-deficient building block 5,9-di(thiophen-2-yl)-6H-pyrrolo[3,4-g]quinoxaline-6,8(7H)-dione (PQD) was synthesized via functionalizing the 6- and 7-positions of quinoxaline (Qx) with a dicarboxylic imide moiety. Side chain substitution on the PQD unit leads to good solubility which enables very high molecular weight copolymers to be attained. The fusion of two strong electron-withdrawing groups (Qx and dicarboxylic imide) makes the PQD unit a stronger electron-deficient moiety than if the unit had just one electron-withdrawing group, thus enhancing the intramolecular charge transfer between electron-rich and deficient units of the copolymer. Four PQD-based polymers were synthesized which feature deep-lying highest occupied molecular orbital (HOMO) levels and bathochromic absorption spectra when compared to PBDT-Qx and PBDT-TPD analogues. The copolymers incorporated with benzo[1,2-b:4,5-b']dithiophene (BDT) units show that the 1D and 2D structural variations of the side groups on the BDT unit are correlated with the device performance. As a result, the corresponding solar cells (ITO/PEDOT:PSS/polymer: PC71BM/LiF/Al) based on the four copolymers feature very high open-circuit voltages (V-oc) of around 1.0 V. The copolymer PBDT-PQD1 attains the best power conversion efficiency of 4.9%, owing to its relatively high absorption intensity and suitable film morphology. The structure-property correlation demonstrates that the new PQD unit is a promising electron-deficient building block for efficient photovoltaic materials with high V-oc.

Författare

Xiaofeng Xu

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Polymerteknologi

C. F. Wang

Linköpings universitet

Olof Bäcke

Chalmers University of Technology

David James

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Polymerteknologi

Kim Bini

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Polymerteknologi

Eva Olsson

Chalmers University of Technology

Mats Andersson

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Polymerteknologi

M. Fahlman

Linköpings universitet

Ergang Wang

Chalmers, Kemi och kemiteknik, Tillämpad kemi, Polymerteknologi

Polymer Chemistry

1759-9954 (ISSN) 1759-9962 (eISSN)

Vol. 6 4624-4633

Ämneskategorier

Polymerkemi

DOI

10.1039/c5py00394f