Conformational Disorder Enhances Solubility and Photovoltaic Performance of a Thiophene–Quinoxaline Copolymer
Artikel i vetenskaplig tidskrift, 2013

The side-chain architecture of alternating copolymers based on thiophene and quinoxaline (TQ) is found to strongly influence the solubility and photovoltaic performance. In particular, TQ polymers with different linear or branched alkyloxy-phenyl side chains on the quinoxaline unit are compared. Attaching the linear alkyloxy side-chain segment at the meta- instead of the para-position of the phenyl ring reduces the planarity of the backbone as well as the ability to order. However, the delocalisation across the backbone is not affected, which permits the design of high-performance TQ polymers that do not aggregate in solution. The use of branched meta-(2-ethylhexyl)oxy-phenyl side-chains results in a TQ polymer with an intermediate degree of order. The reduced tendency for aggregation of TQ polymers with linear meta-alkyloxy-phenyl persists in the solid state. As a result, it is possible to avoid the decrease in charge-transfer state energy that is observed for bulk-heterojunction blends of more ordered TQ polymers and fullerenes. The associated gain in open-circuit voltage of disordered TQ:fullerene solar cells, accompanied by a higher short-circuit current density, leads to a higher power conversion efficiency overall. Thus, in contrast to other donor polymers, for TQ polymers there is no need to compromise between solubility and photovoltaic performance.

Solubility

Polymer solar cell

Side-chain geometry

Thiophene-quinoxaline copolymer

Charge-transfer state

Backbone twisting

Författare

Ergang Wang

Chalmers, Kemi- och bioteknik, Polymerteknologi

J. Bergqvist

Linköpings universitet

K. Vandewal

Stanford University

Linköpings universitet

Z. F. Ma

Linköpings universitet

Lintao Hou

Linköpings universitet

Angelica Lundin

Chalmers, Kemi- och bioteknik, Polymerteknologi

Scott Himmelberger

Stanford University

Alberto Salleo

Stanford University

Christian Müller

Chalmers, Kemi- och bioteknik, Polymerteknologi

Olle Inganäs

Linköpings universitet

Fengling Zhang

Linköpings universitet

Mats Andersson

Chalmers, Kemi- och bioteknik, Polymerteknologi

Advanced Energy Materials

1614-6832 (ISSN) 1614-6840 (eISSN)

Vol. 3 806-814

Ämneskategorier

Polymerkemi

DOI

10.1002/aenm.201201019