Structure-Property Relationships of Oligothiophene-Isoindigo Polymers for Efficient Bulk-Heterojunction Solar Cells
Journal article, 2014

A series of alternating oligothiophene (nT)–isoindigo (I) copolymers (PnTI) were synthesized to investigate the influence of the oligothiophene block length on the photovoltaic (PV) properties of PnTI:PCBM bulk-heterojunction blends. Our study indicates that the number of thiophene rings (n) in the repeating unit alters both polymer crystallinity and polymer–fullerene interfacial energetics, which results in a decreasing open-circuit voltage (Voc) of the solar cells with increasing n. The short-circuit current density (Jsc) of P1TI:PCBM devices is limited by the absence of a significant driving force for electron transfer. Instead, blends based on P5TI and P6TI feature large polymer domains, which limit charge generation and thus Jsc. The best PV performance with a power conversion efficiency of up to 6.9% was achieved with devices based on P3TI, where a combination of a favorable morphology and an optimal interfacial energy level offset ensures efficient exciton separation and charge generation. The structure–property relationship demonstrated in this work would be a valuable guideline for the design of high performance polymers with small energy losses during the charge generation process, allowing for the fabrication of efficient solar cells that combine a minimal loss in Voc with a high Jsc.

Author

Z. F. Ma

Linköping University

Wenjun Sun

Chalmers, Chemical and Biological Engineering, Polymer Technology

Scott Himmelberger

Stanford University

K. Vandewal

Stanford University

Z. Tang

Linköping University

J. Bergqvist

Linköping University

Alberto Salleo

Stanford University

J. W. Andreasen

Technical University of Denmark (DTU)

Olle Inganas

Linköping University

Mats Andersson

Chalmers, Chemical and Biological Engineering, Polymer Technology

Christian Müller

Chalmers, Chemical and Biological Engineering, Polymer Technology

Fengling Zhang

Linköping University

Ergang Wang

Chalmers, Chemical and Biological Engineering, Polymer Technology

Energy and Environmental Sciences

1754-5692 (ISSN)

Vol. 7 1 361-369

Subject Categories

Polymer Chemistry

Materials Engineering

Chemical Engineering

Materials Chemistry

Nano Technology

Energy Systems

Chemical Sciences

Driving Forces

Sustainable development

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Energy

Materials Science

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

DOI

10.1039/C3EE42989J

More information

Latest update

3/6/2018 1