Fullerene-grafted block copolymers used as compatibilizer in P3HT/PCBM bulk heterojunctions: morphology and photovoltaic performances

¹ Institut d’Électronique du Solide et des Systèmes (InESS), Université de Strasbourg, CNRS, 23 rue du Loess, 67037 Strasbourg, France
² Laboratoire de Chimie des Polymères Organiques, École Nationale Supérieure de Chimie, de Biologie et de Physique, Université Bordeaux 1, 16 avenue Pey-Berland, 33607 Pessac, France
³ Department Science and Analysis of Materials, Public Research Centre Gabriel Lippmann, 41 rue du Brill, 4422 Belvaux, Luxembourg
⁴ Laboratoire d’Ingénierie des Polymères pour les Hautes Technologies (LIPHT), École Européenne de Chimie des Polymères et Matériaux (ECPM), 25 rue Becquerel, 67087 Strasbourg, France

^a e-mail: thomas.heiser@unistra.fr
^b e-mail: hadzii@enscbp.fr

Received: 13 April 2011
Revised: 12 August 2011
Accepted: 14 September 2011
Published online: 23 November 2011

Abstract

The nanostructure of the active layer in polymer/fullerene bulk heterojunction solar cells is known to have a strong impact on the device performances. Controlling the polymer/fullerene blend morphology is therefore particularly important. In this work, a rod-coil block copolymer, based on a regioregular poly(3-hexylthiophene) electron-donor rod block and a C₆₀-grafted coil block, is used as compatibilizer and its influences on the thin film morphology as well as the photovoltaic performances are investigated. It is shown that a small fraction of compatibilizer can enhance the device performances in an otherwise non-optimized process. At higher fractions or long annealing times however, the fullerene-grafted copolymer is found to behave as a nucleation center and triggers the formation of fullerene crystals.