The Phase Behavior of a Polymer-Fullerene Bulk Heterojunction System that Contains Bimolecular Crystals

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Entry by Yuhang Jin, AP225 Fall 2011

Reference

Nichole Cates Miller, Roman Gysel, Chad E. Miller, Eric Verploegen, Zach Beiley, Martin Heeney, Iain McCulloch, Zhenan Bao, Michael F. Toney, and Michael D. McGehee, Polym. Phys., 2011, 49, 499.

Keywords

conjugated polymers, differential scanning calorimetry (DSC), phase diagrams, X-ray

Introduction

Fig.1 Chemical structures of (A) pBTTT and (B) PC71BM.

Polymer-fullerene bulk heterojunction (BHJ) solar cells, which show promise as future energy source, consist of an interpenetrating network of an electron-donating conjugated polymer and an electron-accepting fullerene derivative. The phase behavior of these polymer-fullerene blends is very important to the optimization of solar cell performance. This paper for the first time determines the phase diagram of a polymer-fullerene blend of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene (pBTTT) with phenyl-c71-butyric acid methyl ester (PC71BM) that forms bimolecular crystals due to fullerene intercalation between the polymer side chains. The structures of pBTTT and PC71BM are shown in Fig. 1.