Semiconducting Copolymers Based on meso-Substituted BODIPY for Inverted Organic Solar Cells and Field-Effect Transistors

Abstract

The synthesis, physicochemical, and optoelectronic properties of a new class of low band‐gap (≈1.3 eV) donor–acceptor copolymers based on a highly electron‐deficient meso‐5‐(2‐octyldodecyl)thiophene‐substituted BODIPY π‐unit are presented. The polymeric solutions exhibit strong aggregation‐dependent excitonic properties indicating the presence of enhanced π‐coherence as a result of strong interchain interactions. The polymeric semiconductor thin films prepared by spin coating show isotropic nodule‐like grains with essentially no ordering in the out‐of‐plane direction. Field‐effect hole mobilities of 0.005 cm2 V−1·s−1 are observed in bottom‐gate top‐contact organic field‐effect transistors, and inverted bulk‐heterojunction organic photovoltaics employing the polymer:PC71BM active layer exhibit excellent power conversion efficiencies of 6.2% with a short‐circuit current of 16.6 mA cm−2. As far as it is known, this is a record high value achieved to date for a boron‐containing donor polymer in the photovoltaic literature indicating a significant enhancement in power conversion efficiency (>3–4 times). The findings clearly present that rationally designed BODIPY‐based donor–acceptor copolymers can be a key player in photovoltaic applications.