Synthesis of Block Copolymers Containing Polythiophene Segments and Their Application to Organic Photovoltaics

Polythiophenes have so far been in the best class of balanced high-performance materials as a p-type semiconductor among all pi-conjugated polymers in terms of solubility, chemical stability, charge mobility, and commercial availability. Therefore, very much attention has been paid to these materials for prompt application to polymer electronic devices, such as organic field-effect transistors and photovoltaic cells. Recently the controlled polymerization has been achieved via Grignard metathesis polymerization in a chain-growth manner to synthesize well-defined poly(3-alkylthiophene)s with predictable molecular weight, narrow molecular weight distribution, and high regioregularity. This strategy allows synthesizing a variety of block copolymers and they show unique phase separation, induced by block conformation as well as crystalline structure of polythiophene segments. This review article describes synthesis, morphology, and organic photovoltaic characteristics of polythiophene-based block copolymers in detail. Especially, the utility of block copolymers as compatibilizers in organic photovoltaics has been discussed.