Structure–Property Relationships with Functionalized Subphthalocyanines: Toward Photovoltaic Devices More Stable to Photooxidative Degradation Mediated by Singlet Oxygen

Abstract

In this work, the overarching goal of improving the photooxidative stability of organic components used in photovoltaic devices is addressed, focusing on the common problem of degradation mediated by singlet molecular oxygen. Through a systematic exploration of boron subphthalocyanines (SubPcs), the influence of donor and acceptor substituents on the SubPc's redox properties has been examined, including the SubPc's ability to (1) act as a photosensitizer for singlet oxygen generation and (2) deactivate singlet oxygen are examined. How singlet oxygen formation and removal are influenced by linking together three SubPcs in a compact structure and by linking a SubPc to another molecular unit of relevance for organic photovoltaics (indenofluorene-extended tetrathiafulvalene) is also examined. Synthetic protocols rooted in acetylenic scaffolding, experimental and computational structure–property relationships (optical and redox properties, singlet oxygen quantum yields, and removal kinetics), and characteristics of a functional photovoltaic device using a SubPc molecule are presented, demonstrating that cyano functionalization results in remarkably enhanced organic photovoltaic device stability.