A Review on Development of Covalently Connected Donor-Acceptor Molecular Materials for Single-Component Organic Solar Cells

Abstract

Organic solar cells (OSCs) have achieved remarkable progress, with power conversion efficiencies (PCEs) surpassing 19-20 %, driven by the development of polymeric electron donors and non-fullerene acceptors (NFAs) in bulk-heterojunction (BHJ) architectures. BHJ OSCs, which rely on physical blending of donor (D) and acceptor (A) materials, face significant challenges in maintaining long-term stability. This instability limits the commercial viability of BHJ OSCs despite advancements in optimizing their morphology and device architecture. Single-component organic solar cells (SCOSCs) have emerged as a promising alternative to address these stability challenges. By covalently linking D and A units into a single molecule. These single-material devices combine the advantages of light absorption and charge transport within a unified structure, eliminating complex interfacial layers and mitigating phase-separation issues inherent in BHJ systems. To date, SCOSCs have reached a maximum power conversion efficiency (PCE) of 15%, marking notable progress toward bridging the performance gap with BHJ devices. This review highlights the structural advancements in SCOSCs, with a particular emphasis on molecular dyads, D-A double cable polymers and conjugated block copolymers and their photovoltaic performance. Furthermore, it discusses potential strategies for future innovations to improve the efficiency and scalability of SCOSCs.