All-polymer organic solar cells with fused carbazole acceptors for indoor photovoltaics

The rapid expansion of the Internet of Things (IoT) necessitates maintenance-free, high-efficiency power sources. Organic solar cells (OSCs), offering superior spectral alignment with indoor lighting, are promising candidates for indoor energy harvesting. Here, we develop a fused carbazole-based polymer acceptor (designated as PCzT) with a tailored optical bandgap, rigid planar backbone, and enhanced electron-transporting properties. As a result, devices incorporating this acceptor achieve a power conversion efficiency of 8.15% under AM1.5G illumination and 11.63% under 3000 K, 1000 lux indoor lighting—outperforming state-of-the-art polymer acceptors in indoor applications. Crucially, we correlate nanoscale morphology (e.g., phase purity and domain size) with device performance, revealing that optimized interfacial packing enhances charge extraction and suppresses recombination. These findings provide a direct guideline for designing stable, high-performance polymer acceptors toward efficient indoor OSCs.