Advancing Tandem Organic Solar Cells With Ternary Acceptor Control for High‐Power Modules and Solar‐to‐Ammonia Conversion

Organic solar cells (OSCs) are emerging as a promising renewable energy technology due to their intrinsic advantages, including mechanical flexibility, lightweight, cost‐effective processing, and easy bandgap tuning. Among advanced device architectures, tandem OSCs have been extensively investigated to improve solar energy harvesting through the development of new organic semiconductors and optimized device designs. In this work, we studied solution‐processed hetero‐tandem OSCs featuring a ternary blend (PBDTTPD‐HT: PC 71 BM: IDIC) as the bottom sub‐cell and a binary blend (PTB7‐Th: o ‐IO1) as the top sub‐cell. Through morphological control of the ternary active layer and optical optimization, a power conversion efficiency (PCE) of 15.53% was achieved for tandem OSCs employing a 5:5 weight ratio of acceptors in the ternary bottom sub‐cell. Furthermore, we demonstrated a tandem OSCs mini‐module consisting of four serially connected unit tandem OSCs, which showed a PCE of 9.16% with an output voltage of 6.11 V. Finally, as a proof‐of‐concept application, the tandem OSCs were integrated into a solar‐to‐ammonia (PV‐EC) system for electricity‐driven electrolysis, achieving a solar‐to‐ammonia (STA) conversion efficiency of 4.65%.