Bias‐Free Solar‐to‐Hydrogen Conversion in a BiVO4/PM6:Y6 Compact Tandem with Optically Balanced Light Absorption

• Published in: Energy & environmental materials (Hoboken, N.J.) Vol. 7; no. 4
• Main Authors: Ferreira, Catarina G., Sansierra, Constanza, Bernal‐Texca, Francisco, Zhang, Mingyu, Ros, Carles, Martorell, Jordi
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.07.2024
• Subjects: Absorption; Bias; Bismuth oxides; bismuth vanadate; Chemical energy; compact tandem; Electromagnetic absorption; High voltage; Multilayers; Optimization; organic solar cells; Photoanodes; Photoelectrochemical devices; Photoelectrochemistry; Photonic band gaps; photonic multilayers; Photovoltaic cells; Solar cells; solar‐to‐hydrogen conversion; Sunlight; Vanadates; Water splitting
• ISSN: 2575-0356; 2575-0356
• DOI: 10.1002/eem2.12679

The high voltage required to overcome the thermodynamic threshold and the complicated kinetics of the water splitting reaction limit the efficiency of single semiconductor‐based photoelectrochemistry. A semiconductor/solar cell tandem structure has been theoretically demonstrated as a viable path to achieve an efficient direct transformation of sunlight into chemical energy. However, compact designs exhibiting the indispensable optimally balanced light absorption have not been demonstrated. In the current work, we design and implement a compact tandem providing the complementary absorption of a highly transparent BiVO4 photoanode and a PM6:Y6 solar cell. Such bandgap combination approaches the optimal to reach the solar‐to‐hydrogen (STH) conversion upper limit for tandem photoelectrochemical cells (PECs). We demonstrate that, by using a photonic multilayer structure to adequately balance sunlight absorption among both tandem materials, a 25% increase in the bias‐free STH conversion can be achieved, setting a clear path to take compact tandem PECs to the theoretical limit performance. This work presents a route to achieve maximal solar‐to‐hydrogen conversion efficiency in tandem photoelectrochemical devices for solar‐assisted water splitting, by combining absorbing materials with complementary absorption profiles and optimal bandgap energies. The introduction of a multilayer structure optimized by an inverse design approach to balance light absorption plays a key role to reach such efficiency limit.