Quantifying and Comparing Fundamental Loss Mechanisms to Enable Solar‐to‐Hydrogen Conversion Efficiencies above 20% Using Perovskite–Silicon Tandem Absorbers

Abstract

Photovoltaic (PV)‐based solar hydrogen generation is a promising pathway for the scalable production of renewable fuels. Understanding the limitations of solar‐to‐hydrogen (STH) conversion efficiencies is critical to identify performance limits and conceptualize practical device designs. Herein, the losses in PV‐based solar hydrogen generation systems are quantified and the potential of loss‐mitigation techniques to improve the STH efficiency is assessed. The analysis shows that the two largest losses in an ideal system are current and voltage mismatches due to suboptimal system configurations and energy lost as heat in the PV component. A temperature‐dependent model is developed to evaluate the relative potential of two techniques to mitigate these losses: decoupling the PV system to remove current and voltage matching requirements and thermal integration to use the heat losses from PV to increase the electrolyte temperature and improve the reaction dynamics for water splitting. It is shown that optimal system configuration strategies provide more than three times the STH efficiency increase of thermal integration at high operating temperatures. Combining both techniques results in predicted STH efficiencies approaching 20% for low‐cost perovskite–silicon tandem‐based systems with earth‐abundant catalysts at realistic working temperatures.