10% Efficient Solar-to-Hydrogen Conversion via Ternary-Phase Organic Light Absorbers With Ni Heazlewoodite Electrocatalysts

The realization of practical solar hydrogen production relies on the development of efficient devices with nontoxic and low-cost materials. Since the predominant contributors for the performance and cost are the catalyst and the light absorber, it is imperative to develop cost-effective catalysts and absorbers that are compatible with each other for achieving high performance. In this study, a 10% efficient solar-to-hydrogen conversion device was developed through the meticulous integration of low-cost Ni Heazlewoodite-based catalysts for the hydrogen evolution reaction (HER) and ternary bulk heterojunction organic semiconductor (OS)-based light absorbers. Se-incorporated Ni₃S₂ was synthesized using a simple one-step hydrothermal method, which demonstrated a low overpotential and Tafel slope, indicating superior HER activity compared to Ni₃S₂. The theoretical calculation results validate the enhanced HER performance of the Se-incorporated Ni₃S₂ catalyst in alkaline electrolytes. The ternary phase organic light absorber is designed to generate tailored photovoltage and maximized photocurrent, resulting in a photocurrent density of 8.24 mA cm⁻² under unbiased conditions, which corresponds to 10% solar to hydrogen conversion. Low-temperature photoluminescence spectroscopy results revealed that the enhanced photocurrent density originates from a reduction in both phonon- and vibration-induced inter- and intramolecular non-radiative decay. Our results establish a new benchmark for the emerging OS-based efficient solar hydrogen production based on nontoxic and cost-effective materials.