March 04, 2026 -- A research team led by Professor Jiwoong Yang and Professor Su Il In from the Department of Energy Science & Engineering at DGIST (President Kunwoo Lee), in collaboration with Professor Jae-Yup Kim from the Department of Chemical Engineering at Konkuk University, has developed a technology to precisely control the concentration of anion defects in eco-friendly quantum dots through joint research. Through this technology, the research team achieved world-class solar hydrogen production efficiency in the field of heavy-metal-free eco-friendly quantum dot photoelectrodes.

A quantum dot is a nanoscale semiconductor crystal that is receiving attention as a key next-generation material across various fields—such as displays, optical sensors, and solar-driven hydrogen production—based on its outstanding optical and electrical properties. In particular, it holds high potential for photoelectrochemical hydrogen production technologies that convert solar energy into hydrogen fuel, but most existing high-efficiency quantum dots contain toxic heavy metals, which has limited their commercialization. Although research has been actively conducted to develop eco-friendly alternatives, their relatively low efficiency compared to heavy-metal-based materials has remained a major technical challenge.

I–III–VI group–based quantum dots, a representative class of eco-friendly quantum dots, have tended to exhibit a high density of anion defects within the crystal lattice because of their multicomponent structural characteristics, resulting in degraded optoelectronic properties. The DGIST research team developed a proprietary process that enables flexible control over the concentration of anion defects—which has been identified as a chronic weakness of eco-friendly quantum dots—through a simple yet effective strategy of finely tuning precursor ratios.

The study results confirmed that in copper–indium–sulfur–selenium (CuIn(S1-xSex)₂) quantum dots, lattice distortion is minimized when sulfur and selenium are mixed at a 1:1 ratio (CuIn(S0.5Se0.5)₂), while the concentration of anion defects is reduced to its lowest level, and crystal stability is maximized.

The defect-minimized eco-friendly quantum dots exhibited increased charge carrier concentration and prolonged lifetime, enabling photogenerated charges to migrate efficiently without recombination losses. When applied to a titanium dioxide–based (TiO₂-based) photoelectrode, they achieved a record photocurrent density of 15.1 mA·cm⁻² at 0.6 VRHE. This result demonstrates that high performance comparable to that of conventional toxic quantum dots can be realized without the use of hazardous heavy metals.

The research team secured not only high efficiency but also long-term operational stability, a key component of commercialization. By introducing a dual protective layer composed of zinc sulfide (ZnS) and silicon dioxide (SiO₂) onto the quantum dot surface, they effectively suppressed performance degradation caused by oxidative reactions in aqueous environments.

“This study represents a case in which the intrinsic defect issue—the most significant weakness of eco-friendly quantum dots—was precisely controlled through nanoscale process engineering, thereby overcoming performance limitations,” stated Professor Jiwoong Yang. “By demonstrating that high-efficiency hydrogen production is achievable without hazardous heavy metals, the findings are expected to contribute to accelerating the commercialization of sustainable, eco-friendly hydrogen energy.”

Meanwhile, this research was supported by the Ministry of Science and ICT and the National Research Foundation of Korea’s Nano and Materials Technology Development Program, as well as by the Ministry of Trade, Industry and Energy and the Korea Institute for Advancement of Technology’s International Collaborative Technology Development Program. The research findings were published online in eScience (IF 36.6), a top-tier international journal in the fields of energy and the environment. DGIST will continue to advance research aimed at leading the future hydrogen energy industry based on its technologies in eco-friendly energy materials.