Expanding the potential of metal halides for deep ultraviolet photodetectors

Deep-ultraviolet (DUV) photodetectors are becoming increasingly popular for applications such as environmental monitoring, secure optical communication, flame sensing, and ultraviolet imaging. Especially prized are DUVs that operate in the solar-blind region — less than 280 nanometers — for their ability to limit background solar radiation interference.

While wide-bandgap semiconductors such as gallium nitride, gallium oxide, and diamond remain the dominant material platforms, metal halides have emerged recently as promising candidates for developing DUV detectors. But achieving high photoresponse with them, as well as robust operational stability and imaging capability, remains challenging.

Zeng et al. demonstrated that a crystal composed of rubidium, copper, and iodine combines wide direct bandgap with excellent stability. They showed that the low-dimensional copper halide compound could enable sensitive solar-blind DUV photodetection, stable operation, and wavelength-selective imaging — all within a single material system.

“Our results show that low-dimensional inorganic copper halides can simultaneously deliver the key attributes required for practical DUV optoelectronic devices,” said author Wensi Cai.

The researchers used a solutions-based method to synthesize the crystals and conducted encouraging first-principles calculations. They then fabricated DUV photodetectors and tested them for photoresponse and operational stability under various conditions. They also built a wavelength-dependent UV imaging system to evaluate the imaging capability.

Finally, to study stability, the team performed imaging measurements, both after long durations and under high temperatures. All produced results with clear contours and high contrast.

“Rather than simply improving device performance, our study shows that carefully designed inorganic copper halides can serve as a complementary materials platform for deep-ultraviolet technologies,” said Cai.

Source: “Rubidium copper iodide single crystals for deep-ultraviolet detection and imaging,” by Zhongqing Zeng, Linfeng Chen, Baiqian Wang, Lunan Pei, Zhigang Zang, and Wensi Cai, Applied Physics Letters (2026). The article can be accessed at https://doi.org/10.1063/5.0347448 .