Aug 01, 2025

Flexible optoelectronics made efficient with low-temperature hydrogen process

Scientists developed flexible optoelectronic device using low-temperature process with minimized thin-film defects via hydrogen dilution control.

(Nanowerk News) Dr. Jung-Dae Kwon's research team at the Energy & Environmental Materials Research Division of the Korea Institute of Materials Science (KIMS) has successfully developed an amorphous silicon optoelectronic device with minimal defects, even using a low-temperature process at 90°C. Notably, the team overcame the limitations of high-temperature processing by precisely controlling the hydrogen dilution ratio—the ratio of hydrogen to silane (SiH₄) gas—enabling the fabrication of high-performance flexible optoelectronic devices (sensors that detect light and convert it into electrical signals).

The findings are published in Advanced Science ("Tailoring Hydrogenation to Enhance Defect Suppression and Charge Transport in Hydrogenated Amorphous Silicon for Flexible Photodetectors").

Optoelectronic Device Fabricated on a Flexible Substrate and Its Cross-Sectional Structure. (Image: KIMS)

Flexible optoelectronic devices are key components of next-generation electronic devices, such as wearable electronics and image sensors, and require the precise deposition of thin films on thin, bendable substrates. However, a major limitation has been the necessity of high-temperature processing above 250°C, making it difficult to apply these devices to heat-sensitive flexible substrates.

To overcome this limitation, the research team employed precise control of the hydrogen dilution ratio using mass flow controllers during the plasma-enhanced chemical vapor deposition (PECVD) process, which is commonly used for thin-film device fabrication. This approach enabled uniform thin-film quality even at low temperatures. In addition, by applying hydrogen passivation, they enhanced the electrical performance of the material while minimizing thin-film defects. As a result, they succeeded in fabricating a flexible optoelectronic device that maintained its performance while reducing the processing temperature by more than 60% compared to conventional methods—significantly lowering production costs.

This technology utilizes photoresist (PR) as a sacrificial layer to enable the clean and precise formation of active areas in optoelectronic devices. Photoresist allows stable thin-film deposition even on heat-sensitive flexible substrates and can be easily removed through a simple process, thereby streamlining and improving the efficiency of the entire fabrication process. One of the key advantages of this research outcome is the ability to reliably produce high-quality optoelectronic devices without the need for complex plasma etching processes.

Using this technology, the research team achieved a high photosensitivity-approximately 96% of that of conventional high-temperature processed devices. Furthermore, after conducting over 2,700 bending tests at a 5 mm bending radius, the device demonstrated excellent mechanical durability and stability with no performance degradation. This technology is expected to be widely applicable in the fabrication of wearable and flexible electronic devices.

Dr. Jung-Dae Kwon, the principal investigator at KIMS, stated, “This technology demonstrates the potential to fabricate high-quality thin films and high-performance optoelectronic devices without high-temperature processing, simply by precisely controlling the hydrogen dilution ratio.” He added, “We expect this advancement will enable the development of cost-effective and high-performance flexible optoelectronic devices across various applications, including wearable electronics, image sensors, and optical sensors.”

Source: Korea Institute of Materials Science (Note: Content may be edited for style and length)