Research Professor Minsu Kim (Department of Nano Convergence Engineering; BK21-FOUR Project Group for Training Talents in Nano-Convergent Energy Innovative Materials and Components), a member of the research team led by Professor Seung-hee Lee, Jeonbuk National University (JBNU) (Department of Polymer -Nano Science &Technology; Department of Nano Convergence Engineering; Dept. of JBNU-KIST Industry-Academia Convergence Research), has developed a novel photonic device technology that precisely controls light from ultraviolet to visible wavelengths using only electrical signals and can modulate the emission of quantum dots (Quantum Dot, QD) via voltage rather than current.

This study is notable for proposing a new architecture, the "QD-LCD" concept, which could overcome fundamental limitations of existing OLED-based displays.

The research team first implemented an optical platform capable of electrically switching freely between a transparent state and a scattering state by using Polymer Network Liquid Crystal (PNLC), which controls the initial alignment of liquid crystal molecules through a polymer network.

In the absence of applied voltage, the device showed high optical transparency with about 83% transmittance and low haze of approximately 1.5%. When voltage was applied, it switched to a strong scattering state with roughly 90% scattering, effectively blocking light.

This switching is not due to simple light absorption but arises from scattering caused by refractive index mismatch as the liquid crystal molecules reorient under an electric field. In addition, the device begins operating at a low voltage on the order of about 1.5 V/μm, offering advantages in energy efficiency.

The key of this study is a new approach that can control quantum dot emission without directly driving it by current. The team used PNLC as an optical shutter to voltage-control the intensity of ultraviolet or blue excitation light. By controlling the amount of excitation light reaching the quantum dots, they successfully modulated quantum dot emission intensity indirectly.

They achieved a high emission modulation ratio of up to approximately 92–97% for both green (~530 nm) and red (~630 nm) quantum dots, and confirmed fast response times on the order of milliseconds and stable repeatable operation. This is a non-contact method of emission control that does not inject current directly into the quantum dot layer, representing an important technological advance distinct from conventional methods.

Based on these results, the research team proposed the "QD-LCD" concept as a new display architecture that could replace existing QD-OLED structures. Conventional QD-OLEDs face limitations such as low efficiency of blue OLEDs, burn-in, optical losses from the use of color filters, and lifetime issues.

By contrast, the proposed architecture combines an LED backlight, a PNLC optical shutter, and a quantum dot color conversion layer, presenting the potential for higher brightness, longer lifetime, lower driving voltage, and high color purity without color filters.

This technology also has applications beyond displays, including smart windows and optical control devices. Because it can simultaneously control ultraviolet and visible regions, it can be used for smart window technologies aimed at building energy savings and improving indoor environments, and is expected to extend to adaptive optical devices and next‑generation optoelectronic systems.

Research Professor Minsu Kim emphasized, "We should pay attention to voltage‑driven technologies that can fundamentally overcome the limitations arising from current‑driven operation. By integrating liquid crystal–based optical control technology and quantum dot emission technology into a single system, we have presented a new paradigm that indirectly controls light via electrical signals, which has significant academic and industrial implications."

PhD candidates Archana Ramadas and Patekari Mangeshi participated in this study. The research was carried out with support from the Ministry of Education's BK21-FOUR Project for Training Talents in Nano-Convergent Energy Innovative Materials and Components and the National Research Foundation of Korea's Mid‑Career Researcher Support Program. The results were published in the latest issue of the internationally recognized electronics journal npj Flexible Electronics (IF=15.5, top 1.5% in the field) under the title "Electrically tunable UV–visible modulation and voltage‑controlled quantum dot emission via polymer network liquid crystals".