Finely controlled luminescent Ag-In-Ga-S quantum dots with dual green and red emission towards white LEDs

Semiconductor quantum dot (QD) materials have shown great potential for applications in lighting and display fields due to their wide color gamut, tunable emission wavelength, high quantum efficiency, high chroma, and low processing cost. For example, quantum dot materials based on cadmium and perovskites have made remarkable progress, but further applications are limited by the use of toxic cadmium and lead.

The Restriction of Hazardous Substances (RoHS) regulations specifically limit the use of Cd and Pb in electronic products to less than 100 ppm and 1,000 ppm, respectively. Therefore, it is of great importance to develop new environmentally friendly quantum dot material systems.

In recent years, environmentally friendly I-III-VI2 QDs such as Ag-In-Ga-S (AIGS) QDs have attracted widespread attention due to their large Stokes shift, controllable emission across the visible spectrum, and high photoluminescence. Masu. Quantum Yield (PLQY).

It has great potential in the fields of lighting and displays. Due to the diverse elemental composition of AIGS, they typically exhibit broad emission spectra in the visible region, with strong bandgap main emission peaks and weak defect emission peaks.

Currently, researchers mainly focus on narrowing the PL spectrum through core-shell structures or alloying to meet display requirements. However, the dual-emission properties of quantum dots with a broad spectrum in white light applications have clear advantages, enabling the realization of single-material white light-emitting devices (WLEDs) that require complex processing, self-absorption, and degradation. disadvantages such as this are avoided. Color rendering properties of multiple fluorescent powder composite white light.

Therefore, optimizing the broad-spectrum properties of AIGS QDs and achieving fine spectral tuning is important to study the emission properties of AIGS and realize high-quality WLEDs.

Based on this, Professor Song Jizhong of Zhengzhou University took advantage of the size-dependent quantum confinement properties of quantum dot materials to control the size distribution of quantum dot crystals by controlling the temperature of nucleation and growth of AIGS quantum dots. Adjusted the size distribution of quantum dots. We achieved AIGS QDs with an emission spectrum and dual emission characteristics of green and red. The paper will be published in the journal Opto-Electronic Advances.

In this study, AIGS QDs were synthesized by one-pot thermal injection method, and the crystal size was controlled by temperature control.

At lower temperatures (180 °C), smaller particles (size 3.7 nm) formed more easily, whereas at higher temperatures (250 °C), crystals (size 16.5 nm) tended to grow. At 220 °C, AIGS QDs with two different size distributions (17 nm and 3.7 nm) were obtained, resulting in large differences in the exciton emission peaks.

Finally, AIGS QDs with dual green and red emission (530 nm to 630 nm) were achieved, and the dual-peak exciton emission properties were confirmed by temperature-dependent and excitation-dependent spectroscopy. This study provides a new perspective to study the luminescent properties of new AIGS QD material systems.

This broadband bimodal emitting QD has great potential in WLEDs. In this study, AIGS QDs with green and red dual emission were mixed with polymer, pressed into a film, and combined with a blue LED chip to successfully prepare WLEDs with chromaticity coordinates. (0.33, 0.31), Correlated Color Temperature (CCT) of 5,425 K, Color Rendering Index (CRI) of 90, and Radioluminous Efficiency (LER) of 129 lm/W, which shows that AIGS QDs have great potential. is shown. For lighting purposes.