Synthesis of emission tunable AgInS₂/ZnS quantum dots and application for light emitting diodes

Abstract

Indium-rich environmentally-friendly quantum dots (QDs) have received widespread attention due to the absence of cadmium. In this paper, AgInS 2 (AIS) QDs are synthesized by hot injection method. By adjusting the ratio of indium/silver (In/Ag=1, 2, 3, 4, 5), the AIS QDs exhibit a blue shift from 868 nm to 603 nm with the indium composition increases. Therein, the AIS QDs with the ratio of In/Ag=4 show a highest photoluminescent (PL) quantum yields (QYs) up to 57%. AIS QDs are coated with ZnS shell to passivate the surface defects, and the PL QYs of obtained core/shell AIS/ZnS QDs is increased to 72%. By using these AIS/ZnS QDs as light emitters, light emitting diodes are assembled with a stacked multi-layer structure ITO/PEDOT:PSS/Poly-TPD/QDs/ZnO:Mg/Al. The resulted electroluminescent (EL) device exhibits a maximum external quantum efficiency (EQE) of 1.25% and an open circuit voltage of 4.6 V corresponding to a maximum brightness of 1120 cd m −2 . Although the performances of the as fabricated AIS/ZnS-based device lag much behind than those of the Cd-based ones, they are expected to be enhanced with much more studies on the synthesis of the QDs and the optimization of device structure.

Luminescent Quaternary Ag(InxGa1–x)S2/GaSy Core/Shell Quantum Dots Prepared Using Dithiocarbamate Compounds and Photoluminescence Recovery via Post Treatment

“…Semiconductor quantum dots (QDs), which have been found to attract photoluminescent materials, have recently been utilized for commercial devices in terms of, for example, the color conversion material for the backlight sources used in liquid crystalline displays. − The QDs exhibit unique characteristics such as high absorption as well as a narrowband and tunable photoluminescence (PL) due to the energy band structure. In addition, the use of QDs as the emitting layer of electroluminescence devices also presents a promising application of these materials. − In the early stage of development, most of the research on QDs was focused on cadmium chalcogenide (II–VI semiconductors). However, the demand for environmentally benign alternatives as the next generation of light-emitting materials has continued to increase.…”

Integration of ternary I-III-VI quantum dots in light-emitting diodes

“…Wei et al ( Wei et al, 2020 ) obtained AgInS 2 /ZnS TQDs that exhibited a tunable emission wavelength and high QYs values (72%). The AgInS 2 TQDs were synthesized by a hot-injection strategy and coated with a ZnS layer.…”

“…The ZnS shell is able to enhance the Frontiers in Chemistry frontiersin.org QY of CuInS 2 from 3.2% to 81%, according to Chuang et al (Chuang et al, 2014). Wei et al (Wei et al, 2020) described an increase in the QY of AgInS 2 from 57% to 72% by adding a ZnS shell. Table 1 depicts QY values of different TQDs, and it is wellknown that QY values are higher when an organic solvent is used.…”

“…The ZnS shell is able to enhance the QY of CuInS 2 from 3.2% to 81%, according to Chuang et al ( Chuang et al, 2014 ). Wei et al ( Wei et al, 2020 ) described an increase in the QY of AgInS 2 from 57% to 72% by adding a ZnS shell.…”

Assessing the influence of microwave-assisted synthesis parameters and stabilizing ligands on the optical properties of AIS/ZnS quantum dots

“…Therefore, with the increasing pressure to develop and apply greener chemistry principles and safe-by-design approaches for nanomaterials, in the last years, researchers started to focus on alternatives for these QDs, which still possess comparably beneficial optical properties such as high PL QY values but are heavy-metal free. This has triggered the interest in InP 13 , carbon dots 14 , 15 , silicon QDs 16 as well as ternary QDs like CuInS 2 (CIS) and AgInS 2 (AIS) or quaternary QDs like AgInSZn (AISZ) and ZnCuInS (ZCIS) with PL in the visible and near infrared (NIR) region 17 . In contrast to binary QDs such as II/VI, IV/IV, and III/V QDs, where the optical properties are solely controlled by the width of the band gap, the PL properties of ternary QDs are ascribed to defect states in the band gap structure 18 .…”