Synthesis and characterization of GaP quantum dots and their application as color converters in LEDs

Abstract

The semiconductor nanomaterials have received substantial interest in the last 20 years due to the great chemical, physical properties of them. The initial studies of this field were actively conducted about containing cadmium (Cd) and lead (Pb) group II-VI semiconductors because these nanomaterials can be easily obtained by the control of nucleation and growth steps via various synthetic methods such as the hot injection method, or heating-up process. Also, these materials have tried to be used for the various applications such as LEDs, solar cell, color conversion devices, and drug delivery. However, despite the excellent optical and chemical properties of group II-VI quantum dots (QDs), applications of group II-VI nanomaterials are limited due to the toxicity of cadmium and lead. There are active researches to solve these problems through the development of synthetic methods for the non-toxic group III-V nanomaterials. However, the studies were just focused on indium phosphide (InP) nanocrystals and the materials to replace group II-V nanomaterials still lack. In this study, we presented the first results of colloidal gallium phosphide (GaP) QDs synthesis with remarkable optical properties for applying optical devices. The colloidal GaP QDs were synthesized by using the appropriate combination of precursors. The emission wavelengths of GaP QDs were mainly controlled from 400 nm to 520 nm by the ratio of precursors to surfactants. Moreover GaP QDs presented photoluminescence quantum yield (PL QY) of 35~40% and FWHM of ~75 nm in green emission. Furthermore, the GaP QDs with green emission (520 nm) were applied as color conversion materials in color conversion device with UV LED and blue LED chips. As a result, we obtained green emission by color conversion of GaP QDs and the average color conversion efficiencies were calculated in 10~15%. The performance of devices still lacked to use single color conversion materials but that was sufficient to confirm the possibility of GaP QDs as next generation color conversion materials.