Quantum Dots Converted Light Emitting Diodes Packaging for Lighting and Display: Status and Perspectives

Abstract

Recent years, semiconductor quantum dots (QDs) have attracted tremendous attentions for their unique characteristics for solidstate lighting (SSL) and thinfilm display applications. The pure and tunable spectra of QDs make it possible to simultaneously achieve excellent colorrendering properties and high luminous efficiency (LE) when combining colloidal QDs with lightemitting diodes (LEDs). Due to its solutionbased synthetic route, QDs are impractical for fabrication of LED. QDs have to be incorporated into polymer matrix, and the mixture is dispensed into the LED mold or placed onto the LED to fabricate the QD–LEDs, which is known as the packaging process. In this process, the compatibility of QDs' surface ligands with the polymer matrix should be ensured, otherwise the poor compatibility can lead to agglomeration or surface damage of QDs. Besides, combination of QDs–polymer with LED chip is a key step that converts part of blue light into other wavelengths (WLs) of light, so as to generate white light in the end. Since QDLEDs consist of three or more kinds of QDs, the spectra distribution should be optimized to achieve a high colorrendering ability. This requires both theoretical spectra optimization and experimental validation. In addition, to prolong the reliability and lifetime of QDLEDs, QDs have to be protected from oxygen and moisture penetration. And the heat generation inside the package should be well controlled because high temperature results in QDs' thermal quenching, consequently deteriorates QDLEDs' performance greatly. Overall, QDLEDs' packaging and applications present the abovementioned technical challenges. A profound and comprehensive understanding of these problems enables the advancements of QDLEDs' packaging processes and designs. In this review, we summarized the recent progress in the packaging of QDLEDs. The wide applications of QDLEDs in lighting and display were overviewed, followed by the challenges and the corresponding progresses for the QDLEDs' packaging. This is a domain in which significant progress has been achieved in the last decade, and reporting on these advances will facilitate stateoftheart QDLEDs' packaging and application technologies.