Unconventional formation of dual-colored InP quantum dot-embedded silica composites for an operation-stable white light-emitting diode

Abstract

In the fabrication of color-conversion-based quantum dot-light-emitting diodes (QD-LEDs), the on-chip type is the most cost-effective, processing-convenient configuration and thus should replace well-developed but costly on-surface ones. To render on-chip QD-LEDs viable, however, the encapsulation of QDs with chemically stable species should additionally precede fabrication to prevent substantial QD degradation occurring under LED driving accompanied by high temperature and intense photon flux. For this, we explore an unconventional but simple formation of silica composites embedded with technologically important but relatively delicate non-Cd InP QDs, where a sol-gel reaction proceeds in a catalyst-free, waterless manner with a silane precursor of (3-aminopropyl)trimethoxysilane (APTMS). This ATPMS-based silica reaction is attempted first with green InP QDs with a multi-shell structure of a composition-gradient ZnSeS intermediate shell plus a ZnS outer shell, showing that it enables excellent retention of the original photoluminescence of pristine QDs as well as uniform formation of QD-silica composites. Subsequently, two InP/ZnSeS/ZnS QDs of green and red emission are co-reacted in the silica reaction to yield dual color-capable QD-silica composites. These single- and dual-colored QD-silica composites are combined as color-converters with a blue LED in an on-chip configuration. The device stability of bicolored and tricolored QD-LEDs fabricated as such is then evaluated under continuous operation at 60 mA for an extended period of time, leading to the outstanding retention of initial QD emission as high as 93-94% even after 100 h-operation and clearly validating the effectiveness of the present silica embedding on QD passivation against a harsh LED driving environment.