High-performance quantum dot light-emitting diodes (QLEDs) are being considered as a next-generation technology for energy efficient solid-state lighting and displays. InP QLEDs are the most promising alternative to the toxic CdSe QLEDs. Unlike the problems of poor hole injection in CdSe-based QLEDs, highly delocalized electrons and parasitic emissions are serious problems in green-emitting InP QLEDs. The loss mechanism and device physics in InP QLEDs have not been sufficiently studied since the first report of InP QLED in 2011. This Focus Review summarizes the recent efforts on improving the performance of InP QLEDs from the perspectives of core/shell structures to optimization of carrier transport layers. It is our intention to conduct a review as well as clarify some previous misunderstandings regarding the device physics in InP QLEDs and to provide some insights for the possible solutions to the challenging problems in InP QLEDs.

As the concerns about using cadmium-based quantum dots (QDs) in display are growing worldwide, InP QDs have drawn much attention in quantum dot light-emitting diodes (QLEDs). However, pure blue InP based QLED has been rarely reported. In this work, first of all, pure blue InP/ZnS QDs with emission wavelength of 468 nm and quantum yield of 45% are synthesized. Furthermore, zinc oleate and STOP are used as precursors to epitaxially grow the second ZnS shell. The residual zinc stearate reacted with STOP to form ZnS shell, which increased the thickness and stability of QDs. Moreover, as the residual precursor of zinc stearate is removed, the current density increased from 13 mA cm −2 to 121 mA cm −2 at 8 V for the hole only device. External quantum efficiency increased from 0.6% of InP/ZnS QLED to 1.7% of InP/ZnS/ZnS QLED.

InP quantum dots (QDs) are emerging as promising materials for replacing cadmium‐based QDs in view of their heavy metal‐free and tunable luminescence. However, the development of InP QD materials still lags due to the expensive and flammable phosphorus precursors, and also the unsatisfactory repeatability caused by the fast nucleation rate. Adopting lowly reactive P precursor aminophosphine can overcome this issue, but their low photoluminescence quantum yield (PLQY) and widening line widths do not apply to the practical application. Through engineering, the core‐shell structure of QD, significantly promoted green emissions of QDs were obtained with PLQY of 95% and full width and half maximum (FWHM) of 45 nm, which demonstrated the highest PLQY record obtained from the aminophosphine system. Moreover, due to the residue halogen atoms on the QD surface as inorganic ligands to prevent further oxidization, these InP QDs demonstrated the ultra‐long operational lifetime (over 1000 h) for QDs based color enhancement film. By optimizing the device structure, an inverted green InP quantum dot light‐emitting diode (QLED) with external quantum efficiency (EQE) of 7.06% was also demonstrated, which showed a significant promise of these InP QDs in highly effective optoelectronic devices.

Copper indium sulfide colloidal quantum dots (CuInS2 QDs) have drawn lots of attention in recent years, due to their traits of nontoxic elements, low synthesis cost, and easily tunable bandgap....