Efficient and bright green InP quantum dot light-emitting diodes enabled by a self-assembled dipole interface monolayer

The interfacial state between the hole transport layer (HTL) and quantum dots (QDs) plays a crucial role in the optoelectronic performance of light-emitting diodes. Herein, we reported an efficient and bright green indium phosphide (InP) QD-based light-emitting diode (LED) by introducing a self-assembled monolayer of 4-bromo-2-fluorothiophenol (SAM-BFTP) molecule to improve interfacial charge transport in LED devices. The molecular dipole layer at the interface of the QD layer and HTL not only reduces the energy barrier of holes injected into QDs through vacuum energy level shift but also inhibits the fluorescence quenching of QDs caused by the HTL. Moreover, copper ions doped into phosphomolybdic acid (Cu:PMA) is selected as the hole injection layer (HIL) into the device system based on the SAM-BFTP molecule, and as a result, a green InP QD LED (QLED) with a maximum external quantum efficiency (EQE) of 8.46% and a luminance of 18 356 cd m(-2) was realized. This work can inform and underpin the future development of InP-based QLEDs with concurrent high efficiency and brightness.

Automated summary

In this study, an efficient and bright green indium phosphide (InP) quantum dot-based light-emitting diode (LED) was achieved by improving the charge transport at the interface through the introduction of a self-assembled monolayer of 4-bromo-2-fluorothiophenol (SAM-BFTP) molecule. The molecular dipole layer reduced the energy barrier of hole injection and suppressed fluorescence quenching. Copper ions doped into phosphomolybdic acid (Cu:PMA) were used as the hole injection layer (HIL), leading to a green InP quantum dot LED with a maximum external quantum efficiency (EQE) of 8.46% and a luminance of 18,356 cd/m2. This work is significant for the future development of high-efficiency and high-brightness InP-based quantum dot LEDs.