Light-emitting field-effect transistors with EQE over 20% enabled by a dielectric-quantum dots-dielectric sandwich...

Emerging quantum dots (QDs) based light-emitting field-effect transistors (QLEFETs) could generate light emission with high color purity and provide facile route to tune optoelectronic properties at a low fabrication cost. Considerable efforts have been devoted to designing device structure and to understanding the underlying physics, yet the overall performance of QLEFETs remains low due to the charge/exciton loss at the interface and the large band offset of a QD layer with respect to the adjacent carrier transport layers. Here, we report highly efficient QLEFETs with an external quantum efficiency (EQE) of over 20% by employing a dielectric-QDs-dielectric (DQD) sandwich structure. Such DQD structure is used to control the carrier behavior by modulating energy band alignment, thus shifting the exciton recombination zone into the emissive layer. Also, enhanced radiative recombination is achieved by preventing the exciton loss due to presence of surface traps and the luminescence quenching induced by interfacial charge transfer. The DQD sandwiched design presents a new concept to improve the electroluminescence performance of QLEFETs, which can be transferred to other material systems and hence can facilitate exploitation of QDs in a new type of optoelectronic devices.