Achieving high performance InP quantum dot light-emitting devices by using inkjet printing

InP quantum dots (QDs) are considered to be one of the most promising materials for application in light-emitting devices due to the advantages of heavy-metal-free characteristic and widely tunable spectrum covering most of the visible and near-infrared regions. However, the performance of InP quantum dot light-emitting diodes (QLEDs) lags far behind their Cd-containing counterparts, especially as the InP pixelated device is still in its infancy. In this study, multi-component functional QD inks with excellent stability and printability was developed for inkjet printing InP array QLEDs. High-quality QD films can be obtained, both on flat and bank-containing substrates, by precisely controlling the competition between capillary and Marangoni flows in the printed droplets, enabling high device performance. In addition, a periodic ZnO microlens arrays was prepared by nanoimprinting technology to enhance the light extraction efficiency of inkjet-printed InP QLEDs, leading to 127.6% improvement in external quantum efficiency (EQE) compared to the control device. The maximum luminance, EQE and current efficiency of the obtained device are 17,759 cd/m2, 8.1% and 11.1 cd/A, respectively. These results may facilitate the applications of high performance environment-friendly QLEDs by inkjet printing technology.