A high-performance quantum dot light-emitting diode (QLED) with heavy metal free (HMF) quantum dots (QDs) is urgently needed for its application in next-generation eco-friendly displays. However, the preparation of high-performance HMF QD materials and the corresponding electroluminescent devices remain challenges at present, especially for blue-emitting devices. In this work, by adjusting the Te/Se ratio of the ZnSeTe core, ZnSeTe/ZnSe/ZnS blue QDs with adjustable energy levels and emission peaks are demonstrated. These QDs are utilized to fabricate top-emitting QLEDs, yielding a peak current efficiency (CE) of 11.8 cd A–1. To make it one step further to meet the requirement of the wide color gamut in displays, the devices’ color coordinates and current efficiency are simultaneously optimized by adjusting their microcavity structure and electrical properties. Finally, the chroma efficiency (current efficiency/CIEy) of the blue devices is optimized to 72, which is 2.2 times that of the control device.