▎ 摘　　要

NOVELTY - Composite material comprises graphene quantum dots and COOM groups bound to the surface of the graphene quantum dots, where M is alkali metal element. USE - The composite material is useful in quantum dot light-emitting diode (claimed). ADVANTAGE - The material: modifies graphene quantum dots with alkali metal surfaces and reduces the work function of graphene quantum dots. DETAILED DESCRIPTION - INDEPENDENT CLAIM are also included for: (1) preparing composite material comprising providing graphene quantum dot solution, binding the surface of graphene quantum dots with carboxylic acid groups, providing alkali metal carbonate aqueous solution, mixing the graphene quantum dot solution with alkali metal carbonate aqueous solution and reacting to obtain final product; (2) quantum dot light-emitting diode comprising anode, cathode, arranging quantum dot light emitting layer between anode and cathode, arranging electron transport layer between cathode and quantum dot light-emitting layer, where electron transport layer material is composite material; and (3) preparing quantum dot light-emitting diodes comprising providing anode forming quantum dot light-emitting layer on the anode, forming electron transport layer on the quantum dot light-emitting layer, where the electron transport layer material is composite material forming cathode on the electron transport layer to obtain quantum dot light-emitting diode.