▎ 摘　　要

NOVELTY - Composite film comprises graphene quantum dot film and alkylsilane. The surface of graphene quantum dot film has oxygen-containing group, and alkylsilane is combined with oxygen-containing group. USE - Composite film for preparing quantum dot light-emitting diode (claimed). ADVANTAGE - The composite film achieves purpose of adjusting the work function of graphene quantum dot film by connecting alkylsilane on surface of graphene quantum dot film, and expands application range of the graphene quantum dot film as a charge transport material. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a method for preparing a composite film, which involves providing a graphene quantum dot solution; providing a substrate, depositing graphene quantum dot solution on substrate, and forming a graphene quantum dot film on the substrate; and providing an alkylsilane solution, and immersing substrate on which graphene quantum dot film is formed in alkylsilane solution to react the alkylsilane with oxygen-containing groups on surface of graphene quantum dot film to obtain the composite film; (2) a quantum dot light-emitting diode, which comprises an anode, a cathode, and a quantum dot light-emitting layer arranged between anode and cathode, and further comprises a hole transport layer arranged between anode and quantum dot light-emitting layer, where hole transport layer is composite film, or an electron transport layer is arranged between cathode and quantum dot light-emitting layer, and electron transport layer is composite film, or a hole transport layer is provided between anode and quantum dot light-emitting layer, an electron transport layer is provided between cathode and quantum dot light-emitting layer, and hole transport layer and electron transport layer is composite film; and (3) a method for preparing a quantum dot light-emitting diode, which involves providing an anode, forming a hole transport layer on the anode; forming a quantum dot light-emitting layer on hole transport layer, and forming a cathode on quantum dot light-emitting layer to obtain quantum dot light-emitting diode; or providing anode, forming quantum dot light-emitting layer on anode, forming electron transport layer on quantum dot light-emitting layer, where electron transport layer is the composite film, and forming electron transport layer on top of cathode to obtain quantum dot light-emitting diode; or providing anode, forming hole transport layer on the anode, forming a quantum dot light emitting layer on hole transport layer, forming electron transport layer on quantum dot light emitting layer, forming a hole transport layer on electron transport layer, forming cathode, where at least one of hole transport layer and electron transport layer is the composite thin film.