NOVELTY - Optoelectronic device (10) (I), comprises: (a) an anode (13); (b) a hole injection/transport layer (15) disposed on the anode, where the hole injection/transport layer includes a gradient distribution of transparent conductive nanoparticles so as to provide refractive index matching between the anode and the hole injection/transport layer; (c) an active layer (17) disposed on the hole injection/transport layer; and (d) a cathode (19) disposed on the active layer.    USE - The optoelectronic device is useful: for fabricating substrate (claimed); and as LED or photovoltaic device.    ADVANTAGE - The optoelectronic device: exhibits enhanced light extraction efficiency and increased device lifetime; provides improved refractive index matching between the substrate and the hole injection/transport layer; and enables faster separation and transport of electron hole pairs in the emission layer, thus providing a three-dimensional nanoscale transparent conducting oxide network.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) an optoelectronic device (II), comprising: (a1) a transparent conductive oxide layer deposited on a substrate; (b1) the hole injection/transport layer disposed on the transparent conductive oxide layer, where the hole injection/transport layer includes a gradient distribution of transparent conductive nanoparticles disposed in a hole-transport material so as to provide refractive index matching between the transparent conductive oxide layer and the hole injection/transport layer; and (c) and (d) as above per se; and    (2) fabricating the optoelectronic device, comprising: (A) producing a mixture of transparent conductive nanoparticles and the hole-transport material; (B) applying a layer of the mixture onto the anode to form the hole injection/transport layer, where the transparent conductive nanoparticles in the hole injection/transport layer forms the gradient distribution; (C) depositing the active layer onto the hole injection/transport layer; and (D) depositing the cathode on the active layer.    DESCRIPTION OF DRAWING(S) - The figure shows a cross sectional view of the optoelectronic device.    Optoelectronic device (10)    Anode (13)    Hole injection/transport layer (15)    Active layer (17)    Cathode (19)