A device comprises an anode; a cathode; a layer therebetween comprising quantum dots; and a first layer comprising a material capable of transporting and injecting electrons in, or forming, contact with the cathode, the material comprising nanoparticles of an inorganic semiconductor material. In one embodiment of the device, quantum dots comprise a core comprising a first semiconductor material that confines holes better than electrons in the core and an outer shell comprising a second semiconductor material that is permeable to electrons. In another embodiment of the device, the nanoparticles comprise n-doped inorganic semiconductor material, and a second layer comprising a material capable of transporting electrons is disposed between the layer including quantum dots and the first layer, wherein the second layer has a lower electron conductivity than the first. In a further embodiment of the device, the first layer is UV treated. A method and other embodiments are also disclosed.