NOVELTY - A photovoltaic cell comprises a photon-absorbing layer (103) containing metal alloy nanoparticles copper, indium and/or gallium and is prepared by heating the nanoparticles sufficiently to permit reaction with material containing Group VA and/or VIA (preferably selenium and/or sulfur); an electrically conductive substrate for providing at least a portion of an electrical circuit in combination with the photon-absorbing layer; an emitting layer; and an anti-reflective coating.    USE - As a photovoltaic cell e.g. thin film solar cell for converting light energy into electricity.    ADVANTAGE - The photovoltaic cell has increased efficiency, reduced cost, and reduced weight. The photon-absorbing layer has reduced thickness thus increasing photovoltaic efficiency, and reducing material cost. The environmental layer reduces damages caused by weathering. The photovoltaic cell has increased surface area of the reactive metal alloy nanoparticles, as compared to surface area of metal substrate particles, primarily due to large number of atoms on the surface of the particles.    DETAILED DESCRIPTION - A photovoltaic cell comprises a photon-absorbing layer containing metal alloy nanoparticles having metal from Group IB, IIB or IIIA (preferably of formula Cu1In1-xGax, where x is 0-1), and is prepared by heating the nanoparticles sufficiently to permit reaction with material containing Group VA and/or VIA (preferably selenium and/or sulfur); an electrically conductive substrate supporting the photon-absorbing layer and providing at least a portion of an electrical circuit in combination with the photon-absorbing layer; an emitting layer containing material capable of absorbing electrons from the photon-absorbing layer; and an anti-reflective coating including material for permitting a significant amount of sunlight that strikes the cell to reach the photon-absorbing layer. The cell further comprises an environmental protection layer to reduce environmental degradation of the cell during use. The layer is less than 1 micron (preferably less than 500 nanometers). The nanoparticles are present in an amount of less than 50 nanometers. The nanoparticles are created using a vapor condensation process. INDEPENDENT CLAIMS are included for the following:    (1) preparing an electronic device, involving mixing on an electrically conductive substrate particles comprising at least one element selected from Groups VA and/or VIA with metal alloy nanoparticles made from a vapor condensation process; and heating the mixture to at least a reaction temperature that is sufficient to create a substantially fused layer of nanosized particles;    (2) a composition having photon-absorbing characteristics, comprising metal alloy nanoparticles made from a vapor condensation process, and is suitable for use in an electronic device; and    (3) a stratified layer of metal alloy nanoparticles of formula Cu1In1-xGax.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the photovoltaic cell (thin film solar cell).    Base material (101)    Substrate foil (102)    Photon-absorbing layer (103)    n-Type electron transporting emission layer (104)    Anti-reflective coating of zinc oxide (105)    Electrical contact (106)    Circuit. (107)