a materials structure is presented which is based on the insertion of preformed nanocrystals of arbitrary shape on or into a non - crystalline , non - hydrocarbon barrier layer . embodiments of the structure include a variety of barrier layers and contacts , which can be layered . when the structure is used as a detector or a solar cell , transport of charged carriers created in the nanocrystals during the absorption process occurs through quantum mechanical tunneling , thermionic emission or diffusion to electronic contacts . one embodiment of such a structure is a photovoltaic device , where a built - in bias is established using different contact materials and barrier layers . the structure can also be used as a modulator or emitter . the invention may consist of many structures stacked and sharing adjacent contact regions , where individual layers are tuned to absorb , emit or modulate light at a specific frequency or groups of frequencies .