NOVELTY - Solid state device (D1) comprises, a structure (101) comprising: a first region of first rare earth composition; and a second region of second composition comprising of group IV elements in contact with the first region, where the first region is in a first state of strain and the second region is in a second state of strain such that the second region is operable as a direct band gap semiconductor.    USE - The solid state device useful for converting incident radiation into electrical energy (claimed), where the device includes solar cells or photovoltaic devices.    ADVANTAGE - The device exhibits increased conversion efficiency by harvesting a larger portion of the solar spectrum than conventional technology.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a solid state device (D2) for converting incident radiation into electrical energy comprising a first region comprising rare earth ions of first composition and quantum dots of second composition comprising carbon-silicon-germanium-tin of formula (CvSixGeySnz) (I), where at least one of v, x, y, z is greater than zero such that the quantum dots are operable to convert a portion of the incident radiation from a first energy to a second energy and transfer the second energy to the rare earth ions; and    (2) a solid state device (D3) for converting incident radiation into electrical energy comprising: a photovoltaic cell; a first region comprising rare earth ions of composition (rare earth oxide)1 adjacent the photovoltaic cell; and a second region comprising a group IV semiconductor in contact with the first region, where the group IV semiconductor is operable to convert a portion of the incident radiation from a first energy to a second energy and place a portion of the rare earth ions in an excited state by transfer of the second energy to the rare earth ions such that the excited rare earth ions are operable to photoluminesce at a predetermined wavelength.    DESCRIPTION OF DRAWING(S) - The figure shows schematic illustrations of solid state device.    Structure (101)    Semiconductor layers (105, 115)    Rare earth layer (110)