NOVELTY - Composition for forming a photostable wavelength conversion material comprises a first organic chromophore; a first optically transparent crosslinkable polymer; and a first crosslinking reagent; or composition for producing a photostable wavelength conversion material for a solar energy conversion device comprises a first chromophore, a first optically transparent crosslinkable polymer, and a first crosslinking reagent, with the proviso that the chromophore is not within an oxide microparticle.    USE - The composition is useful for producing photostable wavelength conversion material for solar energy conversion device; for making wavelength conversion layer, encapsulation structure for solar energy conversion device, greenhouse panel, and greenhouse solar collection panel; and for improving performance of solar energy conversion device (all claimed).    ADVANTAGE - The film or layer is useful as an encapsulate for solar energy devices as it provides stable enhancement of the photoelectric conversion efficiency of these devices by converting photons from one wavelength into a different more desirable wavelength that can be more efficiently utilized by the solar energy device. Simultaneously, the film or layer, when used in an encapsulation structure, also provides stable long term environmental protection to the solar energy device from oxygen and water ingress as well as protection from harmful high energy ultraviolet photons.    DETAILED DESCRIPTION - Composition for forming a photostable wavelength conversion material comprises a first organic chromophore; a first optically transparent crosslinkable polymer; and a first crosslinking reagent; or composition for producing a photostable wavelength conversion material for a solar energy conversion device comprises a first chromophore, a first optically transparent crosslinkable polymer, and a first crosslinking reagent, with the proviso that the chromophore is not within an oxide microparticle; or composition for producing a photostable wavelength conversion material for a solar energy conversion device comprises a first chromophore, a first optically transparent crosslinkable polymer, and a first crosslinking reagent, where the at least one chromophore is a UV absorber; or composition for forming a photostable wavelength conversion material for a solar energy conversion device comprises a first organic chromophore; a first monomer, where upon polymerization the monomer yields an optically transparent crosslinkable polymer; and a first crosslinking reagent. INDEPENDENT CLAIMS are included for:    (1) a wavelength conversion layer formed by curing the composition;    (2) an encapsulation structure for a solar energy conversion device comprising the wavelength conversion layer; where the wavelength conversion layer is configured to encapsulate a solar energy conversion device and inhibit penetration of moisture and oxygen into the solar energy conversion device; and where the wavelength conversion layer is configured to encapsulate the solar energy conversion device such that light must pass through the wavelength conversion layer prior to reaching the solar energy conversion device; or an encapsulation structure for a solar energy conversion device comprising the wavelength conversion layer; and an environmental protective cover configured to inhibit penetration of moisture and oxygen into the wavelength conversion layer and the solar energy conversion device; and where the wavelength conversion layer and the environmental protective cover are configured to encapsulate the solar energy conversion device such that light must pass through the wavelength conversion layer and the environmental protective cover prior to reaching the solar energy conversion device;    (3) a method of improving performance of a solar energy conversion device, which involves encapsulating the device with the encapsulation structure;    (4) a greenhouse panel comprising at least one wavelength conversion layer;    (5) a greenhouse solar collection panel comprising at least one wavelength conversion layer and at least one solar energy conversion device; and    (6) a method of making a wavelength conversion layer which involves curing the composition.