NOVELTY - Thin film solar cells and photodetectors are formed by forming macroscopic features having period spacing, width, and depth on first surface of a doped film, attaching an electrical contact to a second surface of the film, doping regions of surface of the macroscopic features and region of the surfaces between the features, attaching an electrical contact to portion of p-n junction with the doped film, and randomly etching 3-dimensional microscopic structures having dimensions less than wavelengths of light on the macroscopic features parallel to the film and on the macroscopic features.    USE - For forming thin film solar cells and photodetectors having increased light absorption and radiation tolerance.    ADVANTAGE - The photovoltaic device has enhanced optical absorption and enhanced tolerance to ionizing radiation for solar cells, space solar cell, and wavelength-selective photodetector applications, where enhanced infrared response is required as a result of insufficient film thickness for absorption or radiation-induced volume damage leading to low-lifetime material. The effective light trapping of the structures compensates for the removal of photovoltaic material and reduces the weight for space applications.    DETAILED DESCRIPTION - Formation of thin film solar cells and photodetectors having increased light absorption and radiation tolerance, involves forming macroscopic features having a chosen periodic spacing, width, and depth on a first surface of a doped film for solar cell or photodetector applications. Each feature has at least one surface perpendicular to the first surface of the film and one parallel surface, there also being formed surfaces between macroscopic features. An electrical contact is attached to at least a portion of a second surface of the film. The second surface is parallel to and spaced apart a chosen thickness from the first surface. The region of the surfaces of the macroscopic features and the region between the features are doped, thus forming a p-n junction with the doped film. An electrical contact is attached to at least a portion of the junction. The film produces a photovoltaic response to light having a chosen wavelength or wavelengths incident. The period of the macroscopic features, the width and the depth and the thickness between surfaces of the film are chosen so that minority carrier diffusion length for carriers produced by the photovoltaic response of the film is larger than the largest distance between a location interior to the film and the junction. 3-Dimensional microscopic structures having dimensions less than the wavelength(s) of light are randomly etched on the surfaces of the macroscopic features parallel to the film surface and on the surfaces between the macroscopic features so that light incident is scattered into high diffraction orders that propagate obliquely to the direction of incidence of light, thus trapping the incident light by total internal reflection and increasing light absorption by the film. The film has a thickness of 10-50 microns. An INDEPENDENT CLAIM is included for a photovoltaic device.    DESCRIPTION OF DRAWING(S) - The figure is a schematic representation of radiation-tolerant, thin film silicon photovoltaic device.