Method of making an enhanced optical absorption and radiation tolerance in thin-film solar cells and photodetectors

Abstract

Subwavelength random and periodic microscopic structures are used to enhance light absorption and tolerance for ionizing radiation damage of thin film and photodetectors. Diffractive front surface microscopic structures scatter light into oblique propagating higher diffraction orders that are effectively trapped within the volume of the photovoltaic material. For subwavelength periodic microscopic structures etched through the majority of the material, enhanced absorption is due to waveguide effect perpendicular to the surface thereof. Enhanced radiation tolerance of the structures of the present invention is due to closely spaced, vertical sidewall junctions that capture a majority of deeply generated electron-hole pairs before they are lost to recombination. The separation of these vertical sidewall junctions is much smaller than the minority carrier diffusion lengths even after radiation-induced degradation. The effective light trapping of the structures of the invention compensates for the significant removal of photovoltaic material and substantially reduces the weight thereof for space applications.