MINORITY-CARRIER COLLECTION ENHANCEMENT MODEL FOR THE DEEPLY GROOVED SOLAR-CELL

Although many, solar cell designs for low-concentration linear focus a pplications have utilized the 'prismatic cover' for reducing gridline shading, the deeply grooved solar cell represents an effort to integra te the prismatic cover into the basic device design for performance en hancement. The design is based on deep (140-mu m) grooves in [100] ori entation silicon, with an active-area silicon 'ridge' between gridline s. The silicon ridge should improve minority carrier collection effici ency, as compared to planar designs, due to the two-dimensional nature of current collection, and the placement of light on the ridge by the focus of the prismatic cover. This article describes the enhancement mechanism by using a model based on the superposition of two specific solutions of the transport equation. The enhancement model is in suppo rt of the approximation that for one-dimensional numerical modeling, t he 'effective' diffusion length is the sum of the bulk silicon diffusi on length and the height of the ridge. Data collected from prototype s olar cells provide some experimental support for the model, but diffic ulty in fabrication using typical semiconductor processing has limited full realization of the structure.