Developmental experiments on large-area silicon solar cells

Abstract

A comprehensive design/material/technological study was conducted with the aim of obtaining high-efficiency back-surface-field- (BSF-) type bifacial solar cells with reproducible parameters on large-area n- and p-silicon wafers. Practical ways of attenuating the severe limitations imposed by different kinds of areal inhomogeneities on the electro-optical performance of large-area BSF single-crystal silicon solar cells are described and tested experimentally. Various procedures leading to a substantial increase of both the emitter and the base contributions to the generated photocurrent are implemented and discussed in detail. The p+-n-n+ and n+-p-p+ cells were processed as bifacial devices and tested under both front and backside AM1 illumination. The trial devices were fabricated on 2-in and 3-in. commercially available lower-grade silicon and the minimization of the cell cost was one of the sought-after objectives. The combination of simple design/technological approaches described in this work has ultimately led to the development of low-cost, high-efficiency (17%–18%) large-area silicon solar cells with good overall electro-optical performance as bifacial devices. The results of this work show clearly that simple, but adequately designed/processed cells fabricated on an industrial scale on large-area silicon wafers could possess parameters similar to those of sophisticated laboratory samples elaborated on small-area silicon. With the design/technological approaches outlined in this work, the use of even cheaper, i.e., lower-grade single-crystal silicon, could still yield 2- and 3-in. cells with fairly acceptable conversion efficiencies.