Theoretical and experimental behavior of monolithically integrated crystalline silicon solar cells

A concept for the fabrication of monolithically integrated silicon solar cells is presented. The concept is based on standard Si wafer technology and does not use thin-film approaches. A key feature is isolation trenches dividing the wafer into several unit solar cells. Due to the imperfect isolation between unit cells defined on the same conductive wafer, some device aspects deviating from an ordinary series connection of solar cells arise. For the theoretical description, a model proposed by Valco [G. J. Valco, V. J. Kapoor, J. C. Evans, Jr., and A. T. Chin, in Proceedings of the 15th IEEE Photovoltaic Specialists Conference, Orlando, FL (1981), p. 187] has been generalized by using a two-diode concept for the unit cells and by weakening the assumption of identical unit cells. The model was used to simulate the cell performance in dependence on light intensity, isolation resistance, cell area, and number of unit cells. As a result, general design rules for these truly monolithically integrated solar cells are given. The theoretical predictions could be partially confirmed by experimental prototypes. The best cell with a total area of 21 cm(2) and six unit cells exhibits an open-circuit voltage of 3.43 V and a conversion efficiency of 10.9% under 100 mW/cm(2) AM1.5G illumination and standard reporting conditions. (C) 2000 American Institute of Physics. [S0021-8979(00)06903-6].