Experimentally observed deviations from the superposition principle in crystalline silicon solar cells at low illuminations

Abstract

The characteristics of several silicon single crystal cells were measured in the dark and at roughly AM1.5 illumination. The circuit model parameters were extracted from the characteristics, and significant differences were observed between the dark and illuminated parameter values. These differences caused significant shortfalls in the maximum power output of the cells when compared with the predictions made using the superposition principle. Three inch cells designed for AM1.5 operation showed a shortfall of 6% at 50°C, while the concentrator cell showed a shortfall of 1%. The shortfalls increased markedly with increasing cell temperature. The possibility of artifacts being introduced is investigated and discounted. Attempts to attribute the observations to distributed series resistance effects were unsuccessful. © 1987.