Characterizing the performance of terrestrial multi-junction solar cells under a broad range of sunlight concentration and operating temperatures is important for designing high concentration photovoltaic systems. Experimental data is available for these cells but a satisfactory cell model, calibrated over the full range of these operating conditions, was not yet presented. This study presents single-diode and two-diode equivalent circuit semi-empirical models for InGaP/InGaAs/Ge triple-junction cells, calibrated against available empirical data published by two cell manufacturers. The two-diode model offers a better fit to the experimental values compared to the single diode model. In particular, the two diodes model describes better the dependence of efficiency on concentration. However, some systematic deviations still exist in both models, mainly related to temperature dependence. Based on these results, two further modeling issues are identified as promising directions for further improvement of the models. (C) 2011 Elsevier B.V. All rights reserved.