Laura Barrutia

On the use of I–V curves as a diagnosis tool for proper external quantum efficiency measurements of multijunction solar cells

External quantum efficiency measurement of multijunction solar cells is not an easy task. In this paper we propose to trace the I-V curve of the multijunction device under the same light bias conditions intended to be applied for the EQE measurement as an effective way to minimize artifacts and determine the optimum light and voltage bias conditions for the measurement. In this way, the analysis of the I-V curve will help to determine the proper voltage bias needed (if any), as well as to distinguish whether the external quantum efficiency measurement is being affected by shunt problems, early breakdown or luminescent coupling. This is of special relevance in order to determine the origin of the measurement artifact affecting the external quantum efficiency measurement of MJSCs.

On the use of Sb to improve the performance of GaInP subcells of multijunction solar cells

GaInP is a material commonly employed for the top subcells of different multijunction solar cells architectures. In this study, the performance of GaInP top cells has been improved by increasing the energy band gap with the use of Sb as a surfactant during the MOVPE growth of the structures. The optimization of the appropriate Sb molar flow was done by Reflectance Anisotropy Spectroscopy. Different characterization techniques have been employed to assess the effect of Sb on the morphology, microstructure and optoelectronic properties of the resulting GaInP grown with different Sb/P ratios. Finally, the performance of several GaInP subcells with different order parameters has been assessed.