Concentrators use reflection or refraction of light, or a combination of both, but concentration of light leads to a crucial heating of the cell, which involves degradation of its performance. However, solar cells especially conceived for concentration can support very intense illuminations as far as an active cooling is assured. In this work, a GaAs solar cell with AlxGa1-x As window layer, operating under low injection conditions, has been studied with temperature and solar concentration. The temperature corresponding to each concentration was calculated, and then used in the calculation of photovoltaic parameters. The study was carried out under free mode conditions (without heat sink) and then under forced conditions (with a cooling system) in order to demonstrate the importance of cooling in the concentrator solar cells. The effect of series resistance on solar cell characteristics has also been studied. The simulation was carried out using SCAPS-1D simulator. The results were compared with those obtained theoretically; a good agreement was found between the two models

Using a previous model, which was developed to describe the light-induced creation of the defect density in the a-Si:H gap states, we present in this work a computer simulation of the a-Si:H p-in solar cell behavior under continuous illumination. We have considered the simple case of a monochromatic light beam nonuniformly absorbed. As a consequence of this light-absorption profile, the increase of the dangling bond density is assumed to be inhomogeneous over the intrinsic layer (i-layer). We investigate the internal variable profiles during illumination to understand in more detail the changes resulting from the light-induced degradation effect. Changes in the cell external parameters including the open circuit voltage, V oc , the short circuit current density, J sc , the fill factor, FF, and the maximum power density, P max , are also presented. This shows, in addition, the free carrier mobility influence. The obtained results show that V oc seems to be the less affected parameter by the light-induced increase of the dangling bond density. Moreover, its degradation is very weak-sensitive to the free carrier mobility. Finally, the free hole mobility effect is found to be more important than that of electrons in the improvement of the solar cell performance.

Computer modelling and analysis of the photodegradation effect in a-Si:H p-in solar cell View the table of contents for this issue, or go to the journal homepage for more 2015 J. Semicond. 36 014002

Hydrogeneted amorphous silicon (a-Si:H) based solar cells are promising candidates for future developments in the photovoltaic industry. In fact, amorphous silicon technology offers significant advantages including low cost fabrication and possibility to deposition on flexible substrat as well as low temperature fabrication. Much progress has been made since the first single junction cell in amorphous silicon made in 1976 by Carlson and Wronski. However, the performance of the solar cells based on a-Si:H is limited by the high defect density and degradation induced by exposure to light, or Staebler-Wronski effect. To become competitive, the performance of the solar cells based on a-Si:H must be improved. In order to improve the performance of a-Si:H solar cells, much research is directed to optimization techniques. The improvement in performance is therefore based on the optimization of the different layers of the solar cell, in particular, the window layer and the absorber layer (intrinsic). The aim of this work is to give an overview on the different techniques and strategies that is used to improve the performance of solar cell. This work is therefore focus in three main areas: first, optimization of window layer, in particular, the p/i interface using wide band gap alloys such as a-SiC:H, second development of high quality absorber layer using band gap engineering, and alloys such as a-SiGe:H. last, optimizing n-type layer and i/n interface.