Substrate dependent stability and interplay between optical and electrical properties in μc-Si:H single junction solar cells
In this work, we analyze the effect of rough ZnO front electrodes developed in-house favoring high current versus "smoother" substrates favoring good Voc and FF on the properties of microcrystalline silicon (μc-Si:H) cells. Complete μc-Si:H p-i-n solar cells with intrinsic layer thicknesses varying from 1 to 6μm were deposited using very high frequency plasma-enhanced chemical vapor deposition. The better scattering capabilities of rough substrates induce a significantly higher cell current in comparison to the smooth one for all the thicknesses. This allows a current output of more than 27 mA cm-2 for cells thicker than 4μm. As a result, there is no full compensation of poor light scattering by thickness increase up to 6μm in μc-Si:H solar cells. Concerning the electrical characteristics, good quality cells are obtained for all thicknesses on smooth substrates, whereas the thick cells on rough substrates exhibit poorer electrical characteristics. Cells grown on smooth substrates show excellent stability under light soaking and atmospheric storage for all the thicknesses. However, a high increase of the saturation current is evidenced after atmospheric storage for cells grown on rough substrates and thus a degradation of their electrical characteristics is observed. © 2010 Elsevier B.V. All rights reserved.