Effect of bottom cell properties on micromorph tandem device performance

Paola Delli Veneri (1) , Lucia Vittoria Mercaldo (1) , Carlo Privato (1)

1 ENEA - Italian National agency for new technologies, Energy and sustainable economic development [Frascati]

Micromorph tandem solar cells represent an elegant way of overcoming the efficiency limits of single-junction solar cells and reducing the light-induced degradation of amorphous silicon films. Micromorph devices have been realized on Asahi U-type TCO-covered glass substrates by very high frequency plasma enhanced chemical vapour deposition (VHF-PECVD) at 100 MHz at low substrate temperature (150 °C). For the bottom cell different growth regimes have been explored by changing both chamber pressure and plasma power aiming at finding interesting regimes for industrial application. The effect of the structural composition of the microcrystalline absorber layer on the electrical parameters of the device has been investigated. The highest efficiency (11.1%) is reached at 67 Pa and power to pressure ratio of 0.3 W/Pa. On the other hand, using larger power to pressure ratio (0.5 W/Pa) high short circuit current density and constant efficiency in a wide silane concentration range are obtained. Homogeneity problems and low response at high wavelengths are found at large pressure (200 Pa). An evaluation of micromorph device stability has also been carried out.

Mots clés: Physical Sciences

Paola Delli Veneri, Lucia Vittoria Mercaldo, Carlo Privato. Effect of bottom cell properties on micromorph tandem device performance. Philosophical Magazine, 2009, 89 (28-30), pp.2645-2654. ⟨10.1080/14786430902785344⟩. ⟨hal-00519084⟩