The Effect of Hydrogenated Amorphous Silicon on the Optical Properties of Solar Cells

Hydrogenated amorphous silicon (a-SiH) produced by plasma enhanced chemical vapor deposition (PECVD) is a very interesting material due to the possibility of controlling the energy band gap and the electrical properties by means of the alloy composition. In this work we focused on the intrinsic layer because it is responsible for light absorption and the subsequent charge carrier generation/separation and for photovoltaic stability under continuous illumination (StaeblerWronski) effect. We have prepared six sample of a-SiH (i-layer) A, B, C, D, E, F with varied H2 diluted (40, 50, 60, 70 sccm) and the deposition time is varied (30, 40 minutes) and the flow of SiH4 was fixed at 20 sccm. The pressure of chamber MPZ (modular process zones) before deposition process about 510-7 Torr. While during deposition process is 530 mTorr, the deposition temperature is 2700C and RF power is 1.8 watt. To evaluation the optical properties of the thin film we used multiple reflection method (NanoCalc-2000 measurement system). The absorption coefficient () of our samples are about 1.70710-3 (nm) -1, 1.55510-3 (nm) -1, 1.31210-3 (nm) -1, 1.29510-3 (nm) -1, 1.27010-3 (nm) -1and 1.25610-3 (nm) -1 respectively. The energy bandgap of the samples about 1.990 e. V, 1.916 e. V, 1.685 e. V, 1662 e. V, 1.594 e. V and 1.583 e. V respectively. Comparing our results with other researchers which it has the same deposition conditions but with difference deposition method (Hot Wire CVD systems) we can suggest that the efficiency of the layers (A up to F) about 6 % - 9 %.