Thinner silicon-based tandem solar cell with high efficiency made by hot wire CVD

We developed thin film silicon tandem cells with hot-wire deposited amorphous (protocrystalline) and nanocrystalline i-layers, with a total thickness of only 1.43 µm. This is considerably thinner than the thickness of 2.5–3.0 µm normally needed, which is important to significantly reduce production costs for this type of cells. An initial efficiency of 8.84% was obtained. The top cell is ∼220 nm and the bottom cell only ∼1210 nm thick. No intermediate reflector layer is introduced. Compared to standard PECVD tandem cells, the Voc is remarkably high, consistent with the beneficial effect of thin i-layers on Voc and with the high Voc of 0.57 V obtained for single junction HWCVD nc-Si:H cells. After over 2000 hours of light soaking, a stabilized efficiency of 7.63% was obtained