a-Si:H/poly-Si tandem cells deposited by hot-wire CVD

Innovative multibandgap a-Si:H/poly-Si tandem solar cells have been developed, where the two absorbing layers have been deposited by hot-wire CVD. These n–i–p/n–i–p cells have been deposited on a flexible stainless steel substrate, where the microcrystalline doped layers are made by PECVD. No enhanced back reflector was applied. Although the bottom cell shows a shunting problem under low-light conditions, the best tandem cell has an efficiency of 8.1% under AM-1.5 illumination, a fill factor of 0.60, an open-circuit voltage of 1.18 V, and a short-circuit current density of 11.4 mA/cm2. The total thickness of the tandem structure is only 1.1 μm.