Tandem solar cells deposited using hot-wire chemical vapor deposition

The hot-wire chemical vapor deposition technique was used for the deposition of amorphous and microcrystalline silicon. The best microcrystalline silicon solar cells were deposited at the edge of the transition from the microcrystalline to the amorphous regime. Under conditions that are close to this edge, the crystalline ratio decreased with accumulated film thickness, due to changes in the filament properties during deposition. Microcrystalline silicon made at slightly higher hydrogen dilution was homogeneously structured. Multibandgap a-Si:H/μc-Si:H solar cells were made, and high open-circuit voltages were obtained for both n–i–p/n–i–p and p–i–n/p–i–n structures. The tunnel-recombination junction of n–i–p/n–i–p cells requires careful optimization in order to prevent current leakage under low light intensity conditions, such as during spectral response measurements.