Energy-harvesting photovoltaic transparent tandem devices using hydrogenated amorphous and microcrystalline silicon absorber layers for window applications

Transparent photovoltaic (TPV) tandem devices were prepared via plasma-enhanced chemical vapor deposition, using hydrogenated amorphous (a-Si:H) and microcrystalline (mc-Si:H) absorber layers that were sandwiched by transparent conducting oxide (TCO) electrodes. The high-performance TPV tandem devices were designed by controlling the film thickness of the mc-Si:H absorbers. For the TPV tandem devices with 300-nm-thick a-Si:H top cells, increasing the absorber thickness (t(bottom)) of mc-Si:H bottom cells from 1.0 to 2.1 mu m induced an increase in power conversion efficiencies (PCEs) from 6.5% to 8.3% with a minor decrease in the average light transmittance from 16.6% to 14.6% at the 500-800 nm wavelengths. The TPV tandem devices exhibited JSC gains from 4.3 mA cm(-2) (t(bottom) = 1.0 mu m) to 0.5 mA cm(-2) (t(bottom) = 2.3 mu m) under bifacial illumination (front: 100 mW cm(-2) and rear: 30 mW cm(-2)). This further resulted in additional PCE gains from 2.8% (t(bottom) = 1.0 mu m) to 0.4% (t(bottom) = 2.3 mu m), in comparison to the corresponding samples under front illumination only. The TPV tandem devices demonstrated excellent PV performance even at low-light illumination intensities (-21 mW cm(-2)) in comparison to those at standard illumination light intensity (100 mW cm(-2)), while maintaining PCE values as high as 80%.

Automated summary

Transparent photovoltaic tandem devices with controlled absorber thickness exhibited high power conversion efficiencies and improved performance under bifacial illumination. These devices maintained excellent PV performance even at low-light intensities.