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| Home > Publications database > Efficient multijunction thin film silicon solar cells with open-circuit voltages up to 2.8 V for the application in photoelectrochemical energy storage devices |
| Home > Publications database > Efficient multijunction thin film silicon solar cells with open-circuit voltages up to 2.8 V for the application in photoelectrochemical energy storage devices |
| Conference Presentation (Other) | FZJ-2015-03194 |
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2015
Abstract: We report on the development of multijunction solar cells for the integration in photoelectrochemical devices for hydrogen production. Hydrogen, as a storable chemical fuel, can be generated through photoelectrolysis of water, a chemical reaction which requires potentials, i.e. photovoltages over 1.8V to run autonomously. The exact voltage needed varies with the used catalysts. The photocurrent at the respective required voltage determines the solar-to-hydrogen device efficiency. It is therefore important to develop solar cells which can cover up a wide voltage (VOC and VMPP) range in combination with high photocurrents. This high photovoltage/high photocurrent tradeoff can be solved by multijunction solar cells made of amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon.We developed a-Si:H/a Si:H tandem, a Si:H/µc Si:H/µc Si:H and a Si:H/a Si:H/µc Si:H triple, and a Si:H/a Si:H/µc Si:H/µc Si:H quadruple junction solar cells. The solar cells were optimized in terms of photovoltage and photocurrent by varying the process parameters and thickness of the intrinsic absorber layers and by integrating microcrystalline silicon oxide as intermediate reflecting layers to adjust the photocurrents of the individual subcells. It was found that the electronic properties of the individual series-connected subcells can be adjusted to systematically tune the VOC between 1.9 V and 2.8 V and we achieved PV efficiencies over 11.5% for tandem and over 13.5% for triple and quadruple cells.
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