Abstract
Currently, perovskite–silicon tandem solar cells are one of the most investigated concepts for overcoming the theoretical limit for the power conversion efficiency of silicon solar cells. For monolithic tandem solar cells, the available light must be distributed equally between the two subcells, which is known as current matching. For a planar device design, a global optimization of the layer thicknesses in the perovskite top cell allows current matching to be reached and reflective losses of the solar cell to be minimized at the same time. However, even after this optimization, the reflection and parasitic absorption losses add up to 7 mA / cm2. In this contribution, we use numerical simulations to study how well hexagonal sinusoidal nanotextures in the perovskite top-cell can reduce the reflective losses of the combined tandem device. We investigate three configurations. The current density utilization can be increased from 91% for the optimized planar reference to 98% for the best nanotextured device (period 500 nm and peak-to-valley height 500 nm), where 100% refers to the Tiedje–Yablonovitch limit. In a first attempt to experimentally realize such nanophotonically structured perovskite solar cells for monolithic tandems, we investigate the morphology of perovskite layers deposited onto sinusoidally structured substrates.
Highlights
Crystalline silicon (c-Si) solar cells have achieved enormous dominance in the photovoltaic market due to their high efficiencies, excellent material quality, and continual reduction in manufacturing costs
We decided to focus on hexagonal sinusoidal nanotextures,[22,23] which allow for the combination of a strong antireflective effect with good electrical performance, as we demonstrated for liquid-phase crystallized silicon thin-film solar cells.[24,25]
We investigate how sinusoidal nanotextures affect the optical performance of perovskite–silicon tandem solar cells
Summary
Crystalline silicon (c-Si) solar cells have achieved enormous dominance in the photovoltaic market due to their high efficiencies, excellent material quality, and continual reduction in manufacturing costs. The current record efficiency of 26.7%1 is already 89% of the theoretical limit value for the power conversion efficiency for single-junction solar cells.[2] Further improvement in this technology will become increasingly difficult. The incident sunlight first hits the top cell, which has a higher bandgap and harvests the high-energy photons at a higher voltage, whereas the low-energy photons are transferred to the bottom cell, which has a lower bandgap and corresponding lower voltage. Highenergy photons are able to contribute more voltage to the device instead of losing their excess energy by thermalization
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