Presentation Details
Considerations for a CdTe/CdSeTe two-terminal tandem solar cell

Aparajita Dixit, Scott Lambright, Alexander Bordovalos, Balaji Ramanujam, Isuru Lakmal, Adam Phillips, Nikolas Podraza, Michael Heben , Randy Ellingson.

The University of Toledo, Toledo, OH, USA

Abstract


We developed a monolithic two-terminal (2T) CdTe/CdSeTe tandem solar cell architecture on Tec12D glass substrate using a simulation-based transfer-matrix method (TMM) parameterized by measured wavelength-dependent optical constants n(λ), k(λ), and layer thicknesses. Here, we evaluate an all-inorganic CdTe/CdSeTe 2T tandem solar cell, with the intention of eventually replacing the CdTe top cell with a wider band gap cadmium chalcogenide ternary like CdxMn1-xTe or CdxZn1-xTe. However, modeling shows a thin top CdTe absorber (Eg =1.45eV) - a thicker CdSeTe bottom absorber with tunable band gap and an intermediate layer or recombination/tunnel junction of ITO combines in series, and an Au as back reflector. Layer-resolved absorptance, position-resolved field intensity, and depth-dependent generation rate profiles show that thickness-asymmetric absorption edges drive effective spectral splitting, optical dissipation peaks near the CdTe/ITO interface and decays through CdSeTe, and the photocurrent can be brought close to current matching. ERE helps optimize the thermal budget for the absorbers and tunnelling layer, which reduces the chlorine concentration and, in turn, impacts the open-circuit voltage. The incorporation of Group V dopants still needs to be explored to achieve better passivation.

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