Thin film tandem solar cell : Thin film tandem solar cell

Requires: SSuprem 4/BLAZE/TFT/Luminous
Minimum Versions: Atlas 5.22.1.R

This example demonstrates both IV and EQE simulations of a tandem a-Si:H/uc-Si:H solar cell based on the following reference:

M.Zeman and J.Krc, "Optical and electrical modeling of thin-film silicon solar cells" J. mater. res., Vol 23, No. 4, April 2008

A microphah solar cell with the following structure was used in the simulation: ZnO:Al(500nm)/p-a-Si:H(10nm)/i-a-Si:H(200nm)/n-a-Si:H (15nm)/p-uc-Si:H(10nm)/i-uc-Si:H(2.2um)/p-uc-Si:H(15nm)/ZnO(100nm)/Ag.

The Tauc-Lorentz dielectric function with Urbach Tail model for complex index of refraction was used for a-Si:H material. The model parameters were calibrated to fit the EQE of the top cell. For the bottom cell silicon index of refraction was used except that the imaginary part of the index of refraction was shifted in energy to take into account the band gap difference between silicon and uc-Si:H material. No specific calibration was performed here.

In order to model the interlayer between the two solar cells an original and simple method was used. Note that a more physical approach can be used as well using the NLBBT model as illustrated in The method used here consists of adding an electrode which exactly overlay the interlayer and attaching a lumped resistance to it using the contact name=com resist=1e16 statement. In doing this, we force the current to flow from Anode to Cathode and prevent any current to flow in the added electrode. Physically it can be justified by the fact the interlayer is acting like a resistor letting current flows without significant limitation. The value of the resistance can be used to adjust the amount of current allowing to flow through the added electrode thus controling the interlayer resistance.

In hydrogenated amorphous silicon (a-Si:H), the effect of dangling-bond states on recombination can be significant. The dangling-bond states are amphoteric and located around the middle of the bandgap. In this example the amphoteric parameter on the defect statement was used to specify amphoteric defects.

While in mechanically stacked Multi Junction cells, the subcells usually have separate contacts, monolithic Multi Junction cells are epitaxilly grown on one substrate, and the subcells are interconnected in series by tunnel diodes, leading to a standard two terminal contact. Thus the subcells are not accessible separately and the spectral response of a certain subcell has to be measured by using the effect of current limitation. In this example we shown how to accurately extract the spectral response in order to compare simulation and measurement in a reliable way.

To load and run this example, select the Load example button in DeckBuild. This will copy the input file and any support files to your current working directory. Select the run button to execute the example.