[ad_1]
Researchers at Chitkara University in India have designed and simulated a perovskite-CIGS tandem solar cell; the result was an efficiency of 29.7%.
I study “Perovskite-CIGS Monolithic Tandem Solar Cells with 29.7% Efficiency: A Numerical Study” examined a two-terminal monolithically stacked solar cell: the upper part in perovskite with an energy bandgap of 1.68 eV, the lower one based on CIGS, with a bandgap of 1.1 eV.
The design had a higher open circuit voltage, with the top cell acting as a current limiting cell.
The researchers conducted a numerical simulation to predict device performance and behaviorusing solar cell capacity software SCAPS-1D, a simulation tool for thin film solar cells developed by Ghent University in Belgium.
The team designed the bottom cell with a transparent, conductive indium zinc oxide (IZO) film, followed by a tin(IV) oxide (SnO2) buffer layer, a perovskite layer, and as the bore transport layer the methyl-substituted carbazole (Me-4PACz).
For the upper cell, the choice fell on the use of an indium tin oxide (ITO) substrate, a cadmium sulphide (Cds) layer and a CIGS absorber.
“In the upper cell, the perovskite layer acts as an absorber to capture high-energy photons. Similarly, the lower cell uses the CIGS layer to absorb low-energy photons”the scientists stated, highlighting how both cells are connected via an intermediate layer of ITO to provide the current match for the tandem configuration.
The team tested different thicknesses of the CIGS absorber layerfrom 0.5 micrometres (μm) up to 5 μm: in this way they were able to establish 2.3 μm the perfect thicknesswhere a greater absorption of photons corresponded to an increase in current density.
Moreover, it was discovered that there is current density saturation for thickness beyond 2.3 μm.
With an optimized absorber thickness of 2.3 μm, the bottom cell shown in the simulation can achieve a power conversion efficiency of 16.26%, an open circuit voltage of 0.64V, a short circuit current of 35.98 mA/cm2 and a fill factor of 70.51%.
The tandem device upper/lower cell thickness of 347 nm/2.0 μm showed an efficiency of 29.72%, an open circuit voltage of 1.92 V, a short circuit current of 20.04 mA/ cm2 and a fill factor of 77%.
“The voltage drop across the tandem solar cell is the sum of the voltage drop across both subcells individually”said the team, adding that the upper cell delivers less current than the lower cell in the standalone configuration and acts as a current limiting cell.
“The major limitation of the filtered spectrum approach adopted is that it ignores interfacial reflection losses and interference effects”reads a note from the study ‘The transfer matrix method (TMM) can therefore be used in the future to calculate a more accurate filtered spectrum.’
.
[ad_2]
Source link
