This title appears in the Scientific Report : 2015 

Modelling Performance of Two- And Four-terminal Thin-film Silicon Tandem Solar Cells under Varying Spectral Conditions
Reynolds, Steve (Corresponding author)
Smirnov, Vladimir
Photovoltaik; IEK-5
Energy procedia, 84 (2015) S. 251 - 260
Amsterdam [u.a.] Elsevier 2015
EMRS 2015 Spring meeting – Symposium C on Advanced Inorganic Materials and Structures for Photovoltaics, Lille (France), 2015-05-11 - 2015-05-15
Journal Article
Solar cells of the next generation
Please use the identifier: in citations.
Please use the identifier: in citations.
In an amorphous silicon/microcrystalline silicon or ‘micromorph’ tandem solar cell, variations in solar spectral quality alter the proportion of photo-generated current developed by each sub-cell. This imbalance may reduce long-term energy conversion efficiency, compared with operation under a constant AM1.5G spectrum. Using semi-empirical modelling, we contrast the usual series-connected two-terminal tandem cell, constrained by current-matching, with a four-terminal tandem cell, in which both sub-cells are electrically independent. The model reveals that reduction in extracted power due to current mismatch in two-terminal connection is compensated somewhat by an increase in fill-factor either side of the current-matched point. The efficiency-mismatch curve is compared with spectral distributions of annual insolation in terms of average photon energy. Provided the two-terminal cell is matched to the prevailing spectral distribution, long-term benefits in electrical energy output in four-terminal connection are predicted to be modest. However departures from the AM1.5G spectrum occur worldwide, and this plus the flexibility to match to seasonal degradation/annealing cycles suggests that four-terminal connection may offer greater benefit.