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Comparison of distributed vs. lumped series resistance modeling of thin‐film solar cells and modules: Influence on the geometry‐dependent efficiency
Author(s) -
Seeland Marco,
Hoppe Harald
Publication year - 2015
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201431886
Subject(s) - materials science , sheet resistance , equivalent series resistance , solar cell , pedot:pss , optoelectronics , organic solar cell , electrode , polyethylene terephthalate , polyethylene naphthalate , active layer , short circuit , electrical conductor , indium tin oxide , composite material , polymer solar cell , energy conversion efficiency , layer (electronics) , voltage , thin film transistor , polymer , electrical engineering , chemistry , engineering
Limited lateral conductivities of the photo‐active materials used in thin‐film solar cells necessitate the use of semitransparent electrodes for current collection and lateral current transport. Due to the tradeoff between electrical conductivity and optical transmission, which should not underrun 80%, typical values for the sheet resistances of semitransparent electrodes deposited on glass amount to 10–20 Ω/sq. The power loss due to Joule heating and the accompanying voltage drop caused by this sheet resistance increases with cell length in current transport direction and thus, defines an upper limit for practical solar cell lengths. In the several approaches existing for calculation of the power loss, the semitransparent electrode layer is either modeled as one lumped resistance in series to the solar cell or as distributed resistance across the whole length of the solar cell in current transport direction. We present a quantitative comparison between these two conceptions to investigate the direct influence on the optimal solar cell geometry and to discuss the capabilities as well as limitations of each model. The computational study presented here is based on the material system PCDTBT:PC 70 BM (poly[N‐9′‐hepta‐decanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] blended with phenyl‐C 70 ‐butyric‐acid‐methyl‐ester) for the photo‐active layer and commonly used semitransparent conductive electrodes: ITO (indium doped tin‐oxide) deposited on glass as well as on PET (polyethylene terephthalate) foil and highly doped PEDOT:PSS (poly(ethylene‐dioxy‐thiophene):poly(styrene‐sulfonic acid)) named PH1000 on PET foil.