Improvement in the Transport of Charge Carriers in Tunnel Junctions of Silicon-Based Thin Film Tandem Solar Cells

We report new results on a tunneling junction for tandem solar cells using a nano-structured amorphous silicon p+layer (na-Si p+) as the recombination layer inserted between the n layer and the p layer. Devices were characterized by their dark current-voltage behavior (I-V), activation energy (Ea) and quantum efficiency (QE). The result shows that the tunnel junction with a na-Si p+insertion layer has higher recombination rates with higher density of defect states of about 2.7×1019cm-3, lower resistance with activation energy of 22meV. The tunnel junction with a na-Si p+insertion layer could be easily integrated into the tandem solar cell deposition process.

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Good Quality N (a-Si)-P+(Na-Si)-P (μC-Si) Tunnel Junction for Tandem Solar Cells

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.181-182.336 ◽

2011 ◽

Vol 181-182 ◽

pp. 336-339

Author(s):

Lan Li Chen ◽

Ming Ji Shi ◽

Jia Hui Yu

Keyword(s):

Activation Energy ◽

Solar Cells ◽

Tunnel Junction ◽

Deposition Process ◽

Defect States ◽

Recombination Rates ◽

Tandem Solar Cells ◽

Current Voltage ◽

Density Of Defect States ◽

Recombination Junction

A new tunnel-recombination junction model was proposed to increase the recombination of n/p junctions in tandem solar cells. According to the model, we fabricated a new tunnel junction with a nanostructured amorphous silicon p+(na-Si p+) layer inserted between the n layer and the p layer. To compare with the conventional method, we fabricated another tunnel junction with an amorphous p+(a-Si p+) insertion layer. Both devices were characterized by their dark current-voltage behavior (I-V), activation energy (Ea) and quantum efficiency (QE). The result shows that the tunnel junction with a na-Si p+insertion layer has higher recombination rates with higher density of defect states of about 2.7×1019cm-3, lower resistance with activation energy of 22meV. The tunnel junction with a na-Si p+insertion layer could be easily integrated into the tandem solar cell deposition process.

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Defect Spectroscopy on Damp-Heat Treated ZnO/CdS/Cu(In,Ga)(S,Se)2/Mo Heterojunction Solar Cells

Zeitschrift für Naturforschung A ◽

10.1515/zna-2003-1205 ◽

2003 ◽

Vol 58 (12) ◽

pp. 691-702 ◽

Cited By ~ 4

Author(s):

C. Deibel ◽

V. Dyakonov ◽

J. Parisi

Keyword(s):

Heat Treatment ◽

Activation Energy ◽

Solar Cells ◽

Deep Level ◽

Heat Exposure ◽

Continuous Distribution ◽

Open Circuit ◽

Defect States ◽

Band Bending ◽

Test Cells

The changes of defect characteristics induced by accelerated lifetime tests on solar cells of the heterostructure ZnO/CdS/Cu(In,Ga)(S,Se)2/Mo are investigated. Encapsulated modules were shown to be stable against water vapor and oxygen under outdoor conditions, whereas the fill factor and open-circuit voltage of non-encapsulated test cells are reduced after prolonged damp heat treatment in the laboratory, leading to a reduced energy conversion efficiency. We subjected non-encapsulated test cells to extended damp heat exposure at 85 ◦C ambient temperature and 85% relative humidity for various time periods (6 h, 24 h, 144 h, 294 h, and 438 h). In order to understand the origin of the pronounced changes of the cells, we applied temperature-dependent current-voltage and capacitance voltage measurements, admittance spectroscopy, and deep-level transient spectroscopy. We observed the presence of electronic defect states which show an increasing activation energy due to damp heat exposure. The corresponding attempt-to-escape frequency and activation energy of these defect states obey the Meyer-Neldel relation. We conclude that the response originates from an energetically continuous distribution of defect states in the vicinity of the CdS/chalcopyrite interface. The increase in activation energy indicates a reduced band bending at the Cu(In,Ga)(S,Se)2 surface.We also observed changes in the bulk defect spectra due to the damp-heat treatment. - PACS: 73.20.hb, 73.61.Le

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