Investigation of parasitic absorption in back contact of CDTE solar cells

Joshua Smay, Ola Rashwan, James Then, Darien Perez

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Thin film solar cells (TFSC) differ from the conventional wafer solar cell panels in that they are a fraction of the thickness, hence they boast reduced material costs, lighter weight, and possible flexibility. To improve their light-trapping and absorption efficiency, manufacturers currently use nanometer scale texturing. When manufacturing nano textured thin film solar cells in the substrate configuration, the back reflector is also textured. It has been observed that a textured back reflector leads to parasitic light absorption in silicon solar cells. This occurrence reduces the back reflector effectiveness, and thus reduces absorption in the absorber layer and overall efficiency. However, there is little to no similar research done for thin film (CdTe/CdS ) solar cells devices. In this work, wave optical analyses of thin film CdTe/CdS solar cells with and without nano texturing on the metal back reflectors were simulated using ANSYS ANSOFT High Frequency Structural Simulator (HFSS). The optical analyses yielded percentage absorptions for unit cells with four absorber thicknesses range between 250-to 1000 nm, with and without a textured back reflector over six wavelengths range from 360nm to 860 nm, and with 3 different back contact metals (Au, Ag, and Al). It was noted that the textured back contacts show a substantial increase in the absorption in the active CdTe layer in the infrared range. Additionally, back reflector texturing increases the parasitic absorption in the metal back reflector layer as well, especially with ultrathin absorber layer. It was also found that additional parasitic absorption due to a textured back reflector has less of an impact on absorption as the active absorber thickness increases to 500 nm, 750 nm, or 1000 nm. Finally, silver (Ag) as back contact outperforms both aluminum (Al) and gold (Au). This finding might be crucial to solar cell manufacturers because it could possibly be an overlooked factor in achieving higher efficiencies for relatively thin cells.

Original languageEnglish (US)
Title of host publicationASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791851418
StatePublished - Jan 1 2018
EventASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum - Lake Buena Vista, United States
Duration: Jun 24 2018Jun 28 2018

Publication series

NameASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum

Other

OtherASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum
CountryUnited States
CityLake Buena Vista
Period6/24/186/28/18

Fingerprint

Texturing
Solar cells
Metals
Aluminum
Thin films
Silicon solar cells
Light absorption
Silver
Gold
Simulators
Infrared radiation
Wavelength
Substrates
Costs
Thin film solar cells

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment

Cite this

Smay, J., Rashwan, O., Then, J., & Perez, D. (2018). Investigation of parasitic absorption in back contact of CDTE solar cells. In ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum (ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum). American Society of Mechanical Engineers (ASME).
Smay, Joshua ; Rashwan, Ola ; Then, James ; Perez, Darien. / Investigation of parasitic absorption in back contact of CDTE solar cells. ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum. American Society of Mechanical Engineers (ASME), 2018. (ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum).
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Smay, J, Rashwan, O, Then, J & Perez, D 2018, Investigation of parasitic absorption in back contact of CDTE solar cells. in ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum. ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum, American Society of Mechanical Engineers (ASME), ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum, Lake Buena Vista, United States, 6/24/18.

Investigation of parasitic absorption in back contact of CDTE solar cells. / Smay, Joshua; Rashwan, Ola; Then, James; Perez, Darien.

ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum. American Society of Mechanical Engineers (ASME), 2018. (ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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AU - Rashwan, Ola

AU - Then, James

AU - Perez, Darien

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N2 - Thin film solar cells (TFSC) differ from the conventional wafer solar cell panels in that they are a fraction of the thickness, hence they boast reduced material costs, lighter weight, and possible flexibility. To improve their light-trapping and absorption efficiency, manufacturers currently use nanometer scale texturing. When manufacturing nano textured thin film solar cells in the substrate configuration, the back reflector is also textured. It has been observed that a textured back reflector leads to parasitic light absorption in silicon solar cells. This occurrence reduces the back reflector effectiveness, and thus reduces absorption in the absorber layer and overall efficiency. However, there is little to no similar research done for thin film (CdTe/CdS ) solar cells devices. In this work, wave optical analyses of thin film CdTe/CdS solar cells with and without nano texturing on the metal back reflectors were simulated using ANSYS ANSOFT High Frequency Structural Simulator (HFSS). The optical analyses yielded percentage absorptions for unit cells with four absorber thicknesses range between 250-to 1000 nm, with and without a textured back reflector over six wavelengths range from 360nm to 860 nm, and with 3 different back contact metals (Au, Ag, and Al). It was noted that the textured back contacts show a substantial increase in the absorption in the active CdTe layer in the infrared range. Additionally, back reflector texturing increases the parasitic absorption in the metal back reflector layer as well, especially with ultrathin absorber layer. It was also found that additional parasitic absorption due to a textured back reflector has less of an impact on absorption as the active absorber thickness increases to 500 nm, 750 nm, or 1000 nm. Finally, silver (Ag) as back contact outperforms both aluminum (Al) and gold (Au). This finding might be crucial to solar cell manufacturers because it could possibly be an overlooked factor in achieving higher efficiencies for relatively thin cells.

AB - Thin film solar cells (TFSC) differ from the conventional wafer solar cell panels in that they are a fraction of the thickness, hence they boast reduced material costs, lighter weight, and possible flexibility. To improve their light-trapping and absorption efficiency, manufacturers currently use nanometer scale texturing. When manufacturing nano textured thin film solar cells in the substrate configuration, the back reflector is also textured. It has been observed that a textured back reflector leads to parasitic light absorption in silicon solar cells. This occurrence reduces the back reflector effectiveness, and thus reduces absorption in the absorber layer and overall efficiency. However, there is little to no similar research done for thin film (CdTe/CdS ) solar cells devices. In this work, wave optical analyses of thin film CdTe/CdS solar cells with and without nano texturing on the metal back reflectors were simulated using ANSYS ANSOFT High Frequency Structural Simulator (HFSS). The optical analyses yielded percentage absorptions for unit cells with four absorber thicknesses range between 250-to 1000 nm, with and without a textured back reflector over six wavelengths range from 360nm to 860 nm, and with 3 different back contact metals (Au, Ag, and Al). It was noted that the textured back contacts show a substantial increase in the absorption in the active CdTe layer in the infrared range. Additionally, back reflector texturing increases the parasitic absorption in the metal back reflector layer as well, especially with ultrathin absorber layer. It was also found that additional parasitic absorption due to a textured back reflector has less of an impact on absorption as the active absorber thickness increases to 500 nm, 750 nm, or 1000 nm. Finally, silver (Ag) as back contact outperforms both aluminum (Al) and gold (Au). This finding might be crucial to solar cell manufacturers because it could possibly be an overlooked factor in achieving higher efficiencies for relatively thin cells.

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M3 - Conference contribution

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T3 - ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum

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Smay J, Rashwan O, Then J, Perez D. Investigation of parasitic absorption in back contact of CDTE solar cells. In ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum. American Society of Mechanical Engineers (ASME). 2018. (ASME 2018 12th International Conference on Energy Sustainability, ES 2018, collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum).