Si Solar Cell Kirsi Keronen 355825 Charlie Zhang

Si Solar Cell Kirsi Keronen, 355825 Charlie Zhang, 292821 Giovanni Marin, 337171 Muhammad Ali, 545442

How does it work? Front electrode (-) Antireflection coating N-type (P doped) P-type (B doped) Back electrode (+) Protective layer

Materials • Silicon (monocrystalline 3%, polycrystalline silicon) • Thin Films: Amorphous Si, Cadmium Telluride (Cd-Te), Copper Indium Gallium Selenide (Cu-In-Ga-Se) • Dopants: Boron (P-type), Phosphorous (N-type) • Titanium Dioxide, Silicon oxide and Aluminium oxide as anti-reflecting coating and passiavation • Support and protection: Glass 75%, steel and polymers • Contacts and Cables: Aluminium 10%, Silver, Copper, Zinc, etc.

State of art materials used • Black silicon SC • Thin film crystalline Si on glass

Comparison to Vesborg’s article • No mucho problemos!! • Uno problemo porfavore: silver • Inte so mycke problem, vi måste inte use that, vi kan use copper instäd

Erbium upconverter Improvement of 0, 19% S. Fischer, E. Favilla, M. Tonelli, and J. C. Goldschmidt, “Record efficient upconverter solar cell devices with optimized bifacial silicon solar cells and monocrystalline Ba. Y 2 F 8: 30% Er 3+ upconverter, ” Sol. Energy Mater. Sol. Cells, vol. 136, pp. 127– 134, May 2015

Black silicon solar cells with interdigitated back-contacts achieve 22, 1% efficiency Pic 1: Solar cells built with black silicon are much more lightabsorbent, and can capture incident photons from very low angles Result • B-Si property absorbing light with high acceptance angles -> the high efficiency can be maintained independently of the direction of the incoming light • Results show b-Si no longer limiting the cell efficiency -> further improvements possible by improving the cell structure • Efficiencies above 22% can be reached, even in thick interdigitated back-contacted cells, where carrier transport is very sensitive to front surface passivation Pic 2: A thin Al 2 O 3 layer is deposited on the nanostructured front surface Pic 3: a, SEM image of a b. Si surface. The 20 nm Al 2 O 3 is the brighter layer on top of the pillars. b, Reflectance spectra in the 300– 1, 000 nm wavelength range. The dashed line represents the reflectance of a bare b-Si sample and the black solid line shows the reflectance of b-Si with 20 nm of Al 2 O 3 Reference : Savin, H. Repo, P. Et al. Black silicon solar cells with interdigitated back-contacts achieve 22. 1% efficiency. Nature Nanotechnology, volume 10. Pages 624 -628. Published 18 May 2015. DOI: 10. 1038/nnano. 2015. 89

New efficient solar cell structures based on zinc oxide nanorods Why Zn. O nanorods? • Effective antireflection coating for cells • Deposit easily at low cost and in short time • Consider as good material for low cost solar cell technology Result • Zn. O nanorods grown on p- type silicon surface by hydrothermal method • Efficiency were different with Zn. O film thickness • Higher efficiency of 10. 9 % on 500 nm Zn. O film achieved Fig 1: Schematic diagram of the investigated solar cell structure Fig 2: Schematic diagram explaining the growth mechnism of Zn. O layer on nonorods in ALD growth chamber at 160 C and 1 mbar pressure Fig 3: High efficiency achieved on sample D of 10. 9% Reference : New efficient solar cell structures based on zinc oxide nanorods, R. Pietruszka, B. S. Witkowski, S. Gieraltowska, P. Caban, L. Wachnicki, E. Zielony, K. Gwozdz, P. Bieganski, E. Placzek-Popko, M. Godlewski, Solar energy Materials & Solar cells 143 (2015) 99 – 104

Graphenized Carbon Nanofiber Reference: X. Chen, B. Jia , B. Cai , J. Fang , Z. Chen , X. Zhang , Y. Zhao , and M. Gu, “Graphenized Carbon Nanofiber: A Novel Light. Trapping and Conductive Material to Achieve an Efficiency Breakthrough in Silicon Solar Cells” (2014). DOI: 10. 1002/adma. 201404123

Annealing at 250 °C. Ni. Si 2/Ni/Cu Ni. Si 2/Ni 71 Co 29/Cu Q. Huang, K. B. Reuter, Y. Zhu, and V. R. Deline, “A Study on the Long-Term Degradation of Crystalline Silicon Solar Cells Metallized with Cu Electroplating, ” ECS J. Solid State Sci. Technol. , vol. 5, no. 2, pp. Q 24–Q 34, Jan. 2016

Light-Induced degradation of Thin Film Silicon Solar Cells Thin Film Amorphous Silicon cell • Uses thin absorbing layer of few 100 nm resulting in • Lower material demand • Low production cost • But efficiency are low Problem • Light induced degradation (LID) result in lower efficiency • During LID weak silicon-hydrogen bond breaks and density of defects increases • LID depends on following parameters, quality of a. Si layer, thickness , temperature, light intensity Fig 1: Degradation of a-Si cells with different i-layer thickness Result • LID can be minimized by choosing right substrate, layer thickness • But decresing LID has disadvantage also like more raw material used, lower depostion rate and lower production output Fig 2: Efficiency of cells with different i-layer thickness during LID Reference: Light-Induced degradation of Thin Film Silicon Solar Cells, F U Hamelmann, J A Weicht and G Behrens, Journal of Physics, 682 (2016) 012002

Potential-induced degradation in photovoltaic modules based on n-type single crystalline Si solar cells • Result N-type • Surface polarization effect decreased the PV performance of a high efficiency n-type BC Si solar cell by applying high positive voltage to the Si cell • Degradation mechanism of PV modules by high voltage stress significantly depends on the structure and type of Si cell • PID easily occurred in n-type single crystalline Si PV modules, compared to p-type multicrystalline P-type • • PID can be basically avoided by using Na-free front cover substrates PID can be significantly suppressed by using a acrylic-film as a front cover substrate Fig 1: The spectra of external quantum efficiency for a standard n -type FJ Si PV module (a) before and (b) after PID test (− 1000 V at 85 °C for 2 h). Reference: Hara, K. Jonai, S. Masuda, A. Potential-induced degradation in photovoltaic modules based on n-type single crystalline Si solar cells. Solar Energy Materials and Solar cells. Volume 140, September 2015, Pages 361 -365.

Backsheets as protection Fig. 1. Illustrated incident light into the PV module and its reflection (schematic of cross-section of silicon photovoltaic module). Reference: N. Kim, S. Lee, X. G. Zhao, D. Kim, C. Oh, H. Kang, “Reflection and durability study of different types of backsheets and their impact on c-Si PV module performance” (2015). http: //dx. doi. org/10. 1016/j. solmat. 2015. 11. 038

Recycling of Si solar cells Charlie Zhang, Giovanni Marin, Muhammad Ali, Kirsi Keronen

Dong, A. ; Zhang, L. ; Damoah, L. ; “Beneficial and technological analysis for the recycling of solar grade silicon wastes”; JOM. 2011, 63, 23.

GHG emission of PV solar cells PV manufacturing >88% (37% Si) Operation <0. 1% Decommissioning 10% Energy requirement of PV PV manufacturing >88% (38% Si) Operation <0. 2% Decommissioning 11% Review of life cycle analyses and embodied energy requirements of single-crystalline and multi-crystalline silicon photovoltaic systems, J. h. Wong, M. Royapoor, C. W. Chan, Renewable and sustainable energy reviews 58 (2016) 608618

Indium • Limited production – Depended on the Zn production (by-product) – Not possible to adjust the production to the demand – Material lost if not extracted in the mine • No In is recycled at the moment • Used in small quantities in electronics • 580 t used in 2011, only 1% recovered • If In from ITO was recycled -> 380 t recovered up to 440 t if the deposition tech was 70% efficient