Back-contacted BaSi2 solar cells: an optical study

We present the optical investigation of a novel back-contacted architecture for solar cells based on a thin barium (di)silicide (BaSi2) absorber. First, through the analysis of absorption limits of different semiconducting materials, we show the potential of BaSi2 for photovoltaic applications. Then, the proposed back contacted BaSi2 solar cell design is investigated and optimized. An implied photocurrent density of 40.3 mA/cm in a 1-μm thick absorber was achieved, paving the way for novel BaSi2-based thin-film solar cells. © 2017 Optical Society of America OCIS codes: (040.5350) Photovoltaic; (050.1950) Diffraction gratings; (230.1480) Bragg reflectors; (350.6050) Solar energy. References and links 1. ©Fraunhofer ISE: Photovoltaics Report, updated: 17 November 2016. 2. M. A. Green, K. Emery, Y. Hishikawa, W. Warta, and E. D. Dunlop, “Solar cell efficiency tables (version 48),” Prog. Photovolt. Res. Appl. 24(7), 905–913 (2016). 3. K. Morita, Y. Inomata, and T. Suemasu, “Optical and electrical properties of semiconducting BaSi2 thin films on Si substrates grown by molecular beam epitaxy,” Thin Solid Films 508(1–2), 363–366 (2006). 4. D. B. Migas, V. L. Shaposhnikov, and V. E. Borisenko, “Isostructural BaSi2, BaGe2 and SrGe2: electronic and optical properties,” Phys. Status Solidi 244(7), 2611–2618 (2007). 5. S. Kishino, T. Imai, T. Iida, Y. Nakaishi, M. Shinada, Y. Takanashi, and N. Hamada, “Electronic and optical properties of bulk crystals of semiconducting orthorhombic BaSi2 prepared by the vertical Bridgman method,” J. Alloys Compd. 428(1–2), 22–27 (2007). 6. K. Toh, T. Saito, and T. Suemasu, “Optical absorption properties of BaSi2 epitaxial films grown on a transparent silicon-on-insulator substrate using molecular beam epitaxy,” Jpn. J. Appl. Phys. 50(6R), 068001 (2011). 7. N. A. A. Latiff, T. Yoneyama, T. Shibutami, K. Matsumaru, K. Toko, and T. Suemasu, “Fabrication and characterization of polycrystalline BaSi2 by RF sputtering,” Phys. Status Solidi., C Curr. Top. Solid State Phys. 10(12), 1759–1761 (2013). 8. M. Kumar, N. Umezawa, and M. Imai, “BaSi2 as a promising low-cost, earth-abundant material with large optical activity for thin-film solar cells: A hybrid density functional study,” Appl. Phys. Express 7(7), 071203 (2014). 9. K. O. Hara, Y. Nakagawa, T. Suemasu, and N. Usami, “Simple vacuum evaporation route to BaSi2 thin films for solar cell applications,” Procedia Eng. 141, 27–31 (2016). 10. R. Vismara, O. Isabella, and M. Zeman, “Organometallic Halide Perovskite/Barium Di-Silicide Thin-Film Double-Junction Solar Cells,” Proc. SPIE 9898, 98980J (2016). 11. M. Baba, K. Toh, K. Toko, N. Sato, N. Yoshizawa, K. Jiptner, T. Sekiguchi, K. O. Hara, N. Usami, and T. Suemasu, “Investigation of grain boundaries in BaSi2 epitaxial films on Si(111) substrates using transmission electron microscopy and electron-beam-induced current technique,” J. Cryst. Growth 348(1), 75–79 (2012). 12. M. Baba, K. Ito, W. Du, T. Sanai, K. Okamoto, K. Toko, S. Ueda, Y. Imai, A. Kimura, and T. Suemasu, “Hard x-ray photoelectron spectroscopy study on valence band structure of semiconducting BaSi2,” J. Appl. Phys. 114(12), 123702 (2013). 13. K. O. Hara, N. Usami, K. Nakamura, R. Takabe, M. Baba, K. Toko, and T. Suemasu, “Determination of bulk minority-carrier lifetime in BaSi2 earth-abundant absorber films by utilizing a drastic enhancement of carrier lifetime by post-growth annealing,” Appl. Phys. Express 6(11), 112302 (2013). 14. USGS, “Rare earth elements-Critical resources for high technology,” http://pubs.usgs.gov/fs/2002/fs087-02/. 15. ANSYS white paper, “ANSYS HFSS,” http://www.ansys.com/Products/Electronics/ANSYS-HFSS. 16. O. Isabella, S. Solntsev, D. Caratelli, and M. Zeman, “3-D optical modeling of thin-film silicon solar cells on diffraction gratings,” Prog. Photovolt. Res. Appl. 21(1), 94–108 (2013). 17. M. Zeman, O. Isabella, S. Solntsev, and K. Jäger, “Modelling of thin-film silicon solar cells,” Sol. Energy Mater. Sol. Cells 119, 94–111 (2013). Vol. 25, No. 8 | 17 Apr 2017 | OPTICS EXPRESS A402 #283809 https://doi.org/10.1364/OE.25.00A402 Journal © 2017 Received 28 Dec 2016; revised 21 Mar 2017; accepted 21 Mar 2017; published 3 Apr 2017 18. O. Isabella, H. Sai, M. Kondo, and M. Zeman, “Full-wave optoelectrical modeling of optimized flattened light scattering substrate for high efficiency thin-film silicon solar cells,” Prog. Photovolt. Res. Appl. 22(6), 671–689 (2014). 19. C. Onwudinanti, R. Vismara, O. Isabella, L. Grenet, F. Emieux, and M. Zeman, “Advanced light management based on periodic textures for Cu(In,Ga)Se2 thin-film solar cells,” Opt. Express 24(6), A693–A707 (2016). 20. NREL, “Reference solar spectral irradiance: air mass 1.5,” http://rredc.nrel.gov/solar/spectra/am1.5/. 21. M. A. Green, “Lambertian light trapping in textured solar cells and light-emitting diodes: analytical solutions,” Prog. Photovolt. Res. Appl. 10(4), 235–241 (2002). 22. T. Tiedje, E. Yablonovitch, G. D. Cody, and B. G. Brooks, “Limiting efficiency of silicon solar cells,” IEEE Trans. Electron Dev. 31(5), 711–716 (1984). 23. Z. Yu, A. Raman, and S. Fan, “Fundamental limit of light trapping in grating structures,” Opt. Express 18(S3 Suppl 3), A366–A380 (2010). 24. W. Shockley and H. J. Queisser, “Detailed balance limit of efficiency of p-n junction solar cells,” J. Appl. Phys. 32(3), 510–519 (1961). 25. Z. Yu, M. Leilaeioun, and Z. Holman, “Selecting tandem partners for silicon solar cells,” Nat. Energ. 1(11), 16137 (2016). 26. K. X. Wang, Z. Yu, V. Liu, Y. Cui, and S. Fan, “Absorption enhancement in ultrathin crystalline silicon solar cells with antireflection and light-trapping nanocone gratings,” Nano Lett. 12(3), 1616–1619 (2012). 27. O. Isabella, A. Ingenito, D. Linssen, and M. Zeman, “Front/rear decoupled texturing in refractive and diffractive regimes for ultra-thin silicon-based solar cells,” in OSA Technical Digest (2013), paper PM4C.2. 28. S. Yachi, R. Takabe, H. Takeuchi, K. Toko, and T. Suemasu, “Effect of amorphous Si capping layer on the hole transport properties of BaSi2 and improved conversion efficiency approaching 10% in p-BaSi2/n-Si solar cells,” Appl. Phys. Lett. 109(7), 072103 (2016). 29. B. Hoex, S. B. S. Heil, E. Langereis, M. C. M. van de Sanden, and W. M. M. Kessels, “Ultralow surface recombination of c-Si substrates passivated by plasma-assisted atomic layer deposited Al2O3,” Appl. Phys. Lett. 89(4), 042112 (2006). 30. H. Tan, P. Babal, M. Zeman, and A. H. M. Smets, “Wide bandgap p-type nanocrystalline silicon oxide as window layer for high performance thin-film silicon multi-junction solar cells,” Sol. Energy Mater. Sol. Cells 132, 597–605 (2015). 31. V. Demontis, C. Sanna, J. Melskens, R. Santbergen, A. H. M. Smets, A. Damiano, and M. Zeman, “The role of oxide interlayers in back reflector configurations for amorphous silicon solar cells,” J. Appl. Phys. 113(6), 064508 (2013). 32. A. Ingenito, O. Isabella, and M. Zeman, “Experimental demonstration of 4n classical absorption limit in nanotextured ultrathin solar cells with dielectric omnidirectional back reflector,” ACS Photonics 1(3), 270–278 (2014). 33. A. Ingenito, S. L. Luxembourg, P. Spinelli, J. Liu, J. C. O. Lizcano, A. W. Weeber, O. Isabella, and M. Zeman, “Optimized metal-free back reflectors for high-efficiency open rear c-Si solar cells,” IEEE J. Photovolt. 6(1), 34–40 (2016).