Global InformationHeterojunction solar cell information
Heterojunction solar cells (HJT), variously known as Silicon heterojunctions (SHJ) or Heterojunction with Intrinsic Thin Layer (HIT),[1] are a family of photovoltaic cell technologies based on a heterojunction formed between semiconductors with dissimilar band gaps. They are a hybrid technology, combining aspects of conventional crystalline solar cells with thin-film solar cells.
Silicon heterojunction-based solar panels are commercially mass-produced for residential and utility markets. As of 2023, Silicon heterojunction architecture has the highest cell efficiency for commercial-sized silicon solar cells.[2] In 2022–2024, SHJ cells are expected to overtake Aluminium Back surface field (Al-BSF) solar cells in market share to become the second-most adopted commercial solar cell technology after PERC/TOPCon (Passivated Emitter Rear Cell/Tunnel Oxide Passivated Contact), increasing to nearly 20% by 2032.[3]
Solar cells operate by absorbing light, exciting the absorber. This creates electron–hole pairs that must be separated into electrons (negative charge carriers) and holes (positive charge carriers) by asymmetry in the solar cell, provided through chemical gradients[4] or electric fields in semiconducting junctions.[5] After splitting, the carriers travel to opposing terminals of the solar cell that have carrier-discriminating properties (known as selective contacts).[6] For solar cells to operate efficiently, surfaces and interfaces require protection from passivation to prevent electrons and holes from being trapped at surface defects, which would otherwise increase the probability of mutual annihilation of the carriers (recombination).
SHJ cells generally consist of an active crystalline silicon absorber substrate which is passivated by a thin layer of hydrogenated intrinsic amorphous silicon (denoted as a-Si:H; the "buffer layer"), and overlayers of appropriately doped amorphous or nanocrystalline silicon selective contacts. The selective contact material and the absorber have different band gaps, forming the carrier-separating heterojunctions that are analogous to the p-n junction of traditional solar cells. The high efficiency of heterojunction solar cells is owed mostly to the excellent passivation qualities of the buffer layers,[7][8][9][10] particularly with respect to separating the highly recombination-active metallic contacts from the absorber.[11] Due to their symmetrical structure, SHJ modules commonly have a bifaciality factor over 90%.[12]
As the thin layers are usually temperature sensitive, heterojunction cells are constrained to a low-temperature manufacturing process.[13][14] This presents challenges for electrode metallisation, as the typical silver paste screen printing method requires firing at up to 800 °C;[15] well above the upper tolerance for most buffer layer materials. As a result, the electrodes are composed of a low curing temperature silver paste, or uncommonly[3] a silver-coated copper paste or electroplated copper.
- ^ Dupré, Olivier; Vaillon, Rodolphe; Green, Martin A. (2017). Thermal Behavior of Photovoltaic Devices. Cham: Springer International Publishing. doi:10.1007/978-3-319-49457-9. ISBN 978-3-319-49456-2.
- ^ Bellini, Emiliano (21 November 2022). "Longi claims world's highest efficiency for silicon solar cells". pv magazine. Retrieved 3 January 2023.
- ^ a b Fischer, Markus; Woodhouse, Michael; Herritsch, Susanne; Trube, Jutta (2022). International Technology Roadmap for Photovoltaic (ITRPV) (13 ed.). Frankfurt, Germany: VDMA e. V. Archived from the original on 2021-02-25. Retrieved 2023-01-08.
- ^ Lipovšek, Benjamin; Smole, Franc; Topič, Marko; Humar, Iztok; Sinigoj, Anton Rafael (2019-05-01). "Driving forces and charge-carrier separation in p-n junction solar cells". AIP Advances. 9 (5). Bibcode:2019AIPA....9e5026L. doi:10.1063/1.5092948. ISSN 2158-3226.
- ^ Green, Martin A. (1982). Solar Cells: Operating Principles, Technology and System Applications. University of New South Wales. ISBN 9780858235809. OSTI 6051511.
- ^ Wang, Guangyi; Zhang, Chenxu; Sun, Heng; Huang, Zengguang; Zhong, Sihua (2021-11-01). "Understanding and design of efficient carrier-selective contacts for solar cells". AIP Advances. 11 (11). Bibcode:2021AIPA...11k5026W. doi:10.1063/5.0063915. ISSN 2158-3226.
- ^ Descoeudres, A.; Barraud, L.; De Wolf, Stefaan; Strahm, B.; Lachenal, D.; Guérin, C.; Holman, Z. C.; Zicarelli, F.; Demaurex, B.; Seif, J.; Holovsky, J.; Ballif, C. (2011). "Improved amorphous/crystalline silicon interface passivation by hydrogen plasma treatment" (PDF). Applied Physics Letters. 99 (12): 123506. Bibcode:2011ApPhL..99l3506D. doi:10.1063/1.3641899.
- ^ Olibet, Sara; Vallat-Sauvain, Evelyne; Ballif, Christophe (July 2007). "Model for a-Si:H/c-Si interface recombination based on the amphoteric nature of silicon dangling bonds". Physical Review B. 76 (3): 035326. Bibcode:2007PhRvB..76c5326O. doi:10.1103/PhysRevB.76.035326.
- ^ Taguchi, Mikio; Terakawa, Akira; Maruyama, Eiji; Tanaka, Makoto (2005). "Obtaining a higher VOC in HIT cells". Progress in Photovoltaics: Research and Applications. 13 (6): 481–488. doi:10.1002/pip.646. S2CID 97445752.
- ^ Zhang, D.; Tavakoliyaraki, A.; Wu, Y.; van Swaaij, R.A.C.M.M.; Zeman, M. (2011). "Influence of ITO deposition and post annealing on HIT solar cell structures". Energy Procedia. 8: 207–213. doi:10.1016/j.egypro.2011.06.125. ISSN 1876-6102.
- ^ Cite error: The named reference
dewolf2012was invoked but never defined (see the help page). - ^ Cite error: The named reference
:14was invoked but never defined (see the help page). - ^ De Wolf, Stefaan; Kondo, Michio (2009). "Nature of doped a-Si:H/c-Si interface recombination". Journal of Applied Physics. 105 (10): 103707–103707–6. Bibcode:2009JAP...105j3707D. doi:10.1063/1.3129578.
- ^ Descoeudres, A.; Allebé, C. (2018). "Low-temperature processes for passivation and metallization of high-efficiency crystalline silicon solar cells". Solar Energy. 175: 54–59. Bibcode:2018SoEn..175...54D. doi:10.1016/j.solener.2018.01.074. ISSN 0038-092X. S2CID 125737077.
- ^ Wright, Matthew; Kim, Moonyong; Dexiang, Peng; Xin, Xu; Wenbin, Zhang; Wright, Brendan; Hallam, Brett (2019). "Multifunctional process to improve surface passivation and carrier transport in industrial n-type silicon heterojunction solar cells by 0.7% absolute". 15th International Conference on Concentrator Photovoltaic Systems (CPV-15). Vol. 2149. Fes, Morocco. p. 110006. doi:10.1063/1.5123882. S2CID 202990239.
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