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EnglishIn the literature, the thin buffer layers, used to passivate the junction interface in amorphous silicon / crystalline silicon heterojunction solar cells, are often referred to as intrinsic amorphous layers. However, the optical measurements and high resolution TEM cross section observations show that the so-called i a-Si:H layers, grown on (100) crystalline silicon under the standard PECVD conditions used to deposit good quality amorphous layers on glass, can partially regrow epitaxially on the c-Si substrate. Moreover, when a pyramidal textured c-Si substrate is used, the epitaxial regrowth is much more pronounced compared with a flat c-Si substrate. In this paper, we demonstrate that a partial regrowth is detrimental for the device performance, leading to a degradation of the Voc of the cell with respect to the case where no buffer layer is used. A fully epitaxial buffer layer is shown to improve the interface passivation, and consequently the Voc of the device. Using flat c-Si (CZ grown, 1 ohm.cm) substrates and an amorphous emitter, a 605 mV Voc and a 13.5 % efficiency on 1cm2 cells are obtained. A new hypothesis about the structural nature of the intrinsic 'amorphous' buffer layer used in amorphous silicon / crystalline silicon heterojunction is proposed.
| Titolo: | Heterojunction solar cells: a new insight in the intrinsic buffer layer concept |
| Autore/i: | CENTURIONI, EMANUELE; IENCINELLA, DANIELE; R. RIZZOLI; C. SUMMONTE; DESALVO, AGOSTINO; ZIGNANI, FLAVIO; A. MIGLIORI |
| Autore/i Unibo: | |
| Anno: | 2004 |
| Titolo del libro: | Nineteenth European Photovoltaic Solar Energy Conference |
| Pagina iniziale: | 1285 |
| Pagina finale: | 1288 |
| Abstract: | In the literature, the thin buffer layers, used to passivate the junction interface in amorphous silicon / crystalline silicon heterojunction solar cells, are often referred to as intrinsic amorphous layers. However, the optical measurements and high resolution TEM cross section observations show that the so-called i a-Si:H layers, grown on (100) crystalline silicon under the standard PECVD conditions used to deposit good quality amorphous layers on glass, can partially regrow epitaxially on the c-Si substrate. Moreover, when a pyramidal textured c-Si substrate is used, the epitaxial regrowth is much more pronounced compared with a flat c-Si substrate. In this paper, we demonstrate that a partial regrowth is detrimental for the device performance, leading to a degradation of the Voc of the cell with respect to the case where no buffer layer is used. A fully epitaxial buffer layer is shown to improve the interface passivation, and consequently the Voc of the device. Using flat c-Si (CZ grown, 1 ohm.cm) substrates and an amorphous emitter, a 605 mV Voc and a 13.5 % efficiency on 1cm2 cells are obtained. A new hypothesis about the structural nature of the intrinsic 'amorphous' buffer layer used in amorphous silicon / crystalline silicon heterojunction is proposed. |
| Data prodotto definitivo in UGOV: | 11-ott-2005 |
| Appare nelle tipologie: | 4.01 Contributo in Atti di convegno |
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