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Laser fired contacts applied to the rear surface of heterojunction silicon solar cells

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Title: Laser fired contacts applied to the rear surface of heterojunction silicon solar cells
Authors: Martin, I.1 isidro.martin@upc.edu, Labrune, M.2,3, Salomon, A.3, Roca i Cabarrocas, P.2, Alcubilla, R.1
Source: Solar Energy Materials & Solar Cells. Nov2011, Vol. 95 Issue 11, p3119-3123. 5p.
Subjects: Heterojunctions, Silicon solar cells, Microfabrication, Amorphous substances, Electric potential, Electroluminescence, Laser peening, Semiconductor doping
Abstract: Abstract: In this work, we fabricate heterojunction silicon solar cells on p-type substrates whose rear surface configuration is based on dielectric passivation and laser fired contacts (LFC cells). This is an alternative to boron-doped amorphous silicon film, with which we also fabricate solar cells for direct comparison (HJ cells). As substrates, 3.5 and 0.8Ωcm p-type double-side polished FZ c-Si wafers are used. Regarding surface passivation for highly doped substrates, LFC configuration has some advantage due to the higher difficulty in creating an efficient amorphous back surface field. Additionally, those substrates are also more advantageous in terms of carrier injection when the rear surface is locally contacted. Thus LFC cells made on 0.8Ωcm substrates reach V oc values up to 680mV, in the same range as that of their HJ cell counterpart, with better FF demonstrating that LFC configuration is a feasible alternative for highly doped substrates. Focusing on the impact of the distance between rear contacts on cell performance, we found a trade-off between open circuit voltage V oc and fill factor FF. Finally electroluminescence characterization and the dependence of V oc on pitch, modeled by Fischer''s equation, indicate that the depassivated area due to the laser processing of the contacts is bigger than the contacted area. [Copyright &y& Elsevier]
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Database: Engineering Source
Description
Abstract:Abstract: In this work, we fabricate heterojunction silicon solar cells on p-type substrates whose rear surface configuration is based on dielectric passivation and laser fired contacts (LFC cells). This is an alternative to boron-doped amorphous silicon film, with which we also fabricate solar cells for direct comparison (HJ cells). As substrates, 3.5 and 0.8Ωcm p-type double-side polished FZ c-Si wafers are used. Regarding surface passivation for highly doped substrates, LFC configuration has some advantage due to the higher difficulty in creating an efficient amorphous back surface field. Additionally, those substrates are also more advantageous in terms of carrier injection when the rear surface is locally contacted. Thus LFC cells made on 0.8Ωcm substrates reach V oc values up to 680mV, in the same range as that of their HJ cell counterpart, with better FF demonstrating that LFC configuration is a feasible alternative for highly doped substrates. Focusing on the impact of the distance between rear contacts on cell performance, we found a trade-off between open circuit voltage V oc and fill factor FF. Finally electroluminescence characterization and the dependence of V oc on pitch, modeled by Fischer''s equation, indicate that the depassivated area due to the laser processing of the contacts is bigger than the contacted area. [Copyright &y& Elsevier]
ISSN:09270248
DOI:10.1016/j.solmat.2011.06.049