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Detailed Study on the Passivation Mechanism of a-SixC1-x for the Solar Cell Rear Side
D. Suwito, T. Roth, D. Pysch, L. Korte, A. Richter, S. Janz, S.W. Glunz
c-Si, Passivation, a-SiC
Wafer-Based Silicon Solar Cells and Materials Technology
Subtopic: Mono- and Multicrystalline Silicon Cells and Materials, Processing Technology of
Event: 23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain
Session: 2AO.2.3
1023 - 1028
ISBN: 3-936338-24-8
Paper DOI: 10.4229/23rdEUPVSEC2008-2AO.2.3
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Document(s): paper


In this work we focus on the surface passivation of p-FZ, 1 Ωcm silicon wafers by intrinsic, silicon-rich, amorphous silicon carbide (a-SixC1-x:H) with excellent passivation quality (Seff < 5 cms-1 for p- and n-type 1 Ωcm silicon at n=5·1014 cm-3). For the purpose of extracting the effective surface recombination velocity (Seff) independent of the bulk properties, we use a set of identically passivated wafers of different substrate thickness (W). The injection-dependent carrier lifetime eff(n) is determined in a wide injection level range (1010-1017 cm-3) using a combination of the quasi-steady-state photoconductance (QSS-PC) and photoluminescence (QSS-PL) technique. Seff is extracted by evaluation of the slope of the 1/eff vs. 1/W plot for each injection level without any additional assumptions on the bulk lifetime. These pure Seff data obtained in such a way is then used within the simple Shockley-Read-Hall (SRH) model to extract surface parameters such as the interface charge density Qf. Surface photovoltage measurements (SPV) performed on the a-SiC/c-Si system confirm an amphoteric behaviour of the interface charge. Our study shows that the low-injection lifetime data determined by QSS-PL plays a crucial role for the accurate modelling of surface parameters.