Surface and bulk passivation of multicrystalline silicon solar cells by ...

LIST OF FIGURES
(Continued)
Figure
Page
3.9 Calculated dependence of surface recombination velocity (Ss) for (a) n-Si and
(b) p-Si surfaces as a function of injection level (Δn) for different fixed positive
charge densities and interface state densities, σn= 10 14 cm 2 and σp= 10-16 16
cm-2 56
3.10 Measured effective SRV showing dependence on excess carrier density [89]
57
3.11 High-resolution cross-sectional TEM of Si-SiΝx :Η interface before firing
showing process-induced damage by plasma [92] 58
3.12 Calculated recombination velocity, components S S and SSCR (dotted lines), and
the total Seff (solid lines) at SiΝx :Η/Si interface as a function of injection level.
Assumptions: p-Si, 1.5 Ωcm, Q = 2x 1012cm-2, Dit1=1 x10 12 eV-1cm-2,
D21x10 1 eV-1cm-2 ................... .......................................... .....e.....,. 60
3.13 A schematic illustration of Η transport from SiΝ:Η layer to bulk Si .. 62
3.14 The SIMS profiles of Η in a solar cell introduced during a PECVD SiN coating
before (red line) and after contact annealing (black line) [98] ............ . ........... 63
3.15 Effect of PECVD on the internal quantum efficiency of the cell [99] ............... 64
4.1 A photograph of QSSPCD apparatus at NREL ... 67
4.2 τb of a p-type Si wafer measured by QSSPCD as a function of time. The sample
was cleaned by "ICP" and passivated in IE solution. (A) after ICP; (B) dilute
HF dip after (A); (C) dilute HF dip after (B); (D) after oxidation clean [108] ...... 69
4.3 Time dependence of 'Lb after including oxidation in the cleaning procedure, for
sequential cleaning steps [ 108] ... ........................................ . .. . ..... . . .. 70
4.4 τb decay after light exposure (no rise time was observed) [108] 72
4.5 Short-term variation of τb fora long lifetime wafer. The wafer was cleaned with
the new procedure [ 108] 72
4.6 τb of a p-type wafer, resistivity 27 Ω-cm measured after several treatments: UV
for 15 min and 30 min, heating, exposure to light for different times [108] 73
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