Excellent boron emitter passivation for high‐efficiency Si wafer solar cells using AlO_x/SiN_x dielectric stacks deposited in an industrial inline plasma reactor

Abstract

Excellent passivation of boron emitters is realised using AlOx/SiNx dielectric stacks deposited in an industrial inline plasma‐enhanced chemical vapour deposition reactor. Very low emitter saturation current density (J0e) values of 10 and 45 fA/cm2 are obtained for 180 and 30 Ω/sq planar p+ emitters, respectively. For textured p+ emitters, the J0e was found to be 1.5–2 times higher compared with planar emitters. The required thermal activation of the AlOx films is performed in a standard industrial fast‐firing furnace, making the developed passivation stack industrially viable. We also show that an AlOx thickness of 5 nm in the AlOx/SiNx stack is sufficient for obtaining a J0e of 18 fA/cm2 for planar 80 Ω/sq p+ emitters, which corresponds to a 1‐sun open‐circuit voltage limit of the solar cell of 736 mV at 25 °C. Copyright © 2012 John Wiley & Sons, Ltd.

The Influence of Orientation and Morphology on the Passivation of Crystalline Silicon Surfaces by Al2O3

“…4 are in broad agreement with the previous work of [11] and [12]. Their ranges of 1.5 to 2.0, and 1.7 to 2.5 for the ratio of J 0 at textured and planar <100> surfaces may be compared with the range of 2.0 to 3.3 measured here.…”

“…Duttagupta et al [11] measured the passivation quality of plasma-enhanced chemical vapour deposition (PECVD) Al 2 O 3 /SiN x stacks on borondiffused textured and planar <100> samples, reporting a textured-to-planar J 0 ratio of 1.5-2. A similar experiment was performed by [12] with both Al 2 O 3 /SiN x stacks and Al 2 O 3 by itself, where the Al 2 O 3 was deposited by plasmaassisted ALD.…”

“…They reported a textured-to-planar J 0 ratio between 1.7 and 2.5. However, neither [11] nor [12] included a comparison to planar <111> surfaces, which leaves the role played by the <111> surface orientation of the textured surface open to speculation.…”

Effect of boron concentration on recombination at the p-Si–Al2O3 interface

“…Even lower values of J 0 , down to less than 10 fA/cm 2 , have been reported for Al 2 O 3 from plasma-assisted ALD and plasma-enhanced chemical vapour deposition (PECVD). [23][24][25]27,28,36 B. Determination of S eff from J 0 data…”

Extraction of Surface Recombination Velocity at Highly Doped Silicon Surfaces Using Electron-Beam-Induced Current

“…2 illustrates a schematic of the cross section of the solar cell sample, which consists of a boron-doped p + emitter and a phosphorous-doped n + back-surface field with sheet resistances of 65 and 30 Ω/square, respectively. Both the front and back surfaces of the solar cells were passivated using a stack of aluminum oxide (AlO x ) and silicon nitride (SiN x ) with a combined thickness of 80 nm [16], [17].…”