Progress in Low-temperature Surface Passivation of Silicon Solar Cells using Remote-plasma Silicon Nitride
✍ Scribed by Armin G. Aberle; Rudolf Hezel
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 391 KB
- Volume
- 5
- Category
- Article
- ISSN
- 1062-7995
No coin nor oath required. For personal study only.
✦ Synopsis
Using a remote-plasma technique as opposed to the conventional direct-plasma technique, signi®cant progress has been obtained at ISFH in the area of lowtemperature surface passivation of p-type crystalline silicon solar cells by means of silicon nitride (SiN) ®lms fabricated at 350±4008C in a plasma-enhanced chemical vapour deposition system. If applied to the rear surface of the low-resistivity p-type substrates, the remote-plasma SiN ®lms provide outstanding surface recombination velocities (SRVs) as low as 4 cm s À1 , which is by a clear margin the lowest value ever obtained on a low-resistivity p-Si wafer passivated by a solid ®lm, including highest quality thermal oxides. Compared to direct-plasma SiN ®lms or thermally grown oxides, the remote-plasma ®lms not only provide signi®cantly better SRVs on lowresistivity p-silicon wafers, but also an enormously improved stability against ultraviolet (UV) light. The potential of these remote-plasma silicon nitride ®lms for silicon solar cell applications is further increased by the fact that they provide a surface passivation on phosphorus-diused emitters which is comparable to highquality thermal oxides. Furthermore, if combined with a thermal oxide and a caesium treatment, the ®lms induce a UV-stable inversion-layer emitter of outstanding electronic quality.
Due to the low deposition temperature and the high refraction index, these remoteplasma SiN ®lms act as highly ecient surface-passivating antire¯ection coatings. Application of these ®lms to cost-eective silicon solar cell designs presently under development at ISFH turned out to be most successful, as demonstrated by diused p-n junction cells with eciencies above 19%, by bifacial p-n junction cells with front and rear eciencies above 18%, by mask-free evaporated p-n junction cells with eciencies above 18% and by MIS inversion-layer cells with a new record eciency of above 17%. All cells are found to be stable during a UV test corresponding to more than 4 years of glass-encapsulated outdoor operation.