The effect of rear surface passivation layer thickness on high efficiency solar cells with planar and scattering metal reflectors

Yang Yang*, Hamid Mehrvarz, Supriya Pillai, Martin Green, Henner Kampwerth, Anita Ho-Baillie

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

1 Citation (Scopus)


Rear surface reflector of solar cell is designed to improve light collection capacity by allowing the low energy photons to go through multiple bounces inside the solar device before escaping. In this paper, we investigate the thickness effect of rear SiO2 surface passivation layer on both optical and electrical properties of front-planar high efficiency PERT (Passivated Emitter and Rear Totally-Diffused) solar cells. Two kinds of metal reflectors are fabricated: the conventional planar reflectors by evaporated Al and the novel scattering reflectors by self assembled Ag nanoparticles. We find that the thickness dependence of rear SiO2 layer (from 8 nm - 134 nm) on photocurrent shows an asymmetry for planar and scattering reflectors, moreover, the scattering reflectors perform much better than the planar reflectors under all tested SiO2 thicknesses. A maximum current enhancement (calculated from wavelength 900 nm to 1200 nm) of 12.1% is presented for planar reflector with 134 nm SiO2 film, and 18.4% for scattering reflector with the optimized 19 nm rear SiO2 film. Additionally, by adding a detached metal mirror, the maximum current enhancement from scattering reflector jumps to 27.0%. Effective optical path length Z is calculated to study the light trapping (optical properties) under various SiO2 thicknesses for both reflectors. Diffusion length L is calculated to track the electrical performance. It is shown that thicker SiO2 is of benefit for both optical and electrical properties when planar Al reflector is used. However, for scattering reflectors, thinner SiO2 is preferable for optical enhancement, but thicker SiO2 is desirable for electrical gain. 19 nm SiO2 is found to be the best choice for cells with scattering reflectors, considering both effects.

Original languageEnglish
Title of host publication2012 38th IEEE Photovoltaic Specialists Conference
Place of PublicationPiscataway, NJ
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Number of pages5
ISBN (Electronic)9781467300667, 9781467300650
ISBN (Print)9781467300643
Publication statusPublished - 2011
Externally publishedYes
Event38th IEEE Photovoltaic Specialists Conference, PVSC 2012 - Austin, TX, United States
Duration: 3 Jun 20128 Jun 2012

Publication series

ISSN (Print)0160-8371
ISSN (Electronic)0160-8371


Conference38th IEEE Photovoltaic Specialists Conference, PVSC 2012
Country/TerritoryUnited States
CityAustin, TX


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