TY - JOUR
T1 - Plasmonic degradation and the importance of over-coating metal nanoparticles for a plasmonic solar cell
AU - Yang, Y.
AU - Pillai, S.
AU - Mehrvarz, H.
AU - Green, M. A.
PY - 2014/3
Y1 - 2014/3
N2 - Plasmonics is an emerging area of study for photovoltaic applications.
The last decade has seen an increasing interest in the application of
metal nanoparticles (MNP) on the surface of solar cells to scatter light
and subsequently achieve light trapping. In this study we investigate
the optical effects of single and double layer rear light trapping
reflectors – planar or scattering; direct or detached, which are
fabricated on the 400 μm front-planar silicon solar cells. As a single
layer reflecting scheme, we find that Ag metal nanoparticles (Ag MNP) as
a scattering reflector outperforms all other single layer reflectors
with a maximum current enhancement of 11% (calculated from 900 nm to 1200 nm)
compared to metal back reflectors. However over time we notice that the
scattering properties are dampened due to tarnishing of the silver
nanoparticles. A double layer reflecting scheme using optimised Ag
nanoparticles as the first layer and the second layer of evaporated Ag
(E Ag) separated via MgF2 is introduced to overcome this issue together with additional light trapping. We find that no EQE or current degradation is observed over time. More importantly, after optimising the over-coating MgF2 thickness, the best-performing double layer reflector structure improves EQE by 4.5-fold at 1160 nm and enhances photocurrent by 25.6% (calculated from 900 nm to 1200 nm),
compared to cells with metal back reflectors. We also conclude that the
optimum thickness of the over-coating layer is dependent on the
wavelength to be optimised, the angular distribution of the plasmonic
nanoparticles scattering within the layer, and the type of adjacent
metal reflector used. It performs best when condition for constructive
interference or enhanced electric field at the rear Si interface is
satisfied. An enhancement of effective optical path length factor Z
of around 9-fold compared to an Al reflector is achieved by using the
optimised double layer reflector, higher than the 6-fold enhancement
reported previously.
AB - Plasmonics is an emerging area of study for photovoltaic applications.
The last decade has seen an increasing interest in the application of
metal nanoparticles (MNP) on the surface of solar cells to scatter light
and subsequently achieve light trapping. In this study we investigate
the optical effects of single and double layer rear light trapping
reflectors – planar or scattering; direct or detached, which are
fabricated on the 400 μm front-planar silicon solar cells. As a single
layer reflecting scheme, we find that Ag metal nanoparticles (Ag MNP) as
a scattering reflector outperforms all other single layer reflectors
with a maximum current enhancement of 11% (calculated from 900 nm to 1200 nm)
compared to metal back reflectors. However over time we notice that the
scattering properties are dampened due to tarnishing of the silver
nanoparticles. A double layer reflecting scheme using optimised Ag
nanoparticles as the first layer and the second layer of evaporated Ag
(E Ag) separated via MgF2 is introduced to overcome this issue together with additional light trapping. We find that no EQE or current degradation is observed over time. More importantly, after optimising the over-coating MgF2 thickness, the best-performing double layer reflector structure improves EQE by 4.5-fold at 1160 nm and enhances photocurrent by 25.6% (calculated from 900 nm to 1200 nm),
compared to cells with metal back reflectors. We also conclude that the
optimum thickness of the over-coating layer is dependent on the
wavelength to be optimised, the angular distribution of the plasmonic
nanoparticles scattering within the layer, and the type of adjacent
metal reflector used. It performs best when condition for constructive
interference or enhanced electric field at the rear Si interface is
satisfied. An enhancement of effective optical path length factor Z
of around 9-fold compared to an Al reflector is achieved by using the
optimised double layer reflector, higher than the 6-fold enhancement
reported previously.
KW - Plasmonic degradation
KW - Rear reflectors
KW - Plasmonic solar cells
KW - Light trapping
UR - http://www.scopus.com/inward/record.url?scp=84891786251&partnerID=8YFLogxK
U2 - 10.1016/j.solmat.2013.12.009
DO - 10.1016/j.solmat.2013.12.009
M3 - Article
AN - SCOPUS:84891786251
SN - 0927-0248
VL - 122
SP - 208
EP - 216
JO - Solar Energy Materials and Solar Cells
JF - Solar Energy Materials and Solar Cells
ER -