Nanowires (NW)/nanopillars (NP) have unique optical and electrical properties that make them attractive for
photovoltaic applications. Important factors such as diameter, length and array density of the nanowires have
investigated in the recent years or their effect on light trapping. In this work, we study the effect of varying
the NWs top tip morphology, and find significant differences in optical response, both via simulations and
experiments. In the simulations, optical performance of NW with flat top and spherical top were investigated.
The simulated 3D model is a CNT/Cr/a-Si/ITO coaxial structure with total diameter of 760nm. Our results
show that as the spacing of the NWgets smaller, the influence of the top morphology on the nanowires’ reflectance
becomes more significant. For narrow spacing arrays (p<2d, where p is the period and d is the diameter of NWs)
NW device with spherical top shows better antireflection performance than the one with flat top. This is due to
the biomimetic antireflection (AR) effect introduced by the spherical top . For large spacing arrays (p<2d), AR
effect introduced by spherical tops was almost negligible. It can be ascribed to the low volume concentration
of the spherical top comparing to that of the planar surface. In addition, effect of structural defects were also
Minimizing surface reflection loss is critical when designing high efficiency solar cells. In recent years, biomimetic
antireflection nanostructures (such as moth-eye structures), with their extraordinary broadband and omnidirectional
antireflection properties, have caught much attention. Single side biomimetic antireflection (AR) coatings
show good performance in suppressing broadband reflection between air and glass interface. However, reflection
from the interface between absorption layer and transparent window layer still remains. In this study,
we proposed a double-side gradient-index nanostructure, and examined its reflection spectrum in comparison
with different biomimetic nanostructures using a finite-difference time-domain (FDTD) simulation and effective
medium theory (EMT). In order to minimize surface reflection, all abrupt interfaces were replaced by gradientindex
biomimetic nanostructures, including air/glass interface and absorber/glass interface. Monolayer of silica
spheres serve as double-side gradient-index nanostructures, partially immersed into photoabsorbing material.
Spheres with diameter smaller than incoming light wavelength show excellent antireflection properties. From
simulation results, in normal incidence, average reflection rate of optimized AR coating structure was lower to
around 5% compared to originally above 25% within visible spectrum region (350nm – 850nm). Details of how
to apply such biomimetic nanostructures in thin film solar cells were also discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.