140
with PDMS nanocone AR film. For CdS/CdTe device, the J sc improvement is almost
1.11 mA/cm
2
(4.6% enhancement) [33]. It is worth pointing out that the light
absorption in device with nanocone AR layer for angular incidence is significantly
improved as compared to device without AR film. The inset graph in Fig. 5f depicts
the reflectance spectra of CdS/CdTe solar cells without and with PDMS nanocone
for light incident angles changed from 0
°
to 60° using an integrating sphere. From
these results, the nanocone sample remains invariant. The measured J sc under this
condition also confirmed the advantage of nanocone AR film. In nanocone sample,
the J sc enhancement by changing the angle from 0° to 60° is increased as compared
to planar one indicating the advantage of nanocone AR film particularly at larger
angles. This characteristic from nanocone array is beneficial for the solar cells
installed in a solar farm due to the variation of incident sun light during the daytime
and different seasons [33].
The AR films can be used to improve the optical absorption in different types of
solar cell devices. Organo-metal halide perovskite materials have attracted tremendous attention of many research groups due to their interesting properties such as
low-cost fabrication and materials, long carrier diffusion length, high mobility, and
high optical absorption [36]. These properties make them ideal candidates for fabrication of highly efficient solar cell devices with PCE of over 25% [37]. There are a
number of different processes reported for the fabrication of perovskite films such
as spin-coating, deep-coating, vacuum deposition, spray coating, and chemical
vapor deposition [38].
These fabrication methods require low temperature and thus this material has a
great potential for fabrication of flexible solar cells. The application of AR film on
perovskite solar cell has been also studied to decrease the reflectance and further
improve the device performance. The absorption and reflectance spectra of
perovskite films (400 nm-thick) without and with nanocone AR films based on different aspect ratios can be found in Fig. 6a. In fact, by applying the AR film, the
reflectance is decreased and as shown, this reduction is the highest for nanocone
with aspect ratio of 1, indicating the importance of geometry optimization. The
integrated absorption of perovskite films without and with AR film versus different
angles of the incident light indicates unchanged light absorption for nanoconebased device at high angles as compared to device without nanocone (Fig. 6b). In
addition, the contact angle measurement of water droplet on top of nanocone array
demonstrates the excellent superhydrophobicity property of nanocone AR film with
aspect ratio of 1.0 (Fig. 6c). This indicates that by inserting nanocone AR film, the
perovskite solar cells can have self-cleaning property, which is beneficial for industrial applications (Fig. 6d). Since the perovskite films are highly sensitive to moisture, these AR films can increase the stability of devices, which is the main
challenging issue for this type of solar cell [39].
The FDTD simulations for perovskite solar cells without and with nanocone AR
film are shown in Fig. 6e, f. The generation rate profile in both cases can be observed
in the cross-sectional views of the perovskite films, where the electromagnetic plane
waves propagated upward to simulate the real situation. The focal point in the film
with nanocone AR film (reddish colored zone) represents the region with a high
M. M. Tavakoli
with PDMS nanocone AR film. For CdS/CdTe device, the J sc improvement is almost
1.11 mA/cm
2
(4.6% enhancement) [33]. It is worth pointing out that the light
absorption in device with nanocone AR layer for angular incidence is significantly
improved as compared to device without AR film. The inset graph in Fig. 5f depicts
the reflectance spectra of CdS/CdTe solar cells without and with PDMS nanocone
for light incident angles changed from 0
°
to 60° using an integrating sphere. From
these results, the nanocone sample remains invariant. The measured J sc under this
condition also confirmed the advantage of nanocone AR film. In nanocone sample,
the J sc enhancement by changing the angle from 0° to 60° is increased as compared
to planar one indicating the advantage of nanocone AR film particularly at larger
angles. This characteristic from nanocone array is beneficial for the solar cells
installed in a solar farm due to the variation of incident sun light during the daytime
and different seasons [33].
The AR films can be used to improve the optical absorption in different types of
solar cell devices. Organo-metal halide perovskite materials have attracted tremendous attention of many research groups due to their interesting properties such as
low-cost fabrication and materials, long carrier diffusion length, high mobility, and
high optical absorption [36]. These properties make them ideal candidates for fabrication of highly efficient solar cell devices with PCE of over 25% [37]. There are a
number of different processes reported for the fabrication of perovskite films such
as spin-coating, deep-coating, vacuum deposition, spray coating, and chemical
vapor deposition [38].
These fabrication methods require low temperature and thus this material has a
great potential for fabrication of flexible solar cells. The application of AR film on
perovskite solar cell has been also studied to decrease the reflectance and further
improve the device performance. The absorption and reflectance spectra of
perovskite films (400 nm-thick) without and with nanocone AR films based on different aspect ratios can be found in Fig. 6a. In fact, by applying the AR film, the
reflectance is decreased and as shown, this reduction is the highest for nanocone
with aspect ratio of 1, indicating the importance of geometry optimization. The
integrated absorption of perovskite films without and with AR film versus different
angles of the incident light indicates unchanged light absorption for nanoconebased device at high angles as compared to device without nanocone (Fig. 6b). In
addition, the contact angle measurement of water droplet on top of nanocone array
demonstrates the excellent superhydrophobicity property of nanocone AR film with
aspect ratio of 1.0 (Fig. 6c). This indicates that by inserting nanocone AR film, the
perovskite solar cells can have self-cleaning property, which is beneficial for industrial applications (Fig. 6d). Since the perovskite films are highly sensitive to moisture, these AR films can increase the stability of devices, which is the main
challenging issue for this type of solar cell [39].
The FDTD simulations for perovskite solar cells without and with nanocone AR
film are shown in Fig. 6e, f. The generation rate profile in both cases can be observed
in the cross-sectional views of the perovskite films, where the electromagnetic plane
waves propagated upward to simulate the real situation. The focal point in the film
with nanocone AR film (reddish colored zone) represents the region with a high
M. M. Tavakoli