مجال
التميز
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تميز دراسي وبحثي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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Solution processed
nickel oxide anodes for organic photovoltaic devices
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تاريخ النشر:
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11/02/2014
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موجز عن البحث:
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Nickel oxide thin
films have been prepared from a nickel acetylacetonate
(Ni(acac)) precursor for use in bulk heterojunction organic photovoltaic devices. The
conversion of Ni(acac) to NiOx has been investigated. Oxygen plasma
treatment of the NiO layer after annealing at 400 °C affords solar cell
efficiencies of 5.2%. Photoelectron spectroscopy shows that high temperature
annealing converts the Ni(acac) to a reduced form of nickel oxide.
Additional oxygen plasma treatment further oxidizes thesurface layers
and deepens the NiO work function from 4.7 eV for the
annealed film, to 5.0 eV allowing for efficient hole extraction at
the organic interface.
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البحث (2):
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عنوان البحث:
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Intensity-Modulated
Spectroscopy on Loaded Organic Photovoltaic Cells
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تاريخ النشر:
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01/07/2015
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موجز عن البحث:
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We configured a
generic digital lock-in amplifier as a light intensity-modulated spectrometer
for photovoltaic (PV) cells for intensity-modulated spectroscopy (IMS) up to
250 kHz. We performed IMS on a state-of-the-art bulk heterojunction (BHJ)
organic PV (OPV) cell and introduced a new mode of IMS, wherein PV cells work
under finite load, including maximum power point (MPP). Quantitative analysis
supported by equivalent circuit simulations establishes MPP-IMS as favorable
alternative to the commonly used intensity-modulated
photovoltage/photocurrent spectroscopy (IMVS/IMPS) modes. Using IMS under
finite load, we identify a high-frequency feature that is invisible in both
IMPS and IMVS. The feature is ageing-related and becomes more prominent after
long-term storage. We propose an extended equivalent circuit model that
locates the origin of this feature at the BHJ itself and link it to diffusion
of indium ions etched from the transparent electrode by the hole extracting
PEDOT:PSS. Finally, we introduce a method to determine BHJ capacitance by IMS
without absolute calibration of light intensity.
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البحث (3):
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عنوان البحث:
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Thermally Stable
Solution Processed Vanadium Oxide as a Hole Extraction Layer in Organic Solar
Cells
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تاريخ النشر:
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25/03/2016
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موجز عن البحث:
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Low-temperature
solution-processable vanadium oxide (V2Ox) thin films have been employed as
hole extraction layers (HELs) in polymer bulk heterojunction solar cells.
V2Ox films were fabricated in air by spin-coating vanadium(V)
oxytriisopropoxide (s-V2Ox) at room temperature without the need for further
thermal annealing. The deposited vanadium(V) oxytriisopropoxide film
undergoes hydrolysis in air, converting to V2Ox with optical and electronic
properties comparable to vacuum-deposited V2O5. When s-V2Ox thin films were
annealed in air at temperatures of 100 °C and 200 °C, OPV devices showed
similar results with good thermal stability and better light transparency.
Annealing at 300 °C and 400 °C resulted in a power conversion efficiency
(PCE) of 5% with a decrement approximately 15% lower than that of unannealed
films; this is due to the relative decrease in the shunt resistance (Rsh) and
an increase in the series resistance (Rs) related to changes in the oxidation
state of vanadium.
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البحث (4):
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عنوان البحث:
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Open-Circuit
Voltage in Inverted Polycarbazole: Fullerene Bulk Heterojunction Solar Cells
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رابط إلى البحث:
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here
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تاريخ النشر:
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27/04/2016
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موجز عن البحث:
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The correlation
between cathode work function and open-circuit voltages (V _{oc} ) in
inverted polycarbazole:fullerene (PCDTBT:PC70BM) bulk-heterojunction solar
cells has been investigated by postannealing of indium tin oxide (ITO)
electrodes. The ITO function is seen to change from 4.2 to 4.5 eV without the
need to insert additional interfacial layers with annealing temperature up to
400 °C. The best device performance was obtained at room temperature with the
ITO work function of 4.2 eV with a V _{oc}
of 0.89 eV, a J _{sc} of 8.06
mA·cm-2, a fill factor (FF) of 64.70%, and a power conversion efficiency of
4.62%. Together with previously published results, we are able to extract two
regimes of V _{oc} dependence on the
cathode work function: first, a linear relationship when the cathode work
function exceeds the lowest unoccupied molecular orbital (LUMO) of PCBM and,
second, a constant V _{oc} regime when
the ITO work function reduces below the LUMO level. These results provide
general guidelines for the cathode contact design in inverted polymer solar
cells.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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HOPV14
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تاريخ الإنعقاد:
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14/05/2014
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مكان
الإنعقاد:
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Lausanne, Switzerland
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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High performance of
organic solar cells with solution-processed vanadium pentoxide hole
extraction layers
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ملخص المشاركة:
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Vanadium oxide
(s-V2O5) thin films have been employed as a hole extraction layer (HEL) in
polymer bulk heterojunction solar cells (OPV). V2O5 films were fabricated by
a spin-coating solutions of vanadium oxitriisopropoxide precursor at room
temperature in air. Significantly, the deposition method does not requirethermal
annealing or plasma treatment. Absorption spectroscopy shows that s-V2O5
oxide layer is highly transparent (> 97 % for a 4 nm film) in the visible
range with a band gap of 2.75 eV. The electronic structure of s-V2O5 film has
been studied byultraviolet photoelectron spectroscopy and shows a work
function of 5.2 eV resulting in effective hole extraction with minimum
barrier. OPVs withs-V2O5hole extraction layer, and active layer of
PFD2TBT8:PC70BMand an electron extraction layer of Ca show an efficiency of
6.3 (± 0.2) %. A range of alternative hole extraction layers (PEDOT,
thermally deposited V2O5 and MoO3, and solution deposited MoO3) have been
studied with the best competing devices yielding 6.0 (± 0.2) % efficiency. In
addition the lifetime stability of different hole extraction layers devices
under outdoor conditions for 10 weekswill be presented.
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المؤتمر (2):
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عنوان المؤتمر:
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HOPV15
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تاريخ الإنعقاد:
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13/05/2015
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مكان
الإنعقاد:
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Rome, Italy
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Lifetime analysis
and degradation study of OPVs utilising a solution processed V2O5 Intelayer
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ملخص المشاركة:
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In recent years, several studies have shown that
fabrication OPVs with s-V2Ox exhibit high performance which are similar or
better than other devices that utilise different HTLs. However, most of
aqueous metal oxides reported in literature require post-deposition treatment
such as thermal annealing and plasma treatment. Herein we fabricated V2Ox
thin films (5 nm thickness) by a spin-coating solutions of vanadium
oxitriisopropoxide precursor at room temperature in air without any
post-treatment. OPVs incorporating untreated s-V2Ox thin film and active
layer of PFD2TBT8:PC70BM shows efficiency up to 6.5 %. This is comparable to
devices made with a thermally evaporated MoOx or PEDOT:PSS HTL.
However,
preliminary lifetime results of s-V2Ox devices have the shortest lifetime.
Increasing V2Ox layer thickness up to 20 nm with annealing at 110 ℃ for 20
minutes can improve significantly the lifetime to be comparable with other
devices.
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المؤتمر (3):
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عنوان المؤتمر:
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UK Semiconductors
2014
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تاريخ الإنعقاد:
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09/07/2014
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مكان
الإنعقاد:
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Sheffield, UK
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طبيعة المشاركة:
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Paper Presentation
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عنوان المشاركة:
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High performance of
organic solar cells with solution-processed vanadium pentoxide hole
extraction layers
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ملخص المشاركة:
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Vanadium oxide
(s-V2O5) thin films have been employed as a hole extraction layer (HEL) in
polymer bulk heterojunction solar cells (OPV). V2O5 films were fabricated by
a spin-coating solutions of vanadium oxitriisopropoxide precursor at room
temperature in air. Significantly, the deposition method does not
requirethermal annealing or plasma treatment. Absorption spectroscopy shows
that s-V2O5 oxide layer is highly transparent (> 97 % for a 4 nm film) in
the visible range with a band gap of 2.75 eV. The electronic structure of
s-V2O5 film has been studied byultraviolet photoelectron spectroscopy and
shows a work function of 5.2 eV resulting in effective hole extraction with minimum
barrier. OPVs withs-V2O5hole extraction layer, and active layer of
PFD2TBT8:PC70BMand an electron extraction layer of Ca show an efficiency of
6.3 (± 0.2) %. A range of alternative hole extraction layers (PEDOT,
thermally deposited V2O5 and MoO3, and solution deposited MoO3) have been
studied with the best competing devices yielding 6.0 (± 0.2) % efficiency. In
addition the lifetime stability of different hole extraction layers devices
under outdoor conditions for 10 weekswill be presented.
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المؤتمر (4):
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عنوان المؤتمر:
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UK Semiconductors
2015
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تاريخ الإنعقاد:
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01/07/2015
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مكان
الإنعقاد:
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Sheffield, UK
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طبيعة المشاركة:
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Paper Presentation
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عنوان المشاركة:
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Lifetime analysis
and degradation study of OPVs utilising a solution processed V2O5 Intelayer
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ملخص المشاركة:
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In recent years, several studies have shown that
fabrication OPVs with s-V2Ox exhibit high performance which are similar or
better than other devices that utilise different HTLs. However, most of
aqueous metal oxides reported in literature require post-deposition treatment
such as thermal annealing and plasma treatment. Herein we fabricated V2Ox
thin films (5 nm thickness) by a spin-coating solutions of vanadium
oxitriisopropoxide precursor at room temperature in air without any
post-treatment. OPVs incorporating untreated s-V2Ox thin film and active
layer of PFD2TBT8:PC70BM shows efficiency up to 6.5 %. This is comparable to
devices made with a thermally evaporated MoOx or PEDOT: PSS HTL.
However,
preliminary lifetime results of s-V2Ox devices have the shortest lifetime.
Increasing V2Ox layer thickness up to 20 nm with annealing at 110 ℃ for 20
minutes can improve significantly the lifetime to be comparable with other
devices.
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