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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Thermally
Stable Solution Processed Vanadium Oxide As A Hole Extraction Layer In Organic
Solar Cells
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رابط إلى البحث:
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Click here
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تاريخ النشر:
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25 March 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 (2):
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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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Click here
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تاريخ النشر:
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27 April 2016
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موجز عن البحث:
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The correlation between cathode work function and open-circuit
voltages (Voc) 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 Jsc 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 Voc 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 Voc 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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The
Royal Society Of Chemistry Annual Meeting
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تاريخ الإنعقاد:
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15 January 2014
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مكان الإنعقاد:
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London,
UK
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طبيعة المشاركة:
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Oral
presentation
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عنوان المشاركة:
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High
Performance Bulk-Heterojunction
Organic
Solar Cell Using Molybdenum (VI) Oxide Bis (2,4-pentanedionate) as a
Precursor for Anode Interfacial Layer
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ملخص المشاركة:
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Polymer-fullerene
bulk heterojunction (BHJ) solar cells have received great attention in the
recent years due to their low-cost, simplicity and feasibility of
roll-to-roll manufacture. One method to reduce the manufacture cost further
is by eliminating the thermal evaporation step for metal oxide using the
analogue solution process. In particular, many studies have been conducted to
synthesis molybdenum precursor that is efficient to produce high quality
thin-film with as low thermal annealing as possible.
We
report the fabrication of BHJ solar cells based on poly[9,9-dioctylfl u-
orene-4,7-alt-(5,6-bis (octyloxy)-4,7-di(2,2 ′ -bithiophen-5-yl) benzo[c][1,2,5]thiadiazole)-5,5-diyl]:(6,6-pheny
C71- butyric acid methyI ester (PFDT2BT-8:PC70BM) as the photoactive layer
and solution-processed MoO3 as the anode interfacial layer. The molybdenum
precursor is simply synthesised by dissolving Molybdenum (VI) Oxide
Bis(2,4-pentanedionate) powder in methanol. The devices hence show
performance that is superior to cells fabricated with evaporated MoO3. The
power conversion efficiency increases from 5.85% to 6.23% by incorporating an
ultrathin molybdenum layer. Such efficiencies are realized without any
necessity for solvent additives or thermal annealing protocols. This enhancement
thus is mainly due to the observed increase in the short circuit current from
9.82 to 10.51 mA/cm3
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المؤتمر (2):
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عنوان المؤتمر:
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International
Conference On Hybrid And Organic Photovoltaics 2015
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تاريخ الإنعقاد:
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10-13 May 2015
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مكان الإنعقاد:
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Rome,
Italy
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طبيعة المشاركة:
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Oral
presentation
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عنوان المشاركة:
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Tuning
of ITO Work Function for Cathode modification in Inverted Polymer Solar Cells
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ملخص المشاركة:
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Appropriate
interfacial modification plays an important role in the high performance of
polymer solar cells. We report the correlation between the changes in the
work function of a transparent cathode of indium tin oxide (ITO) modified
with an ultrathin layer of peptide (biomaterials) and device parameters.
Ultraviolet photoelectron spectroscopy (UPS) indicates the reduction in the
work function of modified electrodes to be in order of 0.3 eV. The inverted
device with the peptide-modified ITO showed significantly resistible loss of
efficiency than non-modified devices. The results provide an environmentally
safe method to fabricate efficient and air-stable polymer solar cells.
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المؤتمر (3):
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عنوان المؤتمر:
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UK
Semiconductors
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تاريخ الإنعقاد:
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1-2nd July 2015
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مكان الإنعقاد:
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Sheffield,
UK
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طبيعة المشاركة:
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Oral
presentation
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عنوان المشاركة:
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Tuning
Of ITO Work Function For Cathode Modification In Inverted Polymer Solar Cells
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ملخص المشاركة:
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Inverted
polymer solar cells (PSCs) have gradually received attention in the recent
years due to their long-term stability. Since an indium tin oxide (ITO) is a
bottom cathode for an electron collection, there can be a serious mismatch
between the ITO work function (anywhere between 5.0 eV and 4.5 eV) and the
lowest unoccupied molecular orbital (LUMO) energy level of organic acceptors.
Therefore, lowering and stabilizing the work function of the ITO could be a
key to realizing highly efficient inverted polymer solar cells. However, less
attention has been devoted to investigate the effect of ITO work function
changes on device parameters; open-circuit voltage (Voc), short-circuit
current (Jsc), fill factor (FF) and power conversion efficiency (PCE).
Herein,
the work function of the ITO was tuned by solution pre-treatments, oxygen
plasma etching, thermal annealing and peptide based self-assembled monolayer
(SAM). Investigation of PCDTBT:PC70BM based inverted solar cells with no
interlayer buffer shows that annealing blank ITO substrates up to 200 C
enhanced both Voc and FF due to the reduction of ITO work function. A maximum
power conversion efficiency of 5.5% was obtained for optimized blank ITO
devices. However, the open-circuit voltage was significantly decreased from
0.90 V to 0.66 V when ITO treated with GlyGly SAM. Having an aromatic ring
within the main-chain of Gly-Phe causes a reduction in Jsc by 19% compared to
blank ITO devices as a result of an increase in the series resistance.
Results suggest that with an appropriate pretreatment, indium tin oxide is an
adequate cathode material for inverted PSCs. However, further investigations
using XPS and UPS are currently ongoing.
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المؤتمر (4):
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عنوان المؤتمر:
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The 9th
Saudi Students Conference
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تاريخ الإنعقاد:
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13 – 14 Feb 2016
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مكان الإنعقاد:
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Birmingham,
UK
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طبيعة المشاركة:
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Oral
presentation
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عنوان المشاركة:
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Tunability
of ITO Work Function by Thermal Annealing for Inverted Organic Photovoltaics
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ملخص المشاركة:
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Organic
photovoltaics (OPVs), the technology that converts sun light into electricity
by employing thin films of organic semiconductors sandwiched between two
conductive electrodes, has been the subject of active research over the past
two decades and has received increased interest in recent years by the
industrial sectors. Organic semiconductors have many advantages compared to
conventional inorganic semiconductors including mechanical flexibility,
lightness, low cost and large-area fabrication. One the other hand, there are
some restrictions to overcome. The power conversion efficiency (PCE) of
standard OPVs is still very low (≤10%) compared to the analogue silicon PVs,
which is attributed to the restricted transport of charge carrier at
electrode/organic layer interfaces. The air stability is also limited by the
rapid oxidation of low-work-function cathode as a result of etching indium
tin oxide (ITO) electrode with poly (3,4-ethylenedioxythiophene):
poly(styrene sulfonate) (PEDOT:PSS) hole-transport layer. Consequently, the device
performance degrades, leading to poor lifetimes. In this communication, we
report the tunability of ITO work function by thermal annealing with no need
for an interlayer insertion. Investigation of PCDTBT: PCBM inverted devices
exhibits that the PCE was significantly reduced from 4.52 % to 3.55 %. An
observation dedicates mainly to the systematic reduction in the open-circuit
voltage (Voc) from 0.88 V to 0.75 V with increasing annealing temperatures.
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المؤتمر (5):
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عنوان المؤتمر:
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EMN
Meeting On Transparent Electrodes
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تاريخ الإنعقاد:
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05-09 December 2016
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مكان الإنعقاد:
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Orlando,
FL USA
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طبيعة المشاركة:
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Oral
Presentation
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عنوان المشاركة:
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Polymer
Solar Cells: how transparent electrodes has contributed to the targeted efficiency
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ملخص المشاركة:
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The
combination of the unique electronic properties as well as the solution
processing, mechanical and effective-cost advantages of conducting polymers
have made them an attractive candidate to compete with the traditional
silicon in photovoltaic devices. It was predicted that efficiencies of 10%
and 15% are possibly obtainable for single and multiple junction polymer
solar cells, respectively. Indeed, highly efficient single junction devices
with over than 10% have been already reported. Thanks for the advanced
technologies in polymer engineering and the discovery of inverted
architecture.
Inverted
polymer solar cells have an upside-down pathway for the photogenerated
electrical current, wherein indium tin oxide (ITO) transparent electrodes
serve as bottom cathodes, collecting the negatively charged carriers. A
significant issue of inverted structure compared to normal structure is the
mismatch between the ITO work function and fullerene LUMO energy levels,
leading to current leakage and reducing the open-circuit voltage. Surface
treatments are therefore needed to achieve the targeted efficiency. Figure 1
shows the timeline of device efficiency evolved upon the application of
different cathode interlayers such as metal oxides, conjugated polymers, and
self-assembled monolayers. In this talk, the contribution of metal oxides,
particularly zinc oxide is critically analyzed.
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