| Abstract |
The scope of this diploma thesis is to examine the addition of a 2D material,
Tungsten Disulfide (WS2) with and without gold nanoparticles (Au NPs),into the active
layer (AL) of an Organic bulk-heterojunction (BHJ) Photovoltaic (OPV) device.
Relatively, narrow spectral overlap of organic polymer absorption bands within the
solar spectrum and morphology are two of the major limitations of organic solar cells.
Among different strategies that are in progress to tackle this restriction, the novel
concept of Ternary OPV is a promising strategy to extend the absorption spectra of
large bandgap polymers to the near IR region and to enhance light harvesting in single
bulk-heterojunction solar cells. By using the laser ablation method, Au NPs are formed
into liquids with pico- and femto-second laser pulses and be implanted with WS2
nanosheets (NS). It is found that the laser induced anchoring of Au NPs onto NS basal
plane and edges resulted in enhanced light harvesting that is potentially useful for
energy conversion and storage applications. Due to the perfect energy level matching
of WS2 and the polymer blend, excitons can be efficient dissociate at the interfaces of
Donor (low electron affinity)-Acceptor (high electron affinity) and thus electrons can
be efficiently transported to the negative Aluminum electrode. Enhancement of the
efficiency of bulk heterojunction (BHJ) Polymer-Fullerene devices is demonstrated
first by the addition of WS2 and then WS2-Au NPs solutions in the active layer of the
devices. The power conversion efficiency (PCE) of the binary device consisting of a
poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-
benzothiadiazole)] (PCDTBT) : [6,6]-phenyl-C71-butyric-acid methyl-ester (PC71BM)
blend as the donor-acceptor pair was 5.6%. A significant enhancement of 8% was
achieved reaching 6.1% after the employment of WS2NS (PCDTBT:WS2:PC71BM), while
the incorporation of Au NPs decorated WS2NS (PCDTBT:WS2–Au NPs:PC71BM) further
improved by 12.5% the Power Convention Efficiency (PCE), reaching 6.3%.The
efficiency enhancement can be attributed to light scattering of the large diameter
WS2 NS, improving the absorption spectra inside the photoactive layer and as well as
to better charge transport properties of the ternary blend in the case of the undoped
WS2 blend. On the other hand, the enhancement of performance of devices with Au
NPs doped WS2 ternary blends, can be also attributed further increased absorption
due to the effects of the phenomenon of Localized Surface Plasmon Resonance (L
effects of the small diameter Au NPs.SPR)
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2D Materials and their application in Ternary Organic Photovoltaic Devices
