Chapters authored
Heterostructures Based on Porphyrin/Phthalocyanine Thin Films for Organic Device Applications
Multilayer or blend heterostructures based on porphyrins and phthalocyanines were obtained on different substrates using VTE and MAPLE methods. Stacked structures based on ZnPc and C60 with NTCDA were prepared by VTE on ITO/glass, their current value being increased by the deposition of the materials in an inverted configuration or by using ITO/PEDOT:PSS as a substrate. Multilayer structures comprising ZnPc and NTCDA were fabricated by MAPLE on an AZO/glass. Treating the AZO in oxygen plasma, a higher current value was obtained for the deposited heterostructures. The oxygen plasma treatment can increase the work function of the AZO resulting in a decrease of the energetic barrier from AZO/organic interface and finally improving the charge transport. Stacked layers or blend heterostructures having ZnPc, MgPc and TPyP were deposited by MAPLE on ITO/PET. In the case of those containing MgPc and TPyP, an increase in the current value (in dark) was obtained for the blend compared to the stacked layer configuration. For those with ZnPc and TPyP, under illumination, a photovoltaic effect was observed for the blend structure. All heterostructures are featured by a large absorption in the visible domain of the solar spectrum and suitable electrical properties for their use in OPV applications.
Part of the book: Phthalocyanines and Some Current Applications
Laser Prepared Thin Films for Optoelectronic Applications
Laser techniques such as pulsed laser deposition, combinatorial pulsed laser deposition, and matrix-assisted pulsed laser evaporation were used to deposit thin films for optoelectronic applications. High-quality transparent conductor oxide films ITO, AZO, and IZO were deposited on polyethylene terephthalate by PLD, an important experimental parameter being the target-substrate distance. The TCO films present a high transparency (>95%) and a reduced electrical resistivity (5 × 10−4 Ωcm) characteristics very useful for their integration in the flexible electronics. InxZn1−xO films with a compositional library were obtained by CPLD. These films are featured by a high optical transmission (>95%), the lowest resistivity (8.6 × 10−4 Ωcm) being observed for an indium content of about 44–49 at.%. Organic heterostructures based on arylenevinylene oligomers (P78 and P13) or arylene polymers (AMC16 and AMC22) were obtained by MAPLE. In the case of ITO/P78/Alq3/Al heterostructures, a higher current value is obtained when the film thickness increases. Also, a photovoltaic effect was observed for heterostructures based on AMC16 or AMC22 deposited on ITO covered by a thin layer of PEDOT:PSS. Due to their optical and electrical properties, such organic heterostructures can be interesting for the organic photovoltaic cells (OPV) applications.
Part of the book: Nanoscaled Films and Layers
Metal Oxide Nanowires as Building Blocks for Optoelectronic Devices
Metal oxide nanowires have become the new building blocks for the next generation optoelectronic devices due to their specific features such as quantum confinement and high aspect ratio. Thus, they can be integrated as active components in diodes, field effect transistors, photodetectors, sensors, solar cells and so on. ZnO, a n-type semiconductor with a direct wide band gap (3.3 eV) and CuO, a p-type semiconductor with a narrow band gap (1.2–1.5 eV), are two metal oxides which were recently in the spotlight of the researchers for applications in the optoelectronic devices area. Therefore, in this chapter we focused on ZnO and CuO nanowires, the metal oxides nanowire arrays being prepared by straightforward wet and dry methods. Further, in order to emphasize their intrinsic transport properties, lithographic and thin films deposition techniques were used to integrate single ZnO and CuO nanowires into diodes and field effect transistors.
Part of the book: Nanowires
Pulsed Laser Deposition of Transparent Conductive Oxides on UV-NIL Patterned Substrates for Optoelectronic Applications
Transparent conductive oxide (TCO) electrodes are key components in the fabrication of optoelectronic devices such as organic photovoltaic cells (OPVs) or organic emitting devices (OLEDs). Pulsed laser deposition (PLD) results in TCO coatings with adequate optical and electrical properties, the preservation of the target chemical composition in the transferred films being the major advantage of this technique. Furthermore, the performance of the optoelectronic devices can be enhanced by patterning the TCO electrodes. Indium tin oxide (ITO) remains the most popular TCO due to its high conductivity and transparency. The scarcity of the indium resources encouraged the efforts to find an alternative to ITO, a promising candidate being Al-doped ZnO (AZO). Therefore, this chapter is focused on PLD deposition of TCO films (ITO and AZO) on patterned glass substrates prepared by ultraviolet nanoimprint lithography (UV-NIL) for obtaining transparent electrodes with improved characteristics, which further can be integrated in optoelectronic applications.
Part of the book: Thin Films