Nanoporous anodic alumina (AAO) templates are routinely created with ease on substrates, particularly Si wafers. However, the inability to stabilize Al anodization on indium tin oxide (ITO) glass is a key stumbling block that has prevented AAO-assisted deposition of nanomaterial arrays extending from ITO that are attractive for a range of opto-electronic applications (e.g., solar cells and photonic devices). We report on the processing of stable AAO templates directly on ITO substrates by utilizing an ultrathin (0.3 nm) adhesion/passivation layer of Ti between ITO and Al. Precise control of the Ti layer thickness to within the subnanometer (0.2-0.5 nm) range is essential for the anodization process for two factors: (1) to prevent the delamination of Al and destruction of ITO; and (2) to prevent the formation of thick barrier layers at the bottom of the pore channels, which prevent pore connectivity to the conductive ITO substrate. We explore the complex correlation between the electrical properties of substrates (and interlayers) and barrier layer formation and further highlight the criteria for successful barrier layer removal.
Dense and well‐aligned arrays of TiO2 nanotubes extending from various substrates are successfully fabricated via a new liquid‐phase atomic layer deposition (LALD) in nanoporous anodic alumina (AAO) templates followed by alumina dissolution. The facile and versatile process circumvents the need for vacuum conditions critical in traditional gas‐phase ALD and yet confers ALD‐like deposition rates of 1.6–2.2 Å cycle−1, rendering smooth conformal nanotube walls that surpass those achievable by sol–gel and Ti‐anodizing techniques. The nanotube dimensions can be tuned, with most robust structures being 150–400 nm tall, 60–70 nm in diameter with 5–20 nm thick walls. The viability of TiO2 nanotube arrays deposited on indium tin oxide (ITO)–glass electrodes for application in model hybrid poly(3‐hexylthiophene) (P3HT):TiO2 solar cells is studied. The results achieved provide platforms and research directions for further advancements.
Furan substituted diketopyrrolopyrrole (DBF) combined with benzothiadiazole based polymer semiconductor PDPP-FBF has been synthesized and evaluated as an ambipolar semiconductor in organic thin-film transistors. Hole and electron mobilities as high as 0.20 cm(2) V(-1) s(-1) and 0.56 cm(2) V(-1) s(-1), respectively, are achieved for PDPP-FBF.
In this paper, we have synthesized two novel diketopyrrolopyrrole (DPP) based donor–acceptor (D–A) copolymers poly{3,6-dithiophene-2-yl-2,5-di(2-octyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-1,5-bis(dodecyloxy)naphthalene} (PDPPT-NAP) and poly{3,6-dithiophene-2-yl-2,5-di(2-butyldecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-2-dodecyl-2H-benzo[d][1,2,3]triazole} (PDPPT-BTRZ) via direct arylation organometallic coupling. Both copolymers contain a common electron withdrawing DPP building block which is combined with electron donating alkoxy naphthalene and electron withdrawing alkyl-triazole comonomers. The number average molecular weight (M(n)) determined by gel permeation chromatography (GPC) for polymer PDPPT-NAP is around 23400 g mol(−1) whereas for polymer PDPPT-BTRZ it is 18600 g mol(−1). The solid state absorption spectra of these copolymers show a wide range of absorption from 400 nm to 1000 nm with optical band gaps calculated from absorption cut off values in the range of 1.45–1.30 eV. The HOMO values determined for PDPPT-NAP and PDPPT-BTRZ copolymers from photoelectron spectroscopy in air (PESA) data are 5.15 eV and 5.25 eV respectively. These polymers exhibit promising p-channel and ambipolar behaviour when used as an active layer in organic thin-film transistor (OTFT) devices. The highest hole mobility measured for polymer PDPPT-NAP is around 0.0046 cm(2) V(−1) s(−1) whereas the best ambipolar performance was calculated for PDPPT-BTRZ with a hole and electron mobility of 0.01 cm(2) V(−1) s(−1) and 0.006 cm(2) V(−1) s(−1) .
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