Photoelectrochemical cells based on inherently conducting polymers

This review of photoelectrochemical cells (PECs) based on inherently conducting polymers (ICPs) deals with the mechanisms of operation and the various factors that influence the overall efficiency of PECs. The factors addressed include ICP composition and oxidation state, the use of nanostructured surfaces and interfaces, and the PEC electrolyte and redox mediator

Driving Course Engagement Through Multimodal Strategic Technologies

This paper describes the development of a new second-year level undergraduate Physics course at the University of Newcastle, comprising three four-week modules (encompassing Special Relativity, Nuclear and Particle Physics) for a combined roster of both Newcastle and James Cook students. A series of multimodal digital learning technology platforms were employed to see if they could maximise student engagement. Specifically, a flipped classroom system was trialled whereby students were tasked with creating their own lecture notes from online videos (created using Lightboard and PowerPoint). This approach resulted in 90% of the class actively engaging with the lecture content. Weekly online tutorial workshops consistently achieved an attendance rate of approximately 85% and included an online quiz based on embedded questions within the lecture videos. In addition, innovative STEM laboratory workshops exploited active engagement strategies including purely online worksheets to blended and remote experiments. The inclusion of a Slack-based project management hub enabled students to work seamlessly under constantly changing COVID-19 restrictions while exposing them to planning, management and Python control coding, under the visage of “embracing technology and best practice to deliver the greatest possible student experience”. A review of students’ view of the Lightboard and PowerPoint lecture content was conducted with Lightboard being the student’s outright preference

Image formation in the scanning helium microscope

The scanning helium microscope (SHeM) is a new addition to the array of available microscopies, particularly for delicate materials that may suffer damage under techniques utilising light or charged particles. As with all other microscopies, the specifics of image formation within the instrument are required to gain a full understanding of the produced micrographs. We present work detailing the basics of the subject for the SHeM, including the specific nature of the projection distortions that arise due to the scattering geometry. Extension of these concepts allowed for an iterative ray tracing Monte Carlo model replicating diffuse scattering from a sample surface to be constructed. Comparisons between experimental data and simulations yielded a minimum resolvable step height of (67 ± 5) µm and a minimum resolvable planar angle of (4.3 ± 0.3)° for the instrument in question.acceptedVersio

Utilizing energy transfer in binary and ternary bulk heterojunction organic solar cells

Energy transfer has been identified as an important process in ternary organic solar cells. Here, we develop kinetic Monte Carlo (KMC) models to assess the impact of energy transfer in ternary and binary bulk heterojunction systems. We used fluorescence and absorption spectroscopy to determine the energy disorder and Förster radii for poly(3-hexylthiophene-2,5-diyl), [6,6]-phenyl-C61-butyric acid methyl ester, 4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine (DIBSq), and poly(2,5-thiophene-<i>alt</i>-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3′,2′-<i>h</i>][1,5]naphthyridine-5,10-dione). Heterogeneous energy transfer is found to be crucial in the exciton dissociation process of both binary and ternary organic semiconductor systems. Circumstances favoring energy transfer across interfaces allow relaxation of the electronic energy level requirements, meaning that a cascade structure is not required for efficient ternary organic solar cells. We explain how energy transfer can be exploited to eliminate additional energy losses in ternary bulk heterojunction solar cells, thus increasing their open-circuit voltage without loss in short-circuit current. In particular, we show that it is important that the DIBSq is located at the electron donor–acceptor interface; otherwise charge carriers will be trapped in the DIBSq domain or excitons in the DIBSq domains will not be able to dissociate efficiently at an interface. KMC modeling shows that only small amounts of DIBSq (<5% by weight) are needed to achieve substantial performance improvements due to long-range energy transfer

Measurement of molecular order and orientation in nanoscale organic films

Self-assembled monolayers (SAMs) have, in recent years, attracted much interest for surface modification, surface coatings and as interfacial coupling agents. X-ray photoelectron spectroscopy (XPS) and carbon K-edge near edge X-ray absorption fine structure (NEXAFS) have been used to non-destructively measure the molecular conformation of organic films with thickness of the order of 1nm. Three different types of molecular conformation were found for &#x03b3;-aminopropyltriethoxysilane (&#x03b3;-APS) films formed on ZnO surfaces. The orientation of &#x03b3;-APS films was observed to vary with adsorption time and surface coverage. Thus the molecular conformation of thin films can be controlled through adjustment of the application parameters

Photoenhanced injection currents in organic solar cells

Bulk heterojunction organic solar cells with the general structure: indium tin oxide/polyethylenethioxythiophene (PEDOT)/bulk-heterojunction layer/Al with built-in fields between –0.1 and 1 V have been fabricated by electrochemically doping the PEDOT electrode. The active bulk-heterojunction layer consisted of a blend of MDMO-PPV (poly(2-methoxy-5-(3',7'-dimethyl)octyloxy-1,4-phenylenevinylene)) and PCBM ((6,6)-phenyl-C₆₁-butyric-acid methyl ester)). Measurements of the current–voltage curves with varying light intensities for these devices reveal the presence of light-dependent currents in addition to those from the photogenerated charge carriers. Equivalent circuit modeling indicates that these light-dependent currents most likely originate from photoenhanced injection at the electrodes

Poly(2,3-dihexylthieno[3,4-b]pyrazine) via GRIM polymerization: simple preparation of a solution processable, low-band-gap conjugated polymer (letter)

Conjugated polymers continue to attract attention due to their tunable optical and electronic properties, which has led to such applications as light-emitting diodes (LEDs), photovoltaic devices, and field effect transistors. Many desirable properties are dependent on the material’s band gap (Eg), which is the energy between the filled valence and empty conduction bands and thus corresponds to the HOMO-LUMO gap of the solid state material. The Eg therefore determines both the lowest energy absorbance of the material and the energy of any potential emission. Lower Eg values also result in enhanced thermal population of the conduction band, thus increasing the number of intrinsic charge carriers, and the lower oxidation potential associated with a low Eg can result in the stabilization of the corresponding doped (i.e., oxidized) state. High-purity pTPs can be easily produced via GRIM methods to give soluble materials with low polydispersities, enhanced processability, and reduced band gaps in comparison to the FeCl₃ polymerized materials. The application of these GRIM-polymerized pTPs to photonic devices has been successfully demonstrated with devices giving spectral response to below 1200 nm

Fabricating semi-conducting polymer photonic structures via near-field scanning optical lithography

Near-field scanning optical lithography (NSOL) is a relatively new technique for patterning delicate organic thin films. Here, it has been used to fabricate a thin film optical phase grating in the semi-conducting polymer poly(p-phenylene vinylene). Recent advances in the development of the NSOL technique have been exploited to demonstrate its capability for producing photonic structures with nanoscale features despite the presence of a relatively large (200 nm diameter) NSOM tip. In particular, an intricate polymer photonic structure was designed (with fine scale features of the order of 250 nm) and then fabricated using the NSOL technique. The optical properties of the ideal phase grating were modelled and compared to the diffraction pattern produced by the fabricated structure. Comparison of the ideal and measured patterns showed the technique to be quite capable of consistently creating intricate polymer structures. The methodology employed represents a further step toward the construction of novel photonic devices