Dr James Ball

Abstract:

Graphene-based electronics show much promise due to the potential high charge-carrier mobility of the material as well as its flexibility in preparation on different substrates. Recently there has been much evidence suggesting that the wrinkle structures found in pristine graphene inhibit electron transport, reducing device performance. In this study the inhibiting role of standing wrinkles within chemically derived graphene are studied quantitatively using Kelvin force microscopy. Samples were evaluated before and after annealing at 250 C to observe changes in the channel's surface potential dependence on the state of reduction. Annealed samples were found to have inter-flake and intra-flake contribution to the potential drop and that for the latter a correlation between the potential drop magnitude and wrinkle density is found, although there is no correlation with wrinkle height. Statistical averaging across many images demonstrated that the average lower limit of wrinkle resistance in these devices is approximately 4.5 kΩ. Such high resistance demonstrate definitively that elimination of wrinkles within graphene oxide based devices is essential in order to obtain optimum performance. © 2013 Elsevier Ltd. All rights reserved.

Abstract:

Organometal trihalide perovskite solar cells offer the promise of a low-cost easily manufacturable solar technology, compatible with large-scale low-temperature solution processing. Within 1 year of development, solar-to-electric power-conversion efficiencies have risen to over 15%, and further imminent improvements are expected. Here we show that this technology can be successfully made compatible with electron acceptor and donor materials generally used in organic photovoltaics. We demonstrate that a single thin film of the low-temperature solution-processed organometal trihalide perovskite absorber CH3NH3PbI3-xClx, sandwiched between organic contacts can exhibit devices with power-conversion efficiency of up to 10% on glass substrates and over 6% on flexible polymer substrates. This work represents an important step forward, as it removes most barriers to adoption of the perovskite technology by the organic photovoltaic community, and can thus utilize the extensive existing knowledge of hybrid interfaces for further device improvements and flexible processing platforms.

Abstract:

With contributions by experts in diverse fields of chemistry, physics, materials science, and medicine, this comprehensive survey of the current state of knowledge of nanotechnology highlights the great potentiality of the field.

Abstract:

The family of hollow ellipsoid fullerenes is an important and widely studied class of small molecule semiconducting materials used in various electronic devices. In this chapter, we will outline the electronic properties of fullerenes, their preparation in thin-films, and the physics of devices in which they are used. Furthermore, we will highlight important advances in the field of fullerene-based electronics and offer an outlook on future directions and challenges. © 2012 Pan Stanford Publishing Pte. Ltd. All rights reserved.