Novel Materials and Deposition Techniques for Solution Processed Solar Cells

Whilst many advances have been made in the field of solution processed solar cells (SPSCs), there is still much work to be done if they are to fulfil their potential and reduce the cost of commercial photovoltaic devices. This thesis aims to assist in moving towards this objective by investigating ways to overcome some of the barriers to the commercialization of SPSCs. Such barriers include the costly and mechanically brittle electrode material of indium tin oxide, the use of solution deposition techniques which are not compatible with large-scale production, and a lack of understanding of the properties of promising new semiconducting materials such as organometal halide perovskites. In this work a novel indium-free multilayer semi-transparent electrode has been fabricated and incorporated as the anode in polymer solar cells. Whilst molybdenum oxide is typically used as the ‘seed layer’ material in such trilayer structures, its replacement with tellurium dioxide has been found to lead to an enhanced transmittance in the optimised electrodes and to an increased short circuit current when such electrodes are employed in polymer solar cells. The roll-to-roll compatible deposition technique of ultrasonic spray-coating has, for the first time, been successfully used for the fabrication of films of the organometal trihalide perovskite CH3NH3PbI3-xClx. Such films were subsequently successfully employed as the active layer in planar solar cells. This deposition technique is then extended to hole transporting and electron transporting materials in order to move towards a fully spray-deposited solar cell. Finally, a combination of structural investigation techniques have been employed to monitor the formation of the perovskite CH3NH3PbI3-xClx during thermal annealing of a precursor film. In-situ X-ray scattering measurements are used together with ex-situ scanning electron microscopy in order to correlate the evolution of the film during annealing to solar cell performance. In addition, the activation energy for the transition from precursor to perovskite has been calculated

Towards Oxide Electronics:a Roadmap

At the end of a rush lasting over half a century, in which CMOS technology has been experiencing a constant and breathtaking increase of device speed and density, Moore's law is approaching the insurmountable barrier given by the ultimate atomic nature of matter. A major challenge for 21st century scientists is finding novel strategies, concepts and materials for replacing silicon-based CMOS semiconductor technologies and guaranteeing a continued and steady technological progress in next decades. Among the materials classes candidate to contribute to this momentous challenge, oxide films and heterostructures are a particularly appealing hunting ground. The vastity, intended in pure chemical terms, of this class of compounds, the complexity of their correlated behaviour, and the wealth of functional properties they display, has already made these systems the subject of choice, worldwide, of a strongly networked, dynamic and interdisciplinary research community. Oxide science and technology has been the target of a wide four-year project, named Towards Oxide-Based Electronics (TO-BE), that has been recently running in Europe and has involved as participants several hundred scientists from 29 EU countries. In this review and perspective paper, published as a final deliverable of the TO-BE Action, the opportunities of oxides as future electronic materials for Information and Communication Technologies ICT and Energy are discussed. The paper is organized as a set of contributions, all selected and ordered as individual building blocks of a wider general scheme. After a brief preface by the editors and an introductory contribution, two sections follow. The first is mainly devoted to providing a perspective on the latest theoretical and experimental methods that are employed to investigate oxides and to produce oxide-based films, heterostructures and devices. In the second, all contributions are dedicated to different specific fields of applications of oxide thin films and heterostructures, in sectors as data storage and computing, optics and plasmonics, magnonics, energy conversion and harvesting, and power electronics