3 research outputs found
Aerosol processing of halide perovskites
No full textOrgano-metal halide perovskites (OMHPs) research has progressed rapidly, with photovoltaic (PV) devices reaching over 20% efficiency. However, scalable production of these devices is an ongoing challenge. This study demonstrated the ability to grow halide perovskite films via aerosol assisted chemical vapour deposition (AACVD). AACVD is a scalable deposition process and one advantage of this method compared to conventional CVD is the fact that the precursors do not need to be vapourised. This allows for lower operating temperature, less complex equipment, and therefore lower overall cost.
In this thesis, Methylammonium lead-triiodide (MAPI) films were deposited by sequentially passing aerosolized precursor solvent solutions into a reactor containing a heated substrate. In this study two different precursor systems were utilized, one based on lead iodide and the other on lead acetate. The first produced thick films, which were characterized extensively using X-ray diffraction, UV-visible spectroscopy, Kelvin probe measurements, ambient photoemission spectroscopy, time of flight measurements and Hall effect measurements. The second system allowed for the deposition of thinner films, more suitable for photovoltaic applications. These films were again extensively characterised but also allowed for the fabrication of the first working OMHP device utilising AACVD.
Furthermore, this study demonstrated an ability to use aerosols as a scalable post-deposition treatment on existing films, modulating the morphology and boosting the performance of conventionally spin-coated films to over 20% PCE. Treatment of films was accomplished by exposing spin-coated films to aerosolised solvents. Using these treatments, it is shown that the morphology of the films can be drastically and controllably improved. This study also reveals improvements in charge carrier lifetimes and a general improvement in most (PV) parameters. This has further led to experimentation with HTL-free devices and thick OMHP layers, with both showing significant improvements after the aerosol treatment.Open Acces
Hybrid Solar Cells
No full textThe field of hybrid solar cells promises a combination of the economic and easy production of organic molecules, with the stability and performance of inorganic materials. One of the pioneering developments in this field was the creation of the dye-sensitized solar cell in 1991. A number of different organic and inorganic material combinations have since been researched. Device architecture has also been extensively explored, with many variations in how the organic and inorganic layers are arranged and deposited. Inorganic layers have attracted much attention. Likewise, research into electrolytes has shown great advances, with some of the latest research showing positive results with solid state electrolytes. The sensitizer or dye has also been an area of intense research. To date, many different organic dye families have been explored in an effort to improve efficiency. Methylammonium lead triiodide perovskite is one of the more recent dyes and showed an incredible increase in efficiency. This ushered in a new field of research based on perovskite-type sensitizers. There is currently a drive to produce more stable and higher performing perovskites. Variations in composition and stoichiometry have so far yielded a large number of improvements, but stability is still a major concern. Both of these hybrid cell technologies are very promising. However, this field is still immature, with much development still required to improve stability and processing.</jats:p
Intrinsic properties of Hellenic “Marls”
No full textPost-alpine deposits cover substantial areas of Hellas. The fine grained facies of these deposits, comprise a wide range of over consolidated materials of varying grading and mineralogy. On average, however, these deposits cover different depositional environments and may be classed as silty clays and clayey silts of low to intermediate plasticity containing calcite in their mineralogical suite. Such deposits have been collectively known to practising engineers as marls. A concerted effort to collect field and laboratory data and interpret the behaviour of these materials was recently launched in view of the involvement of the aforesaid mentioned deposits in a series of geotechnical problems. This thesis aspires to contribute to this knowledge and provide a framework on which the field performance of such materials may be interpreted. To that end, disturbed and high quality undisturbed samples from the geologically dissimilar areas of Korinthos, Preveza-Igoumenitsa road axis and Amalias- Goumeron were obtained and tested in order to ascertain their physical characteristics and mineralogical composition. Further, engineering properties which are independent of stress history, i.e. intrinsic, of the materials sampled, were determined. These were the residual strength as determined by ring shearing and the compressibility of reconstituted samples. The performance of the samples was assessed in terms of grain size distribution and mineralogy. The results show that any attempt to explain or predict intrinsic properties of Hellenic fine grained calcareous sediments without taking simultaneous account of gradation and mineralogy is incomplete and therefore inaccurate
