Finding renewable sources of energy is becoming an increasingly important component of scientific research. Greater competition for existing sources of energy has strained the world’s supply and demand balance and has increased the prices of traditional sources of energy such as oil, coal, and natural gas. The experiment discussed in this paper is designed to identify and build an inexpensive and simple method for creating an effective organic solar cell.

No description available.

With the global energy demand projected to grow rapidly, it is imperative to divest from traditional greenhouse gas-based power production toward renewable energy sources such as solar. In recent years, solar photovoltaics (PV) hold a large share among renewables sources. Currently, the market is dominated by crystalline silicon solar cells due to their low levelized cost of energy (LCOE) values. However, to sustain this progress, the power conversion efficiency of PV devices must be further improved since tiny costs cut from the other expenses is difficult. On the other hand, the margin for the PCE improvement in c-Si technology is also quite limited since the technology is approaching its practical limits. At this stage, coupling c-Si devices with another efficient solar cell in tandem configuration is a promising way to overcome this challenge. Perovskite solar cells (PSCs) represent a breakthrough solar technology to enable this target due to their proven high efficiency and potential cost-effectiveness. Whereas perovskite/silicon tandem solar cells are promising, their operational stabilities are still a significant concern for market entry. Here, the degradation mechanism of n-i-p perovskite/Si tandem solar cells was investigated. Thermal stability tests have shown severe degradation in such tandem devices. On the other hand, tandem devices were relatively stable when placed in a humidity cabinet with 25% relative humidity (RH). Conversely, temperature degraded devices showed cracks all over the perovskite surface and rupture in the top electrode after 1000 hrs at 85 oC. Additionally, silver iodide formation was depicted in XRD and XPS analysis. To enhance the stability, methods to reduce the hysteresis were studied. First, potassium chloride (KCl) was applied as a passivation agent to the electron transport layer (ETL) to reduce surface defects. Second, 2D passivation was applied to reduce trap density and enhance the crystallinity of the perovskite film. Finally, organic molecules were placed between the hole transport layer (HTL) and metal-oxide interface as interlayers to prevent diffusion of metal oxide to the HTL and accumulation of the dopant at the metal-oxide interface. After passivation and interface layers, stability enhanced but further improvement is still required.

Finding renewable sources of energy is becoming an increasingly important component of scientific research. Greater competition for existing sources of energy has strained the world’s supply and demand balance and has increased the prices of traditional sources of energy such as oil, coal, and natural gas. The experiment discussed in this paper is designed to identify and build an inexpensive and simple method for creating an effective organic solar cell.

Finding renewable sources of energy is becoming an increasingly important component of scientific research. Greater competition for existing sources of energy has strained the world’s supply and demand balance and has increased the prices of traditional sources of energy such as oil, coal, and natural gas. The experiment discussed in this paper is designed to identify and build an inexpensive and simple method for creating an effective organic solar cell.

No description available.

The semiconducting sulphosalt Wittichenite has been identified as a possible absorber material for thin film photovoltaic devices. It has the chemical formula Cu3BiS3 and its component elements are those of low toxicity and high abundance making it a very attractive prospect for photovoltaic devices. The copper bismuth sulphur material system is not very well understood and information on it limited to a few small regions. To aid understanding of this system a pseudo-binary phase diagram along the CuS-Bi join of the Cu-Bi-S ternary phase diagram was constructed by making bulk samples of various compositions along the join and analysing them using X-ray diffraction and differential scanning calorimetry. This join was chosen because is crosses the point at which Cu3BiS3 would be expected to occur due to its stoichiometry. The CuS-Bi phase diagram shows Cu3BiS3 forms across a wide compositional range but is mixed with either bismuth metal or copper sulphides depending on composition. Films of Cu3BiS3 were made using sputtered copper and bismuth films annealed in a sulphur atmosphere and thermal co- evaporation of copper sulphide and bismuth.

In the global context of increasing oil prices and public concern regarding the safety of nuclear plants, renewable forms of energy are called upon to play a major role in tomorrow’s energy market. Among the various forms of renewable energies, solar power holds the greatest potential for development. Despite the constant improvement of photovoltaic technologies over the past few year, these technologies are rapidly approaching the theoretic performance limits. New ideas and materials are required to overcome this bottleneck and to take full advantage of solar power. With a band-gap energy spanning the full solar spectrum, and an absorption coefficient ten times higher than competing materials, indium gallium nitride alloys are amongst the most promising solar-cell materials. Nevertheless, fundamental issues related to the fabrication and doping of InGaN alloys still hamper the development of InGaN-based photovoltaics. In the present thesis, conducted within the framework of the ANR project NewPVonGlass, the growth of InGaN alloys suitable for photovoltaics using metalorganic vapor-phase epi- taxy (MOVPE) is studied. A combination of several cutting-edge characterization tools is employed to determine the fundamental mechanism that govern the growth of InGaN. Based on the results of this study, an innovative procedure that allows the growth of hig-quality InGaN epitaxial layers is demonstrated and is used for the fabrication of InGaN-based solar cells.

Octahedral, six co-ordinate ruthenium complexes containing acid substituted polypyridyl ligands have proved particularly successful as dyes for Dye-Sensitised Solar Cells (DSSCs); thus there have been hundreds, if not thousands of these types of complexes synthesised and studied. Ruthenium dyes are now incorporated into commercial DSSCs; yet there is limited understanding of the interactions between the dye and the liquid I-/I3- electrolyte, which can both facilitate and hinder the generation of current and voltage within the cell. Monodentate –NCS ligands incorporated into ruthenium dyes appear to interact strongly with I- and I2 within the electrolyte. The analogous –NCO containing dye has therefore been synthesised to study the effect of the chalcogen atom on these interactions. Substituting –NCS for -NCO resulted in a significant change in the spectroscopic and electronic properties of the molecular dye, with destabilisation of the HOMO of the dye causing a red shift in dye absorption. Possibly due to this change in properties, the nature of the chalcogen atom was shown to have a significant impact on the performance of the dye in a DSSC. The effect of the nature of substituents on ancillary ligands of Ru(H2-dcbpy)(4,4`-Y2- bpy)(NCS)2 dyes on recombination across the TiO2 – electrolyte interface within the cell has been proven significant due to changes in the strength of binding of I2 to the substituent groups. However, few substituent groups have been investigated; therefore a series of halogenated dyes, where Y = Cl, Br, were synthesised. The effect of the nature of the halogen on dye recombination was significant, although the trends observed were not consistent with the reported data for iodine binding. Similar trends were observed for the analogous series, Ru(H2-dcbpy)(5,5’-Y2- bpy)(NCS)2 where Y = F, Cl, Br. By comparison of this series of dyes with the 4,4` dyes, it was discovered that the position of the substituent had a significant effect on the rate of recombination within the solar cell, as well as the electrochemical and spectroscopic properties of the dyes themselves. Such isomeric effects have not been previously reported. In the synthesis of these dyes, and in attempting the synthesis of five other ruthenium dyes, many barriers to efficient dye synthesis were discovered. Therefore, an investigation into the synthesis of ruthenium dyes has been conducted. By analysis of the breakdown products formed a number of avoidable side reactions, including decarboxylation and ruthenium catalysed nucleophilic substitution of the bpy ligands, were shown to occur. Problems associated with the high lability of the ruthenium centre at high temperatures have also been explored, and the use of UV/vis monitoring to aid optimisation of the reaction conditions was implemented. Thus, the development of two novel synthetic procedures allowed the synthesis of the dyes investigated during the course of this thesis.

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy