School of Chemistry - Research Publications
Now showing items 1-12 of 410
Gas-assisted preparation of lead iodide perovskite films consisting of a monolayer of single crystalline grains for high efficiency planar solar cells
(ELSEVIER SCIENCE BV, 2014-11-01)
The simple planar configuration of organic-inorganic hybrid perovskite solar cells produced by a solution coating process has great potential to be a low-cost and high efficiency photovoltaic technology. However planar perovskite films produced by "normal" spin coating usually show a dendritic grain morphology giving many gaps in the film, resulting in poor coverage of the substrate and thus a low power conversion efficiency. Here a facile gas-assisted solution processing technique is reported that has changed the kinetics of nucleation and crystal growth of the perovskite during the spin coating, producing very uniform perovskite thin films consisting of densely packed single crystalline grains. This microstructure is an ideal candidate for the p-i-n solar cell device. Planar perovskite solar cells constructed from these films produced a highly reproducible average power conversion efficiency of 15.7 +/- 0.7%. The highest efficiency achieved was 17.0% with a slightly lower steady-state value of 16.5% at the maximum power output of the solar cell. Crown Copyright
The use of a polymer inclusion membrane as a sorbent for online preconcentration in the flow injection determination of thiocyanate impurity in ammonium sulfate fertilizer
(ELSEVIER SCIENCE BV, 2014-11-01)
A polymer inclusion membrane (PIM) is used for the first time as a sorbent in the construction of a preconcentration column to enhance the sensitivity in flow injection analysis (FIA). The PIM-coated column is readily prepared by coating the PIM containing poly(vinyl chloride), Aliquat 336, and 1-tetradecanol onto glass beads packed in a glass tube. The determination of trace amounts of thiocyanate in ammonium sulfate fertilizer demonstrates the potential of the proposed PIM-coated column in FIA. Thiocyanate standards or samples of relatively large volume (e.g. up to 20004) are injected into a nitrate carrier stream. The sample zone passes through the proposed preconcentration column where thiocyanate is concentrated in a smaller volume of a carrier solution thus resulting in up to 7.4 fold increase in sensitivity. Thiocyanate is detected spectrophotometrically after its reaction with Fe(III) downstream of the preconcentration column. The limits of detection of thiocyanate in the absence and presence of 20 g L-1 ammonium sulfate (S/N=2) are 0.014 and 0.024 mg L-1, respectively. Thiocyanate was successfully determined in several samples of ammonium sulfate fertilizer.
Toward Large Scale Roll-to-Roll Production of Fully Printed Perovskite Solar Cells
(Wiley-VCH Verlag, 2015)
Fully printed perovskite solar cells are demonstrated with slot-die coating, a scalable printing method. A sequential slot-die coating process is developed to produce efficient perovskite solar cells and to be used in a large-scale roll-to-roll printing process. All layers excluding the electrodes are printed and devices demonstrate up to 11.96% power conversion efficiency. It is also demonstrated that the new process can be used in roll-to-roll production.
Influence of moisture out-gassing from encapsulant materials on the lifetime of organic solar cells
(ELSEVIER SCIENCE BV, 2015-01-01)
The results of a study on the effects of encapsulant pre-conditioning (drying) on the durability of "conventional" and "inverted" bulk-heterojunction organic solar cells based on P3HT:PCBM are presented. The architectures of the conventional and inverted devices were ITO/PEDOT:PSS/P3HT: PCBM/Al and ITO/ZnO/P3HT:PCBM/MoO3/Ag, respectively. Quantitative analysis of the moisture content, moisture out-gassing, and re-absorbing properties of flexible barrier encapsulant films under ambient conditions was conducted. The effect of moisture out-gassing from the encapsulation materials on device performance was studied and the lifetime of conventional and inverted devices was found to decline significantly for the devices encapsulated using materials without pre-conditioning. This study reveals the essential role of pre-conditioning of materials in the encapsulation of organic photovoltaic devices. Current-voltage characteristics exhibit a clear increase in the series resistance of the devices during storage under ambient conditions, and Spectroscopic Impedance analysis indicates that charge-transport resistance within the devices increases significantly during the degradation process. The results are consistent with the primary degradation mechanism being corrosion at the metal-electrode surface.