Abstract
Organic Solar cells offer a promising route towards low-cost renewable energy production; however large-area production techniques and material deposition methods still represent a significant scientific and engineering challenge (1).The characteristics and functionality of polymeric semiconductor photovoltaic heterojunctions where examined. Based on blends of polyfluorenes (F8TBT), polythiophenes (P3HT) and fullerenes (PCBM), using spray-coating deposition techniques suitable for large areas (2) (3). This can be achieved using blends of o-dichlorobenzene and Chlorobenzene as the solvent medium. Thermal / solvent – vapour post annealing of films were also studied.
Using a multi-faceted characterisation approach, studying photoluminescence quenching, optical microscopy, the morphological properties of these blend films are studied in detail by AFM methods, showing favourable results, in terms of layer thickness and uniformity, and micron-scale properties of these blends morphology. An optimal concentration for spray coating polymers was found to be 5mg ml-1 of compound to solvent; with the compound being a 1:1 ratio of donor and acceptor polymers and the solvent being a 5:1 ratio of dichlorobenzene to chlorobenzene. This produced consistent thin films on the substrate for all combinations of polymers tested.
Thermal and solvent annealing was found to increase the photoluminescence quenching efficiency of the blends by 10% on average, aside from the F8TBT-PCBM blend, which did not seem to be affected by the either annealing process. Thermal and solvent annealing was also found to affect the morphology of the samples the roughness of the samples. Thermal annealing was found to decrease the roughness of the samples the most, with on average a decrease of 31.12%. Solvent annealing was found to decrease the roughness of the sample very little on average 6.23%, and in the case of F8TBT-PCBM, actually increased the roughness of the sample
| Date of Award | 2016 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Chris Finlayson (Supervisor) |