1:30 PM - 1:45 PM
[12p-N322-2] [Highlight]Realizing a High Fill Factor of 0.8 in Organic Solar Cells with Thick Active Layers
Keywords:semiconducting polymer, organic solar cells, fill factor
An increase of the photoactive layer thickness in an organic solar cell is essential to improve photocurrent and hence the power conversion efficiency. However, thickening the photoactive layer always brings about a significant decrease in the fill factor due to the low charge carrier mobility of the organic semiconductor. Thus, to overcome the trade-off between thick film and fill factor, it is important to develop organic semiconductors with high charge carrier mobility in particular through the film thickness.
Here, we show that a new polymer based on dithienonaphthobisthiadiazole (TNT) demonstrated significantly high fill factors of around 0.8 with thick films of close to 300 nm in fullerene-based cells, which are among the highest values for thick organic solar cells. Further, the maximum power conversion efficiency of close to 12% was observed at a thickness of more than 400 nm. The polymer/fullerene blend film showed high hole mobilities in the order of 10–2 cm2/Vs based on the space-charge limited current model, which accounted for the suppressed bimolecular recombination. The high hole mobility likely originated in the extremely large π–π overlap between the TNT moieties in the π-stacked polymer chains, as suggested by the crystal structure of the model compound. We will also discuss the structure-property relationship of TNT-based polymer in comparison with its counterpart, naphthobisthiadiazole (NTz)-based polymer.
Here, we show that a new polymer based on dithienonaphthobisthiadiazole (TNT) demonstrated significantly high fill factors of around 0.8 with thick films of close to 300 nm in fullerene-based cells, which are among the highest values for thick organic solar cells. Further, the maximum power conversion efficiency of close to 12% was observed at a thickness of more than 400 nm. The polymer/fullerene blend film showed high hole mobilities in the order of 10–2 cm2/Vs based on the space-charge limited current model, which accounted for the suppressed bimolecular recombination. The high hole mobility likely originated in the extremely large π–π overlap between the TNT moieties in the π-stacked polymer chains, as suggested by the crystal structure of the model compound. We will also discuss the structure-property relationship of TNT-based polymer in comparison with its counterpart, naphthobisthiadiazole (NTz)-based polymer.