1:30 PM - 3:30 PM
[20p-PB4-56] Modulation of Orbital Energy Levels of Tetrabenzoporphyrin toward Increased Open-Circuit Voltage and Possibility as n-Type Material in Organic Solar Cells
Keywords:organic semiconducting materials, organic photovoltaic cells, wet processes
Tetrabenzoporphyrin (BP) is an organic p-type molecular semiconductor having a large π-conjugated system which can form effective charge-carrier paths in the solid state. However, BP has a poor solubility in any solvents, making its processing by cost-effective solution-based techniques quite difficult. This problem has been evaded via a “thermal precursor approach” in which a soluble precursor 1,4:8,11:15,18:22,25-tetraethano-29H,31H-tetrabenzo[b,g,l,q]porphyrin (CP) is solution-deposited then thermally converted to BP by in situ retro-Diels-Alder reaction. By taking advantage of this approach, power conversion efficiencies (PCEs) of over 5% have been achieved with BP or its derivatives. However, the open-circuit voltage (VOC) in these devices is relatively low because of the high energy level of the highest occupied molecular orbital (HOMO) of BP.
In this work, a new derivative named 2CF3BP has been designed and evaluated as active-layer material in organic solar cells (OSCs). As 2CF3BP is poor in solubility, it is solution-deposited via the thermal precursor approach from its soluble precursor 2CF3CP. A lower HOMO level than that of BP is achieved owing to the strongly electron-withdrawing trifluoromethyl groups. Consequently, 2CF3BP based OSCs show high VOC values of up to 0.96 V, which is the highest obtained so far with BP or its derivative. In addition, the introduction of two trifluoromethyl groups effectively reduced the energy level of the lowest unoccupied molecular orbital (LUMO), allowing 2CF3BP to serve as n-type material in OSCs. The thin-film characteristics and device performance will be discussed in detail in the presentation.
In this work, a new derivative named 2CF3BP has been designed and evaluated as active-layer material in organic solar cells (OSCs). As 2CF3BP is poor in solubility, it is solution-deposited via the thermal precursor approach from its soluble precursor 2CF3CP. A lower HOMO level than that of BP is achieved owing to the strongly electron-withdrawing trifluoromethyl groups. Consequently, 2CF3BP based OSCs show high VOC values of up to 0.96 V, which is the highest obtained so far with BP or its derivative. In addition, the introduction of two trifluoromethyl groups effectively reduced the energy level of the lowest unoccupied molecular orbital (LUMO), allowing 2CF3BP to serve as n-type material in OSCs. The thin-film characteristics and device performance will be discussed in detail in the presentation.