Synthesis and Applications of Benzothiadiazole and Carbazole-Containing Molecules for Organic Solar Cell
Date Issued
2009
Date
2009
Author(s)
Chiang, Shang-Te
Abstract
In this study, the carbazole derivatives with benzothiadiazole-containing donor-acceptor structure for organic solar cell have been successfully synthesized via Suzuki and Ullmann coupling. Carbazole-, thiophene- and methoxybenzene-containing conjugated group have been introduced into compound O1, O2 and O3. In thermogravimetry analysis, O1, O2, O3 were found with good thermal stability and 5% thermal degradation temperature over 300 oC. The glass transition temperature of O1 was observed and characterized by a differential scanning calorimetery at 85.2 oC, but no melting point was found due to its twisted structure. Melting point of O2 and O3 can be found at 63.6 and 128.7 oC. In cyclic voltammetry, the oxidation potential of O1 is higher than O2 and O3 due to its lower electron density. The HOMO of compounds was estimated at -5.31~-5.44 eV. The absorption spectra of above-mentioned compounds were found to be a two-peak diagram which can be attributed to their donor-acceptor structure. The shifting of short-wavelength absorption peak was observed in UV-Vis spectrum with changing different conjugated groups (λAbs = 321nm, 323nm, 309nm for O1, O2, O3 respectively). The long-wavelength absorption peak was found to be located at the same wavelength (λAbs = 450 nm) for 3 compounds for the same donor-acceptor structure. And the energy gap of compounds was found to be the same (2.3 eV) and their LUMO was estimated at -3.01~-3.14 eV. From all the properties analysis, O1, O2 and O3 are found to be the promising material for their applications in the bulk heterojunction organic solar cell. The preliminary bulk heterojunction solar cell devices were fabricated with compound O1. The best device with O1:PCBM = 1:2 shows power conversion efficiencies 0.013% with open-circuit voltage(VOC) of 0.65V, short-circuit current density (JSC) of 0.067 mA/cm2 and fill factor(FF) 29.2 % under AM1.5G solar simulator.
Subjects
carbazole
benzothiadiazole
bulk heterojunction
organic solar cell
Type
thesis
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