S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Material Science and Engineering (재료공학부) Journal Papers (저널논문_재료공학부)
Small Molecules Based on Thieno[3,4-c]pyrrole-4,6-dione for High Open-Circuit Voltage (VOC) Organic Photovoltaics: Effect of Different Positions of Alkyl Substitution on Molecular Packing and Photovoltaic Performance
- Choi, Yoon Suk; Shin, Tae Joo; Jo, Won Ho
- Issue Date
- American Chemical Society
- ACS Applied Materials and Interfaces, Vol.6 No.2014, pp. 20035-20042
- 공학; thienopyrroledione; organic solar cells; small molecules; high VOC, alkyl chain position
- Two different thienopyrroledione (TPD)-based small molecules (SMs) with different alkyl substitution positions were synthesized, and their photovoltaic properties are measured and compared to examine the effect of the alkyl substitution position on their optical, electrochemical, and photovoltaic properties. The use of TPD as an electron-accepting unit in conjugated SMs effectively lowers the highest occupied molecular orbital (HOMO) energy levels of the conjugated SMs and leads to high open-circuit voltage (VOC). The two SMs with n-hexyl group substituted at different positions exhibit almost identical optical and electrochemical properties in the pristine state. However, the crystallographic and morphological characteristics of the two SMs are significantly different, because they are blended with PC71BM.The SM in which n-alkyl groups are substituted at the centralaccepting unit exhibits a power conversion efficiency (PCE) of 6.0% with VOC = 0.94 V, which is among the highest PCE valuesof TPD-based SM devices, whereas the SM with n-alkyl groups being substituted at the chain ends shows a moderate PCE valueof 3.1%.
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