The Influence of Poly(3-Hexylthiophene) Regioregularity on Fullerene-Composite Solar Cell Performance
A comparison of three samples of poly(3-hexylthiophene) having regioregularities of 86, 90, and 96% is used to elucidate the effect of regioregularity on polymer-fullerene-composite solar cell performance. It is observed that polymer samples with lower regioregularity are capable of generating fullerene composites that exhibit superior thermal stability. The enhanced thermal stability of the composites is attributed to a lower driving force for polymer crystallization in the less regioregular polymer samples, which is supported with two-dimensional grazing incidence X-ray scattering and differential scanning calorimetry measurements. Furthermore, it is demonstrated that all three polymer samples are capable of generating solar cells with equivalent peak efficiencies of {approx}4% in blends with [6,6]-phenyl-C{sub 61}-butyric acid methyl ester. While it may be non-intuitive that polymers with lower regioregularity can exhibit higher efficiencies, it is observed that the charge-carrier mobility of the three polymers is on the same order of magnitude (10{sup -4} cm{sup 2} V{sup -1} s{sup 01}) when measured from the space-charge-limited current, suggesting that highly regioregular and crystalline polythiophenes are not required in order to effectively transport charges in polymer solar cells. Overall, these results suggest a design principle for semicrystalline conjugated polymers in fullerene-composite solar cells in which crystallization-driven phase separation can be dramatically suppressed via the introduction of a controlled amount of disorder into the polymer backbone.
- Research Organization:
- Stanford Linear Accelerator Center (SLAC)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 953509
- Report Number(s):
- SLAC-REPRINT-2009-374
- Journal Information:
- J. Am. Chem. Soc 130:16324,2008, Journal Name: J. Am. Chem. Soc 130:16324,2008 Journal Issue: 48 Vol. 130; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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