Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 6, Issue 17, Pages 15061-15067Publisher
AMER CHEMICAL SOC
DOI: 10.1021/am503138d
Keywords
quantum dot; solar cell; redox mediator; charge transfer-induced spin crossover; maganese
Funding
- Institute for Critical Technology and Applied Science
- Oak Ridge Associated Universities
- Chemistry Department at Virginia Tech
- College of Science at Virginia Tech
Ask authors/readers for more resources
The advancement of quantum dot sensitized solar cell (QDSSC) technology depends on optimizing directional charge transfer between light absorbing quantum dots, TiO2, and a redox mediator. The nature of the redox mediator plays a pivotal role in determining the photocurrent and photovoltage from the solar cell. Kinetically, reduction of oxidized quantum dots by the redox mediator should be rapid and faster than the back electron transfer between TiO2 and oxidized quantum dots to maintain photocurrent. Thermodynamically, the reduction potential of the redox mediator should be sufficiently positive to provide high photovoltages. To satisfy both criteria and enhance power conversion efficiencies, we introduced charge transfer spin-crossover Mn-II/III complexes as promising redox mediator alternatives in QDSSCs. High photovoltages similar to 1 V were achieved by a series of Mn poly(pyrazolyl)borates, with reduction potentials similar to 0.51 V vs Ag/AgCl. Back electron transfer (recombination) rates were slower than Co(bpy)(3), where bpy = 2,2'-bipyridine, evidenced by electron lifetimes up to 4 orders of magnitude longer. This is indicative of a large barrier to electron transport imposed by spin-crossover in these complexes. Low solubility prevented the redox mediators from sustaining high photocurrent due to mass transport limits. However, with high fill factors (similar to 0.6) and photovoltages, they demonstrate competitive efficiencies with Co(bpy)(3) redox mediator at the same concentration. More positive reduction potentials and slower recombination rates compared to current redox mediators establish the viability of Mn poly(pyrazolyl)borates as promising redox mediators. By capitalizing on these characteristics, efficient Mn-II/III-based QDSSCs can be achieved with more soluble Mn-complexes.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available