Ultrafast energy transfer in biomimetic multistrand nanorings.
Journal of the American Chemical Society ACS Publications 136:23 (2014) 8217-8220
Abstract:
We report the synthesis of LH2-like supramolecular double- and triple-stranded complexes based upon porphyrin nanorings. Energy transfer from the antenna dimers to the π-conjugated nanoring occurs on a subpicosecond time scale, rivaling transfer rates in natural light-harvesting systems. The presence of a second nanoring acceptor doubles the transfer rate, providing strong evidence for multidirectional energy funneling. The behavior of these systems is particularly intriguing because the local nature of the interaction may allow energy transfer into states that are, for cyclic nanorings, symmetry-forbidden in the far field. These complexes are versatile synthetic models for natural light-harvesting systems.Charge-carrier dynamics in vapour-deposited films of the organolead halide perovskite CH3NH3PbI3-xClx
Energy and Environmental Science Royal Society of Chemistry 7:7 (2014) 2269-2275
Abstract:
We determine high charge-carrier mobilities ≥ 33 cm2 V−1 s−1 and bi-molecular recombination rates about five orders of magnitude below the prediction of Langevin's model for vapour-deposited CH3NH3PbI3−xClx using ultrafast THz spectroscopy. At charge-carrier densities below ∼1017 cm−3 intrinsic diffusion lengths are shown to approach 3 microns, limited by slow mono-molecular decay processes.Lead-free organic–inorganic tin halide perovskites for photovoltaic applications
Energy and Environmental Science Royal Society of Chemistry 7:9 (2014) 3061-3068
Abstract:
Already exhibiting solar to electrical power conversion efficiencies of over 17%, organic-inorganic lead halide perovskite solar cells are one of the most promising emerging contenders in the drive to provide a cheap and clean source of energy. One concern however, is the potential toxicology issue of lead, a key component in the archetypical material. The most likely substitute is tin, which like lead, is also a group 14 metal. While organic-inorganic tin halide perovskites have shown good semiconducting behaviour, the instability of tin in its 2+ oxidation state has thus far proved to be an overwhelming challenge. Here, we report the first completely lead-free, CH3NH 3SnI3 perovskite solar cell processed on a mesoporous TiO2 scaffold, reaching efficiencies of over 6% under 1 sun illumination. Remarkably, we achieve open circuit voltages over 0.88 V from a material which has a 1.23 eV band gap.High charge carrier mobilities and lifetimes in organolead trihalide perovskites
Advanced Materials 26:10 (2014) 1584-1589
Abstract:
Organolead trihalide perovskites are shown to exhibit the best of both worlds: charge-carrier mobilities around 10 cm2 V-1 s -1 and low bi-molecular charge-recombination constants. The ratio of the two is found to defy the Langevin limit of kinetic charge capture by over four orders of magnitude. This mechanism causes long (micrometer) charge-pair diffusion lengths crucial for flat-heterojunction photovoltaics. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Formamidinium lead trihalide: A broadly tunable perovskite for efficient planar heterojunction solar cells
Energy and Environmental Science 7:3 (2014) 982-988