Harnessing low energy photons is of paramount importance for multi-junction high efficiency solar cells as well as for thermo-photovoltaic applications. However, semiconductor absorbers with bandgap lower than 0.8 eV have been limited to III-V (InGaAs) or IV (Ge) semiconductors that are characterized by high manufacturing costs and complicated lattice matching requirements in their growth and integration with the higher bandgap cells. Here, we have developed solution processed low bandgap photovoltaic devices based on PbS colloidal quantum dots (CQDs) with a bandgap of 0.7 eV suited for both thermo-photovoltaic as well as low energy solar photon harvesting. By matching the spectral response of those cells to that of the infrared solar spectrum, we report a record high short circuit current (JSC) of 37 mA/cm 2 under full solar spectrum and 5.5 mA/cm2 when placed at the back of a silicon wafer resulting in power conversion efficiencies (PCE) of 6.4 % and 0.7 % respectively. Moreover, the device reached an above bandgap PCE of ~6 % as a thermo-photovoltaic cell recorded under a 1000 °C blackbody radiator. * Corresponding Author: Gerasimos.Konstantatos@icfo.e †Electronic Supplementary Information (ESI) available: Experimental section of CQS synthesis and device fabrication; Simulated PbS CQDs solar cells' EQE curves; asobtained PbS CQDs characterizations; the selection of electron blocking layer for 0.7 eV PbS CQDs solar cells; additional device performance tables. See
We
present a new technique, light-induced triplet–triplet
electron resonance spectroscopy (LITTER), which measures the dipolar
interaction between two photoexcited triplet states, enabling both
the distance and angular distributions between the two triplet moieties
to be determined on a nanometer scale. This is demonstrated for a
model bis-porphyrin peptide that renders dipolar traces with strong
orientation selection effects. Using simulations and density functional
theory calculations, we extract distance distributions and relative
orientations of the porphyrin moieties, allowing the dominant conformation
of the peptide in a frozen solution to be identified. LITTER removes
the requirement of current light-induced electron spin resonance pulse
dipolar spectroscopy techniques to have a permanent paramagnetic moiety,
becoming more suitable for in-cell applications and facilitating access
to distance determination in unmodified macromolecular systems containing
photoexcitable moieties. LITTER also has the potential to enable direct
comparison with Förster resonance energy transfer and combination
with microscopy inside cells.
A novel PtIV azido triazolato complex exists as an equilibrium between two species in d3-MeCN and evolves azide radicals (but not hydroxide radicals) when irradiated with visible light.
We
explore the potential of orientation-resolved pulsed dipolar
spectroscopy (PDS) in light-induced versions of the experiment. The
use of triplets as spin-active moieties for PDS offers an attractive
tool for studying biochemical systems containing optically active
cofactors. Cofactors are often rigidly bound within the protein structure,
providing an accurate positional marker. The rigidity leads to orientation
selection effects in PDS, which can be analyzed to give both distance
and mutual orientation information. Herein we present a comprehensive
analysis of the orientation selection of a full set of light-induced
PDS experiments. We exploit the complementary information provided
by the different light-induced techniques to yield atomic-level structural
information. For the first time, we measure a 2D frequency-correlated
laser-induced magnetic dipolar spectrum, and we are able to monitor
the complete orientation dependence of the system in a single experiment.
Alternatively, the summed spectrum enables an orientation-independent
analysis to determine the distance distribution.
We present a new photoswitchable spin label for light-induced pulsed electron paramagnetic resonance dipolar spectroscopy (LiPDS), the photoexcited triplet state of erythrosin B (EB), which is ideal for biological applications. With this label, we perform an in-depth study of the orientational effects in dipolar traces acquired using the refocused laser-induced magnetic dipole technique to obtain information on the distance and relative orientation between the EB and nitroxide labels in a rigid model peptide, in good agreement with density functional theory predictions. Additionally, we show that these orientational effects can be averaged to enable an orientation-independent analysis to determine the distance distribution. Furthermore, we demonstrate the feasibility of these experiments above liquid nitrogen temperatures, removing the need for expensive liquid helium or cryogen-free cryostats. The variety of choices in photoswitchable spin labels and the affordability of the experiments are critical for LiPDS to become a widespread methodology in structural biology.
A novel PtIV triazolato azido complex [3]-[N1,N3] has been synthesised via a strain-promoted double-click reaction (SPDC) between a PtIV azido complex (1) and the Sondheimer diyne (2).
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