High charge mobility in two-dimensional percolative networks of PbSe quantum dots connected by atomic bonds

Two-dimensional networks of quantum dots connected by atomic bonds have an electronic structure that is distinct from that of arrays of quantum dots coupled by ligand molecules. We prepared atomically coherent two-dimensional percolative networks of PbSe quantum dots connected via atomic bonds. Here, we show that photoexcitation leads to...

Highly efficient carrier multiplication in PbS nanosheets

Semiconductor nanocrystals are promising for use in cheap and highly efficient solar cells. A high efficiency can be achieved by carrier multiplication (CM), which yields multiple electron-hole pairs for a single absorbed photon. Lead chalcogenide nanocrystals are of specific interest, since their band gap can be tuned to be optimal to exploit...

Disorder strongly enhances Auger recombination in conductive quantum-dot solids

Auger recombination (AR) can be an important loss mechanism for optoelectronic devices, but it is typically not very efficient at low excitation densities. Here we show that in conductive quantum-dot solids, AR is the dominant charge carrier decay path even at excitation densities as low as 10?3 per quantum dot, and that AR becomes faster as the...

High charge-carrier mobility enables exploitation of carrier multiplication in quantum-dot films

Carrier multiplication, the generation of multiple electron–hole pairs by a single photon, is of great interest for solar cells as it may enhance their photocurrent. This process has been shown to occur efficiently in colloidal quantum dots, however, harvesting of the generated multiple charges has proved difficult. Here we show that by tuning...

Increased carrier generation rate in Si nanocrystals in SiO2 investigated by induced absorption

We report on investigations of optical generation of carriers in Si nanocrystals embedded in SiO2 matrix by time-resolved induced absorption technique. Results obtained for excitation below and above twice the bandgap energy h??<?2Eg and h??>?2Eg show very similar decay characteristics (within ?resolution ? 100 fs). When intensity of the signal...

Erratum: Interpretation of ultrafast pump-probe terahertz experiments in the time domain: How to exploit two-dimensional correlations [Phys. Rev. B 83, 205111 (2011)]

Conductive response of a photo-excited sample in a radio-frequent driven resonance cavity

An expression is derived for the perturbative response of a lumped resonance circuit to a sudden change in the circuit parameters. This expression is shown to describe also the photo-induced conductivity of a semiconductor mounted in a single-mode microwave cavity. The power dissipated in the cavity is measured in the two dimensions...

Interpretation of ultrafast pump-probe terahertz experiments in the time domain: How to exploit two-dimensional correlations

Optical-pump-terahertz-probe spectroscopy has the potential to distinguish between several classes of carrier motion, among others high-frequency oscillatory motion, free motion, and quasifree motion within bounded domains. We present a simplified formalism, applicable to thin samples, which allows identification of these three classes of...

Thin-sample limit for time-resolved terahertz spectroscopy

The retrieval of the primary (subpicosecond) photoproducts in small-band two-dimensional time-domain terahertz spectroscopy has succeeded only in a few model systems, due to the complicated correlation between the two time parameters. We show that the nature of the primary photoproducts is revealed upon differentiating the measured time-domain...

Probing formally forbidden optical transitions in PbSe nanocrystals by time- and energy-resolved transient absorption spectroscopy

The first two peaks of the optical extinction spectrum of PbSe nanocrystals in solution have been assigned in the literature to the 1Sh1Se and 1Ph1Pe transitions. In the present work we assign the transitions causing extinction in the energy region between these two lowest-energy peaks. Our femtosecond transient absorption data indicate that...

Retrieving the susceptibility from time-resolved terahertz experiments

We present an analytical expression for the observed signal in time- and phase-resolved pump-probe studies, with particular emphasis on terahertz time-domain spectroscopy. Maxwell’s equations are solved for the response of damped, harmonic oscillators to a driving probe field in the perturbative regime. Our analytical expressions agree with the...

Electron diffusion in polymer: Fullerene bulk heterojunctions

Simultaneous ultrafast probing of intramolecular vibrations and photoinduced charge carriers in rubrene using broadband time-domain THz spectroscopy

Effect of intermolecular disorder on the intrachain charge transport in ladder-type poly( p -phenylenes)

High intrachain hole mobility on molecular wires of ladder-type poly(p-Phenylenes)

Efficiency of Exciton and Charge Carrier Photogeneration in a Semiconducting Polymer

Ultrafast charge generation in a semiconducting polymer studied with THz emission spectroscopy