Recent and forthcoming publications in pss

Evidence of two-photon absorption in strain-free quantum dot GaAs/AlGaAs solar cells

Andrea Scaccabarozzi, Silvia Adorno, Sergio Bietti, Maurizio Acciarri, and Stefano Sanguinetti

An intermediate band solar cell containing high-density, strain-free quantum dots grown by droplet epitaxy is demonstrated to produce photocurrent when two sub-bandgap energy photons are absorbed simultaneously. The quality of the quantum dot/barrier pair – allowed by the absence of strain-related defects, the good confinement, and the capability of droplet epitaxy to grow high-density and large aspect ratio quantum dots – opens new opportunities for quantum dot based solar cells.

Phys. Status Solidi RRL (2013) DOI 10.1002/pssr.201206518

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Improved efficiency of blue phosphorescence organic light-emitting diodes with irregular stepwise-doping emitting layers

Jun Liu, Jing Wang, Saijun Huang, Hsi-An Chen, and Gufeng He

A stepwise doping emitting layer is considered as an effective way to control the charge transport and recombination in organic light-emitting diodes (OLEDs). It has been demonstrated that the irregular stepwise doping profile in the emitting layer can deliver better charge carrier balance and tune the recombination zone away from the low triplet energy electron transporting layer to avoid possible quenching. Both effects improve the efficiency significantly. It is anticipated that this method can also be applied to other emitting systems to realize better performance.

Phys. Status Solidi A (2013) DOI 10.1002/pssa.201228727

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Symmetry breaking and low energy conformational fluctuations in amorphous graphene

Y. Li and D. A. Drabold

Amorphous graphene has a rich and interesting energy landscape. A distinct energy scale of basins (∼10 meV) is observed, associated with different puckered configurations, and then within such a configuration, an ambiguous energy minimum with a continuum of bond angles and bond lengths with an energy scale of few μeV and a nearly flat potential-energy landscape. Within a given puckered configuration, this continuum is much like what was seen for a-Si:H earlier. Vibrational calculations reveal the existence of localized imaginary-frequency modes in a flat 800-atom amorphous graphene model. These modes are localized on pentagons and play the key role in losing planar symmetry and forming pentagonal puckering structures.

Phys. Status Solidi B (2012) DOI 10.1002/pssb.201248481

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