We report the fabrication and measurement of solar cells approaching a power conversion efficiency of 3.2% using a low band gap conjugated polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] and CdSe nanoparticles. These devices exhibit an external quantum efficiency (EQE) of >30% in a broad range of 350-800 nm with a maximum EQE of 55% in a range of 630-720 nm. We also present certified device efficiencies of 3.13% under AM 1.5 illumination.

We present a study of the self-assembly, charge-transfer kinetics, and catalytic properties of hybrid complexes of CdTe nanocrystals (nc-CdTe) and Clostridium acetobutylicum [FeFe]-hydrogenase I (H(2)ase). Molecular assembly of nc-CdTe and H(2)ase was mediated by electrostatic interactions and resulted in stable, enzymatically active complexes. The assembly kinetics was monitored by nc-CdTe photoluminescence (PL) spectroscopy and exhibited first-order Langmuir adsorption behavior. PL was also used to monitor the transfer of photogenerated electrons from nc-CdTe to H(2)ase. The extent to which the intramolecular electron transfer (ET) contributed to the relaxation of photoexcited nc-CdTe relative to the intrinsic radiative and nonradiative (heat dissipation and surface trapping) recombination pathways was shown by steady-state PL spectroscopy to be a function of the nc-CdTe/H(2)ase molar ratio. When the H(2)ase concentration was lower than the nc-CdTe concentration during assembly, the resulting contribution of ET to PL bleaching was enhanced, which resulted in maximal rates of H(2) photoproduction. Photoproduction of H(2) was also a function of the nc-CdTe PL quantum efficiency (PLQE), with higher-PLQE nanocrystals producing higher levels of H(2), suggesting that photogenerated electrons are transferred to H(2)ase directly from core nanocrystal states rather than from surface-trap states. The duration of H(2) photoproduction was limited by the stability of nc-CdTe under the reactions conditions. A first approach to optimization with ascorbic acid present as a sacrificial donor resulted in photon-to-H(2) efficiencies of 9% under monochromatic light and 1.8% under AM 1.5 white light. In summary, nc-CdTe and H(2)ase spontaneously assemble into complexes that upon illumination transfer photogenerated electrons from core nc-CdTe states to H(2)ase, with low H(2)ase coverages promoting optimal orientations for intramolecular ET and solar H(2) production.

Quantum dots have emerged as an important class of material that offers great promise to a diverse range of applications ranging from energy conversion to biomedicine. Here, we review the potential of using quantum dots and quantum dot conjugates as sensitizers for photodynamic therapy (PDT). The photophysics of singlet oxygen generation in relation to quantum dot-based energy transfer is discussed and the possibility of using quantum dots as photosensitizer in PDT is assessed, including their current limitations to applications in biological systems. The biggest advantage of quantum dots over molecular photosensitizers that comes into perspective is their tunable optical properties and surface chemistries. Recent developments in the preparation and photophysical characterization of quantum dot energy transfer processes are also presented in this review, to provide insights on the future direction of quantum dot-based photosensitization studies from the viewpoint of our ongoing research.