Sujin Byun

Photoluminescence enhancement in CdS quantum dots by thermal annealing

The photoluminescence behavior of CdS quantum dots in initial growth stage was studied in connection with an annealing process. Compared to the as-synthesized CdS quantum dots (quantum efficiency ≅ 1%), the heat-treated sample showed enhanced luminescence properties (quantum efficiency ≅ 29%) with a narrow band-edge emission. The simple annealing process diminished the accumulated defect states within the nanoparticles and thereby reduced the nonradiative recombination, which was confirmed by diffraction, absorption, and time-resolved photoluminescence. Consequently, the highly luminescent and defect-free nanoparticles were obtained by a facile and straightforward process.

A simple template-free 'sputtering deposition and selective etching' process for nanoporous thin films and its application to dye-sensitized solar cells

A facile and straightforward method is suggested to synthesize nanoporous-TiO₂ thin films for dye-sensitized solar cells (DSSCs). Silver/TiO₂ co-sputtering led to the formation of nanocomposite films which consisted of silver nanoclusters with surrounding TiO₂ matrices, and metal particles were subsequently etched by just immersing in nitric acid. Nanoporous-TiO₂ DSSCs fabricated by this simple and effective process showed power-conversion efficiencies of up to 3.4% at a thickness of only 1.8 μm, which is much superior to that of conventional nanoparticulate-TiO₂ DSSCs with similar thickness.