Choong-Sun Lim

Performance improvement of Sb2S3-sensitized solar cell by introducing hole buffer layer in cobalt complex electrolyte

We found that the insertion of the poly-3-hexylthiophene (P3HT) layer into the pristine device results in great improvement of the efficiency, from 2.0% to 3.3% at 1 sun illumination. The improvement was mainly attributed to the improved fill factor, which for the Sb2S3 sensitized solar cell was seriously degraded from 56.0% (at 0.1 sun) to 31.5% (at 1 sun), whereas the fill factor of the Sb2S3/P3HT sensitized solar cell was only moderately degraded, from 59.3% (at 0.1 sun) to 40.4%. The role of P3HT as a hole buffer layer was analyzed by electrochemical impedance spectroscopy (EIS).

Hole-conducting mediator for stable Sb2S3-sensitized photoelectrochemical solar cells

Iodide redox (3I−/I3−), polysulfide redox (S2−/Sx2−), organic redox [TMTU/TMFDS2+: tetramethylthiourea/tetramethylformaminium-bis(trifluoromethanesulfonyl)imide], ferrocene redox (Fc/Fc+), nickel redox [Ni(II)/Ni(III)], and cobalt redox [Co(II)/Co(III)] hole conducting electrolytes were systematically investigated to determine their suitability for use in Sb2S3-sensitized photoelectrochemical solar cells. A long-term stability test and UV-visible spectral analyses revealed that Sb2S3-sensitized photoelectrochemical solar cells worked stably with Co(II)(o-phen)3(TFSI)2/Co(III)(o-phen)3(TFSI)3 [TFSI: bis(trifluoromethanesulfonyl)imide] as the redox mediator.

Synthesis of uniform PS-b-P2VP nanoparticles via reprecipitation and their use as sacrificial templates for inorganic hollow nanoparticles

Uniform PS-b-P2VP (polystyrene-block-poly-2-vinylpyridine) block copolymer nanoparticles were successfully synthesized using a simple reprecipitation method. The PS-b-P2VP nanoparticles could serve as sacrificial templates to generate silica and titania hollow nanoparticles of ∼100 nm size.

Robust and scale-up synthesis of hollow TiO2 nanospheres with sub-100-nm scale by templating of PS-b-P2VP nanospheres

Abstract

Synthesis of PS-b-P2VP di-block copolymer particles with internal structure via simple reprecipitation method

The polystyrene-block-poly-2-vinylpyridine (PS-b-P2VP) di-block copolymer nanoparticles with onionlike internal structure have been synthesized by a simple reprecipitation method under stirring. The internal structures of the di-block copolymer nanoparticles were dependent on kinetic process in the reprecipitation method such as morphology quenching. Relatively quick reprecipitation conditions produced transient morphologies such as random-onion core-shell or random/cylindrical internal structure, while the slow reprecipitation conditions yielded the onion-like internal morphology. By adjusting the combination of common solvent and poor solvent, we could control the internal morphology of d-BCP nanoparticles in the simple reprecipitation method. In addition, we could synthesize porous titanium oxide nanoparticles by templating the d-BCP nanoparticles with internal structure.

Origin of Nonlinear Device Performance with Illuminated Sun Intensity in Mesoscopic Sb2S3-sensitized Photoelectrochemical Solar Cells using Cobalt Electrolyte

ABSTRACT: The mesoscopic Sb 2 S 3 -sensitized photoelectrochemical solar cells using cobalt redox electrolyteexhibit nonlinear behavior of power conversion efficiency with illuminated sun intensity. From themeasurement of bulk diffusion and electrochemical impedance spectroscopy studies, we suggestthat the nonlinearity of device performance with illuminated sun intensity is attributed not to theslow bulk diffusion problem of cobalt electrolyte but to the limited mass transport in narrowed porevolume in mesoscopic TiO 2 electrode.Keywords : Sb 2 S 3 , Photoelectrochemical solar cell, TiO 2 , Cobalt electrolyte Received September 15, 2011: Accepted September 29, 2011 1. Introduction Since Gratzel et al. 1) reported a mesoscopic dye-sensitized photoelectrochemical solar cell with highpower conversion efficiency over 11% at 1 sun illumination,the sensitized photoelectrochemical solar cells have beenintensively studied due to their distinguished device structurefrom conventional p-n heterojunction solar cells. The sensi-tized solar cells are comprised to mesoscopic photoanode,sensitizer, and redox electrolyte which has correspondingrole of electron conductor, light absorber, and hole con-ductor, respectively. This unique device architecture enablesthe sensitized solar cells to hold cost-effectiveness.Recently inorganic semiconductors have been con-sidered as a promising alternative of conventional dyesbecause of their peculiar properties such as easy chargeseparation by higher dipole moment, ~10 fold higherextinction coefficient than Ru/organic dyes, convenientbandgap tunability by size control, and multiple excitongeneration.