title: Photovoltaic effects of CdS and PbS quantum dots encapsulated in zeolite Y.
abstract: Zeolite Y films (0.35-2.5 μm), into which CdS and PbS quantum dots (QDs) were loaded, were grown on ITO glass. The CdS QD-loaded zeolite Y films showed a photovoltaic effect in the electrolyte solution consisting of Na(2)S (1 M) and NaOH (0.1 M) with Pt-coated F-doped tin oxide glass as the counter electrode. In contrast, the PbS QD-loaded zeolite Y films exhibited a negligible PV effect. This contrasting behavior was proposed to arise from the large difference in driving force for the electron transfer from S(2-) in the solution to the hole in the valence band of QDs, with the former being much larger (~2 eV) than the latter (~1 eV). In the case of CdS QD-loaded zeolite Y with a loaded amount of CdS of 6.3 per unit cell, the short circuit current, open circuit voltage, fill factor, and efficiency were 0.3 mA cm(-2), 423 V, 28, and 0.1%, respectively, under the AM 1.5, 100 mW cm(-2) condition. This cell was stable for more than 18 days of continuous measurements. A large (3-fold) increase in overall efficiency was observed when PbS QD-loaded zeolite Y on ITO glass was used as the counter electrode. This phenomenon suggests that the uphill electron transfer from ITO glass to S in the solution is facilitated by the photoassisted pumping of the potential energy of the electron in ITO glass to the level that is higher than the reduction potential of S by PbS QDs. Under this condition, the incident-photon-to-current conversion efficiency (IPCE) value at 398 nm was 42% and the absorbed-photon-to-current conversion efficiency (APCE) value at 405 nm was 82%. The electrolyte-mediated interdot charge transport within zeolite films is concluded to be responsible for the overall current flow.
authors: Korea Center for Artificial Photosynthesis, Center for Nano Materials, Department of Chemistry, Sogang University, Seoul 121-742, Korea.
authors: Hyun Sung
authors: HS
authors: Kim
authors: Nak Cheon
authors: NC
authors: Jeong
authors: Kyung Byung
authors: KB
authors: Yoon
mesh_terms: D019187:Cadmium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D010777:Photochemistry; D045663:Quantum Dots; D013440:Sulfides / Q000138:chemical synthesis / Q000737:chemistry*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D013440:Sulfides; C034939:cadmium sulfide; D017641:Zeolites; C018391:lead sulfide; D007854:Lead