Effect of Er3+ and Yb3+ co-doping on the performance of a ZnO-based DSSC

• Published in: Journal of the Korean Physical Society 2016, 68(12), , pp.1381-1389
• Main Authors: Tsege, Ermias Libnedengel, Vu, Hong Ha Thi, Atabaev, Timur Sh, Kim, Hyung-Kook, Hwang, Yoon-Hwae
• Format: Article
• Language: English
• Subjects: Mathematical and Computational Physics; Particle and Nuclear Physics; Physics; Physics and Astronomy; Theoretical; 물리학
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.68.1381

Zinc-oxide (ZnO) nanoparticles (NPs) co-doped with different concentrations of rare-earth ions of erbium and ytterbium, (ZnO: Er 3+ , Yb 3+ ) were synthesized for applications to ZnO-based dye sensitized solar cells (DSSC). The composite NPs used for the photoelectrode (PE) were synthesized using a simple co-precipitation technique. X-ray diffraction and scanning electron microscopy measurements on the prepared samples revealed a single phase wurzite ZnO powder with approximate sizes in the range from 15 to 20 nm. Photoluminescence (PL) measurements confirmed that the synthesized composite NPs had a good up-conversion (UPC) property. The prepared powders were directly used to make PEs for DSSCs. The photovoltaic efficiency of the DSSCs was enhanced compared to that of pure ZnO-based DSSCs. Particularly, the PE made up of ZnO: Er 3+ , Yb 3+ NPs with 4 wt% of Er 3+ and Yb 3+ generates a short-circuit current density ( J sc ) of 4.794 mA·cm −2 and an open circuit voltage ( V oc ) of 0.602 V with an efficiency ( η ) of 1.58%. The result indicates a 48.4% J sc improvement compared to a pure ZnO PE-based DSSC. The photocurrent improvement is due to an increase in the light-harvesting capacity of the PEs attained through the UPC property of ZnO: Er 3+ , Yb 3+ NPs. As confirmed by PL and electrochemical impedance spectra (EIS), the use of ZnO: Er 3+ ,Yb 3+ NPs as PEs for DSSCs enhances charge concentration and transport as a result of n-type doping. However, all ZnO: Er 3+ , Yb 3+ NP based PEs exhibited a lower V oc as a result of a down shift in the Fermi energy, which affects the overall efficiency of the cell.