Oxygen non-stoichiometry in TiO2 and ZnO nano rods: Effect on the photovoltaic properties of dye and Sb2S3 sensitized solar cells. (October 2019)

• Record Type: Journal Article
• Authors: Sharma, Vikas; Das, Tapan Kumar; Ilaiyaraja, P.; Sudakar, C.
• Is Part Of: Solar energy. Volume 191(2019)
• Page Start: 400
• Page End: 409
• Publication Date: 2019-10
• Subjects: Nanorod -- TiO2 -- ZnO -- Photoanode -- Oxygen vacancy -- Efficiency -- Solar cell; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2019.09.009
• Languages: English
• ISSNs: 0038-092X

Abstract

Graphical abstract: Highlights: Oxygen vacancy in TiO2 and ZnO nanorods are tweaked on hydrogen annealing. EPR studies substantiate increased defect concentration in oxides on hydrogenation. Two order increase in photoconductivity in ZnO and TiO2 nanorods result due to OV. Dye and Sb2 S3 semiconductor sensitized solar cell devices demonstrate the effect of OV. OV enhances efficiency with ZnO whereas decreases with TiO2 nanorod-photoanode. Abstract: Rutile TiO2 (TiO2 -NR) and ZnO (ZnO-NR) in nanorod microstructural forms are synthesized by hydrothermal route. The oxides are grown directly on fluorine doped SnO2 coated glass, and annealed in air (AA) and hydrogen (HA) atmosphere for 3 h at 450 °C. A detailed structural, optical, and microstructural study confirms the phase formation in the AA and stability in HA samples. EPR signal with g -values of ~1.99 and ~1.95 from TiO2 -NR and ZnO-NR photoanodes respectively confirms the presence of oxygen vacancy (OV ) related defects. The EPR signals are stronger in TiO2 -NR-HA compared to TiO2 -NR-AA and is absent in ZnO-NR-AA suggesting increased defect concentration on hydrogenation. Further this leads to two order increase in photoconductivity for hydrogenated TiO2 -NR-HA and ZnO-NR-HA photoanodes when measured under 1 Sun illumination compared to AA photoanodes. Photovoltaic power conversion efficiency for both dye and Sb2 S3 sensitized solar cells are found to increase by 2 to 3 times in hydrogenated ZnO-NR. In contrast, TiO2 -NR show two-fold decrease in efficiency on hydrogenation. The efficiency change is consistent with the change in interface impedance, which increases for dye or Sb2 S3 sensitized TiO2 -NR-HA photoanode, whereas, decreases for sensitized ZnO-NR-HA photoanode. These studies show that despite of one to two to three order increase in photoconductivity, the sensitizer/photoanode interface impedance play a significant role in deciding the efficiency.