Template assisted nanoporous TiO2 nanoparticles: The effect of oxygen vacancy defects on photovoltaic performance of DSSC and QDSSC. (1st January 2018)

• Record Type: Journal Article
• Authors: Das, Tapan Kumar; Ilaiyaraja, P.; Sudakar, C.
• Is Part Of: Solar energy. Volume 159(2018)
• Page Start: 920
• Page End: 929
• Publication Date: 2018-01-01
• Subjects: Oxygen vacancy -- Nanoporous TiO2 -- DSSC -- QDSSC -- Solar cell -- Photoanode; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2017.11.061
• Languages: English
• ISSNs: 0038-092X

Abstract

Graphical abstract: Highlights: Template assisted synthesis produces doughnut like nanoporus TiO2 nanoparticles. Nanoporous doughnut TiO2 exhibit large light scattering. EPR show strong absorption due to the Ti 3+ -VO -Ti 3+ defect sites. VO significantly reduce the photovoltaic efficiency of DSSC and QDSSC. Abstract: We present a detailed study on the photovoltaic performance of dye and quantum dot (QD) sensitized solar cells fabricated using nanoporous TiO2 photoanodes prepared by a template approach. Nanoporous TiO2 particles (TNPO) are prepared by sol-gel method using dextran (TNPO-D) and glucose (TNPO-G) as templates. The decomposition of templating agents during calcination introduces nanopores (∼10 nm) in TiO2 nanoparticles as evidenced from the HRTEM studies. Oxygen vacancies are also introduced in TiO2 nanoparticles due to prevailing reducing ambient during decomposition. Oxygen vacancy (VO ) related defects are evidenced from EPR spectra from a strong absorption signal observed at g-value of 1.994 related to Ti 3+ -VO -Ti 3+ defect sites. The defect concentration estimated from EPR spectra is found to be ∼5 to 15 times larger for nanoporous TiO2 particles compared to Degussa P25-TiO2 . TNPO samples also show enhanced defect level photoluminescence emission. The photovoltaic efficiency (η) and the IPCE of DSSC and QDSSC are strongly influenced by the defect concentration and seen to decrease with increasing VO in TiO2 nanoparticles. Twofold lower η is found in both DSSC (∼6.38% to 3.66%) and QDSSC (∼1.69% to 0.46%) devices made using nanoporous TiO2 compared to P25-TiO2 photoanode solar cells. P25-TiO2 also shows significant decrease in η when oxygen vacancies are introduced by hydrogen annealing process, which reveal detrimental effect of VO on the photovoltaic properties. EIS studies suggest increased interfacial resistance in solar cells made from nanoporous TiO2 photoanodes.