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Nikolai Tsvetkov
Solar Energy Conversion Laboratory, Institute of Biochemical Physics RAS, 119334 Moscow, Russia

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Journal article
Published: 10 February 2020 in Nanomaterials
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The performance of dye-sensitized solar cells (DSCs) critically depends on the efficiency of electron transport within the TiO2-dye-electrolyte interface. To improve the efficiency of the electron transfer the conventional structure of the working electrode (WE) based on TiO2 nanoparticles (NPs) was replaced with TiO2 nanotubes (NTs). Sol-gel method was used to prepare undoped and Nb-doped TiO2 NPs and TiO2 NTs. The crystallinity and morphology of the WEs were characterized using XRD, SEM and TEM techniques. XPS and PL measurements revealed a higher concentration of oxygen-related defects at the surface of NPs-based electrodes compared to that based on NTs. Replacement of the conventional NPs-based TiO2 WE with alternative led to a 15% increase in power conversion efficiency (PCE) of the DSCs. The effect is attributed to the more efficient transfer of charge carriers in the NTs-based electrodes due to lower defect concentration. The suggestion was confirmed experimentally by electrical impedance spectroscopy measurements when we observed the higher recombination resistance at the TiO2 NTs-electrolyte interface compared to that at the TiO2 NPs-electrolyte interface. Moreover, Nb-doping of the TiO2 structures yields an additional 14% PCE increase. The application of Nb-doped TiO2 NTs as photo-electrode enables the fabrication of a DSC with an efficiency of 8.1%, which is 35% higher than that of a cell using a TiO2 NPs. Finally, NTs-based DSCs have demonstrated a 65% increase in the PCE value, when light intensity was decreased from 1000 to 10 W/m2 making such kind device be promising alternative indoor PV applications when the intensity of incident light is low.

ACS Style

Nikolai Tsvetkov; Liudmila Larina; Jeung Ku Kang; Oleg Shevaleevskiy. Sol-Gel Processed TiO2 Nanotube Photoelectrodes for Dye-Sensitized Solar Cells with Enhanced Photovoltaic Performance. Nanomaterials 2020, 10, 296 .

AMA Style

Nikolai Tsvetkov, Liudmila Larina, Jeung Ku Kang, Oleg Shevaleevskiy. Sol-Gel Processed TiO2 Nanotube Photoelectrodes for Dye-Sensitized Solar Cells with Enhanced Photovoltaic Performance. Nanomaterials. 2020; 10 (2):296.

Chicago/Turabian Style

Nikolai Tsvetkov; Liudmila Larina; Jeung Ku Kang; Oleg Shevaleevskiy. 2020. "Sol-Gel Processed TiO2 Nanotube Photoelectrodes for Dye-Sensitized Solar Cells with Enhanced Photovoltaic Performance." Nanomaterials 10, no. 2: 296.

Journal article
Published: 21 January 2020 in Sustainability
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In mesoscopic perovskite solar cells (PSCs) the recombination processes within the TiO2 photoelectrode and at the TiO2/perovskite interface limit power conversion efficiency. To overcome this challenge, we investigated the effect of TiO2 phase composition on the electronic structure of TiO2 photoelectrodes, as well as on PSCs performance. For this, a set of PSCs based on TiO2 thin films with different content of anatase and rutile particles was fabricated under ambient conditions. X-ray diffraction, optical spectroscopy and scanning electron microscopy were used to study the structural, morphological and optical characteristics of TiO2 powders and TiO2-based thin films. X-ray photoelectron spectroscopy (XPS) analysis of anatase revealed a cliff conduction band alignment of 0.2 eV with respect to the rutile. Energy band alignment at the anatase/rutile/perovskite interfaces deduced from the XPS data provides the possibility for interparticle electron transport from the rutile to anatase phase and the efficient blocking of electron recombination at the TiO2/perovskite interface, leading to efficient electron-hole separation in PSCs based on mixed-phase TiO2 photoelectrodes. PSCs based on TiO2 layers with 60/40 anatase/rutile ratio were characterized by optimized charge extraction and low level of recombination at the perovskite/TiO2 interface and showed the best energy conversion efficiency of 13.4% among the studied PSCs. Obtained results provide a simple and effective approach towards the development of the next generation high efficiency PSCs.

ACS Style

Anna Nikolskaia; Marina Vildanova; Sergey Kozlov; Nikolai Tsvetkov; Liudmila Larina; Oleg Shevaleevskiy. Charge Transfer in Mixed-Phase TiO2 Photoelectrodes for Perovskite Solar Cells. Sustainability 2020, 12, 788 .

AMA Style

Anna Nikolskaia, Marina Vildanova, Sergey Kozlov, Nikolai Tsvetkov, Liudmila Larina, Oleg Shevaleevskiy. Charge Transfer in Mixed-Phase TiO2 Photoelectrodes for Perovskite Solar Cells. Sustainability. 2020; 12 (3):788.

Chicago/Turabian Style

Anna Nikolskaia; Marina Vildanova; Sergey Kozlov; Nikolai Tsvetkov; Liudmila Larina; Oleg Shevaleevskiy. 2020. "Charge Transfer in Mixed-Phase TiO2 Photoelectrodes for Perovskite Solar Cells." Sustainability 12, no. 3: 788.

Research article
Published: 30 October 2019 in ACS Applied Energy Materials
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Perovskite halides are of great attraction as efficient light absorption materials for solid-state solar cells, but the stability and photovoltaic energy conversion efficiency of perovskite solar cell (PSCs) are still limited by the interface structures and defects between their light-absorbing perovskite halides and electron transport layers (ETLs). Here, we report the ultraviolet (UV) light-induced degradation mechanism at the interfaces between perovskite halide and conventional TiO2 ETL materials, and provide a solution to overcome this drawback. UV-induced degradation is shown to be attributed to the formation of oxygen vacancies formed at the perovskite halide-ETL interface under UV light illumination, where the oxygen atoms released at the interface accelerate the decomposition of perovskite halide by inducing chemical reactions. Meanwhile, nanocrystalline SrTiO3 (STO) ETLs are revealed to be tunable in enabling high performance in PSCs under UV light illumination. Indeed, tuning the electronic structure of STO ETLs by Nb doping, in combination with the controllable removal of SrO phases segregated on the Nb-doped STO ETL surfaces, is exhibited to enable robust interface stability and stable high photovoltaic energy conversion efficiency for PSCs. Furthermore, we demonstrate that STO-based PSCs have no hysteresis due to low defect concentrations at the perovskite halide-STO ETL interfaces.

ACS Style

Nikolai Tsvetkov; Byeong Cheul Moon; Jiyoung Lee; Jeung Ku Kang. Controlled Synthesis of Nanocrystalline Nb:SrTiO3 Electron Transport Layers for Robust Interfaces and Stable High Photovoltaic Energy Conversion Efficiency in Perovskite Halide Solar Cells. ACS Applied Energy Materials 2019, 3, 344 -351.

AMA Style

Nikolai Tsvetkov, Byeong Cheul Moon, Jiyoung Lee, Jeung Ku Kang. Controlled Synthesis of Nanocrystalline Nb:SrTiO3 Electron Transport Layers for Robust Interfaces and Stable High Photovoltaic Energy Conversion Efficiency in Perovskite Halide Solar Cells. ACS Applied Energy Materials. 2019; 3 (1):344-351.

Chicago/Turabian Style

Nikolai Tsvetkov; Byeong Cheul Moon; Jiyoung Lee; Jeung Ku Kang. 2019. "Controlled Synthesis of Nanocrystalline Nb:SrTiO3 Electron Transport Layers for Robust Interfaces and Stable High Photovoltaic Energy Conversion Efficiency in Perovskite Halide Solar Cells." ACS Applied Energy Materials 3, no. 1: 344-351.