Browsing by Author "Taghavinia, Nima"

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Ag Doping of Organometal Lead Halide Perovskites: Morphology Modification and p-Type Character
(2017-02-23)
Shahbazi, Saeed
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Tsai, Cheng-Min
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Narra, Sudhakar
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Wang, Chi-Yung
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Shiu, Hau-Shiang
We report a simple synthetic approach to grow uniform CH3NH3PbI3 perovskite (PSK) layers free of pinholes via ciE varied portions of silver iodide (AgI) added to the precursor solution. XRD/EDS elemental mapping experiments demonstrated nearly uniform Ag distribution inside the perovskite film. When the 1% AgI- assisted perovskite films were fabricated into a p-i-n planar device, the a) photovoltaic performance was enhanced by similar to 30% (PCE increased from 9.5% to 12.0%) relative to the standard cell without added AgI. . Measurement of electronic properties using a hall setup indicated that perovskite films show p-type character after Ag doping, whereas the film is n-type without Ag. Transients of photoluminescence of perovskite films with and without AgI additive deposited on glass, p-type (PEDOT:PSS), and n-type (TiO2) contact layers were recorded with a time-correlated single-photon counting (TCSPC) technique. The TCSPC results indicate that addition of AgI inside perovskite in contact with PEDOT:PSS accelerated the hole-extraction motion whereas that in contact with TiO2 led to a decelerated electron extraction, in agreement with the trend observed from the photovoltaic results. The silver cationic dopant inside the perovskite films had hence an effect of controlling the morphology to improve photovoltaic performance for devices with p-i-n configuration.
Application of a dual functional luminescent layer to enhance the light harvesting efficiency of dye sensitized solar cell
(2017-02-01)
Hosseini, Zahra
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Taghavinia, Nima
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Diau, Eric Wei-Guang
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應用化學系
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應用化學系分子科學碩博班
A luminescent coating of CaAlSiN3:Eu2+ particles applied on photoanode (TiO2) layer of SQ1 sensitized solar cell by doctor blading the paste of phosphor particles. The luminescent layer acted as a dual functional layer and enhanced the short circuit current density (J(SC)) by 64% via both scattering effect and downshifting of the photons in 400-600 nm spectral range to photons in 600-800 nm spectral range. Considerable relative enhancement in incident photon to current conversion efficiency (IPCE) up to 350% in 400-600 run spectral range proves the down shifting effect as the dominant factor for the improved performance of dye sensitized solar cell (DSSC).
Assessment of Luminescent Downshifting Layers for the Improvement of Light-Harvesting Efficiency in Dye-Sensitized Solar Cells
(2014-12-01)
Hosseini, Zahra
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Diau, Eric Wei-Guang
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Mehrany, Khashayar
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Taghavinia, Nima
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應用化學系
Luminescence downshifting (LDS) of light can be a practical photon management technique to compensate the narrow absorption band of high-extinction-coefficient dyes in dye-sensitized solar cells (DSSCs). Herein, an optical analysis on the loss mechanisms in a reflective LDS (R-LDS)/DSSC configuration is reported. For squaraine dye (550-700 nm absorption band) and CaAlSiN3:Eu2+ LDS material (550-700 nm emission band), the major loss channels are found to be non-unity luminescence quantum efficiency (QE) and electrolyte absorption. By using an ideal LDS layer (QE=100%), a less absorbing electrolyte (Co-based), and antireflection coatings, approximately 20% better light harvesting is obtained. If the absorption/emission band of dye/LDS is shifted to 800 nm, a maximal short-circuit current density (J(sc)) of 22.1 mAcm(-2) can be achieved. By putting the LDS layer in front of the DSSC (transmissive mode), more significant loss channels are observed, and hence a lower overall efficiency than the R-LDS configuration.
Enhanced Light Harvesting with a Reflective Luminescent Down-Shifting Layer for Dye-Sensitized Solar Cells
(2013-06-26)
Hosseini, Zahra
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Huang, Wei-Kai
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Tsai, Cheng-Ming
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Chen, Teng-Ming
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Taghavinia, Nima
For a dye-sensitized solar cell with a near-infrared squaraine (SQ1) sensitizer, the photovoltaic performance was enhanced remarkably with a reflective luminescent down-shifting (R-LDS) layer to increase the light-harvesting efficiency at the wavelength region 400-550 nm where the SQ1 dye has weak absorption. Relative enhancements greater than 200% in IPCE near 500 nm and 40-54% in J(SC) were achieved with red phosphor CaAlSiN3:Eu2+ as the LDS material, attaining 5.0 and 4.8% overall efficiencies of power conversion for the R-LDS layer coated on the counter electrode (front illumination) and working electrode (back illumination), respectively.
Interfacial Investigation on Printable Carbon-Based Mesoscopic Perovskite Solar Cells with NiOx/C Back Electrode
(2017-08-02)
Behrouznejad, Fatemeh
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Tsai, Cheng-Min
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Narra, Sudhakar
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Diau, Eric W. -G.
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Taghavinia, Nima
Solar cells with high efficiency, low cost, and high stability are the target for the new generation of solar cells. A fully printable perovskite (CH3NH3PbI3) solar cell (PSC) with device architecture FTO/TiO2/Al2O3/NiOx/C is fabricated in the current research as a low-cost and relatively stable structure and is investigated to determine how different fabrication factors such as the thickness of the insulating spacer layer (Al2O3) or treatments such as heat and UV-O-3 treatments can affect the interfacial properties of this multilayer mesoporous structure. X-ray photoelectron spectra (XPS) show that UV-O-3 treatment increases the Ni3+ (Ni2O3) phase on the surface of the black nickel oxide layer leading to better charge extraction and increasing open-circuit voltage (V-OC) up to 0.945 V. We observe improved CH3NH3PbI3 formation inside the mesoporous layers by the PbI2 penetration at a higher temperature. Impedance spectral together with current-voltage measurements show the effect of thickness for the insulator layer in the internal and interfacial resistances and photovoltaic characteristics of the cell. The best performance of the carbon-based PSC attains power conversion efficiency of 12.1% with the thickness of the Al2O3 layer at 450 nm.
Luminescent Spectral Conversion to Improve the Performance of Dye-Sensitized Solar Cells
(2017-12-06)
Hosseini, Zahra
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Taghavinia, Nima
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Diau, Eric Wei-Guang
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應用化學系
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應用化學系分子科學碩博班
Relative to the broadband solar spectrum, a narrow range of spectral absorption of photovoltaic (PV) devices is considered an important determinant that the efficiency of light harvesting of these devices is less than unity. Having the narrowest spectral response to solar radiation among all PV devices, dye-sensitized solar cells (DSSCs) suffer severely from this loss. Luminescent spectral conversion provides a mechanism to manipulate and to adapt the incident solar spectrum by converting, through photoluminescence, the energies of solar photons into those that are more effectively captured by a PV device. This mechanism is particularly helpful for DSSCs because there is much flexibility in both the choice of the light-harvesting materials and the architecture of the DSSC. Here we review and discuss recent advances in the field of luminescent spectral conversion for DSSCs. The focus is on the architectural design of DSSCs, and the complications, advantages and new functionalities offered by each of their configurations are discussed. The loss mechanisms are examined and important parameters governing the spectral conversion mechanism of a DSSC are introduced.