Browsing by Author "Wu, Hui-Ping"

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A study on utilizing different metals as the back contact of CH3NH3PbI3 perovskite solar cells
(2016)
Behrouznejad, F.
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Shahbazi, S.
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Taghavinia, N.
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Wu, Hui-Ping
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Diau, Eric Wei-Guang
Organic-inorganic halide perovskite solar cells have attracted considerable interest due to their high efficiency and low fabrication cost. Au and Ag are usually used as the back contact metals but have limitations such as Au is too expensive and Ag is unstable. Here, Pt, Au, Ni, Cu, Cr and Ag were studied as the back contact electrodes for perovskite solar cells. We looked at how the work function of metals can affect their photovoltaic characteristics. The compositional and electrical characterizations were studied using X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The general trend observed was that the shunt resistance and open-circuit voltage of the devices decrease with the decreasing work function of the contact metal. The EIS measurements indicated that the internal resistance of the cell decreases when using spiro-OMeTAD in Au, Ag and Pt devices, whereas in the case of Ni, Cu and Cr devices, the internal resistance of the interface increases, indicating that spiro-OMeTAD is not a good HTM with these metal electrodes. Our results also showed that Cu and Ag were not stable in these devices and that the performance of the Ag device degraded faster than that of the Cu device. Efficiencies of 16.4%, 16.5%, 14.7%, 7.8%, 9.2% and 0.04% were obtained for the devices with Au, Ag, Pt, Ni, Cu and Cr, respectively.
Characterisation of electron transport and charge recombination using temporally resolved and frequency-domain techniques for dye-sensitised solar cells
(2012)
Li, Lu-Lin
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Chang, Yu-Cheng
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Wu, Hui-Ping
;
Diau, Eric Wei-Guang
;
應用化學系
We review systematically the kinetic characterisation of electron transport and charge recombination in dye-sensitised solar cells (DSSC) using both temporally resolved and frequency-domain techniques. For the temporally resolved approach, charge extraction (CE), transient-photocurrent decay (TCD) and transient-photovoltage decay (TVD) methods are introduced in detail; for the frequency-domain approach, techniques involving electrochemical impedance spectroscopy (EIS), intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) are presented in detail. The TCD and TVD data are obtained under short-circuit and open-circuit conditions, respectively, and the electron diffusion coefficients and electron lifetimes are extracted from fitting the decay curves accordingly; the IMPS/IMVS results are the counterparts of the TCD/TVD results in the frequency domain. Even though the EIS results are readily acquired, an accurate interpretation of the data requires an appropriate model to determine the internal features of the device. This review provides an account of each technique about its operating principle, experimental setup and data analysis. As case studies for each technique, examples are given to rationalise the observed potential shift, decay coefficients of electron transport and of charge recombination in relation to the corresponding photovoltaic performance of the device.
Cobalt Oxide (CoOx) as an Efficient Hole-Extracting Layer for High Performance Inverted Planar Perovskite Solar Cells
(2016-12-14)
Shalan, Ahmed Esmail
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Oshikiri, Tomoya
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Narra, Sudhakar
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Elshanawany, Mahmoud M.
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Ueno, Kosei
CoOx is a promising hole-extracting layer (HEL) for inverted planar perovskite solar cells with device configuration ITO/CoOx/CH3NH3PbI3/PCBM/Ag. The devices fabricated according to a simple solution procedure showed the best photovoltaic performance attaining power conversion efficiency (PCE) of 14.5% under AM 1.5 G 1 sun irradiation, which is significantly superior to those of materials fabricated with a traditional HEL such as PEDOT:PSS (12.2%), NiOx (10.2%), and CuOx (9.4%) under the same experimental conditions. We characterized the chemical compositions with XPS, crystal structures with XRD, and film morphology with SEM/AFM techniques. Photoluminescence (PL) spectra and the corresponding PL decays for perovskite deposited on varied HEL films were recorded to obtain the hole-extracting characteristics, for which the hole extracting times show the order CoOx (2.8 ns) < PEDOT:PSS (17.5 ns) < NiOx (22.8 ns) < CuOx (208.5 ns), consistent with the trend of their photovoltaic performances. The reproducibility and enduring stability of those devices were examined to show the outstanding long-term stability of the devices made of metal oxide HEL, for which the CoOx device retained PCE approximate to 12% for over 1000 h.
Construction of a photoanode with varied TiO2 nanostructures for a Z907-sensitized solar cell with efficiency exceeding 10%
(2014)
Shiu, Jia-Wei
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Lan, Zih-Jian
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Chan, Chien-Yi
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Wu, Hui-Ping
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Diau, Eric Wei-Guang
For Z907-based dye-sensitized solar cells, we constructed photoanodes, layer by layer, containing titania nanostructures of varied types - spherical nanoparticles (NPs), one-dimensional nanorods (NRs), and octahedron-like nanocrystals of varied size (HD1-HD3), in either a bi-layer (BL) or a multi-layer (ML) film configuration. To understand the kinetics of electron transport in these devices, we measured charge extraction, intensity-modulated photocurrent spectra and photovoltage spectra of devices made of either these nanomaterials or hybrid HD-NP composites (HDP). The HD devices featured an excellent characteristic of electron transport and upward-shifted potentials to produce V-OC greater than those of the NP and NR devices, but the latter featured a larger dye loading to give J(SC) greater than that for the former; the devices fabricated with hybrid HDP films showed enhanced J(SC) and balanced V-OC to perform better than their individual counterparts. We constructed the ML devices based on the NP-BL system with additional HDP layers inserted between the two components, NP and SL, to enhance J(SC) so as to attain the best performance, with efficiency of power conversion (PCE) = 10.1%, at a film thickness (L) of 26 mu m. Because of the robust structural feature of the HD films, the devices fabricated with a simple BL film configuration, HD1/SL = 6/3, exhibited the best performance, PCE = 10.2% at L = 29 mu m, which is a promising advance for Z907-based solar cells with a superior and enduring stability of performance for commercialization.
Control of preferred orientation with slow crystallization for carbon-based mesoscopic perovskite solar cells attaining efficiency 15%
(2017-01-14)
Tsai, Cheng-Min
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Wu, Guan-Wei
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Narra, Sudhakar
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Chang, Hung-Ming
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Mohanta, Nayantara
To produce mesoscopic carbon-electrode-based solar cells free of a hole-conduction layer, we developed a simple one-step drop-cast method (temperature 20 degrees C, relative humidity 50%) to grow uniform and compact perovskite nanocrystals via slow crystallization (SC). X-ray diffraction (XRD) results indicated that perovskite nanocrystals produced inside the mesoporous TiO2/Al2O3/C layers according to our SC approach with N-methyl-2-pyrrolidone (NMP) as a precursor solvent showed a preferred orientation at facet (004) with large crystalline grains, whereas those produced with other solvents or via thermal annealing (TA) methods showed greater intensity at facet (220) with small crystals. After the SC (NMP) procedure was completed, additional TA treatment would change the preferred orientation from (004) back to facet (220), which would break the connectivity and lose the uniformity of the crystals, causing the grains to become significantly smaller. Transient photoluminescence (PL) decay profiles of the SC devices made with four precursor solvents, NMP, g-butyrolactone (GBL), dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), were recorded to show the trend of charge separation kinetics of the perovskite crystals inside the mesoporous films, which is consistent with the trend of the corresponding device performance showing the same order. The SC (NMP) device attained the best efficiency of power conversion (PCE), 15.0%, with average value (13.9 +/- 0.5%), which is much superior to those devices from either the traditional one-step TA (DMF) method (5.2 +/- 1.0%) or the traditional sequential TA method (10.1 +/- 0.7%). This work emphasizes the significance of the control of preferred orientation of perovskite nanocrystals using the SC approach, to obtain high-performance carbon-based mesoscopic solar cells with excellent reproducibility and stability.
Design and characterization of alkoxy-wrapped push-pull porphyrins for dye-sensitized solar cells
(2012)
Ripolles-Sanchis, Teresa
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Guo, Bo-Cheng
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Wu, Hui-Ping
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Pan, Tsung-Yu
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Lee, Hsuan-Wei
Three alkoxy-wrapped push-pull porphyrins were designed and synthesized for dye-sensitized solar cell (DSSC) applications. Spectral, electrochemical, photovoltaic and electrochemical impedance spectroscopy properties of these porphyrin sensitizers were well investigated to provide evidence for the molecular design.
Design and Characterization of Heteroleptic Ruthenium Complexes Containing Benzimidazole Ligands for Dye-Sensitized Solar Cells: The Effect of Fluorine Substituents on Photovoltaic Performance
(1970-01-01)
Huang, Wei-Kai
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Wu, Hui-Ping
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Lin, Pi-Lun
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Lee, Yuan-Pern
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Diau, Eric Wei-Guang
"We designed heteroleptic ruthenium complexes (RD12-RD15) containing fluoro-substituted benzimidazole ligands for dye-sensitized solar cells (DSSCs). These dyes were synthesized according to a typical one-pot procedure with the corresponding ancillary ligands produced in two simple steps; they were prepared into DSSC devices according to the same conditions of fabrication. The eventual devices show a systematic trend of increasing V-OC and decreasing J(SC) with fluorine atoms of increasing number substituted on the ligand. The charge extraction results show that upward shifts of the TiO2 potential occurred when the fluoro-substituted dyes were sensitized on TiO2 with a systematic trend of shift N719 > RD15 (with 5 F) > RD12 (with 2 F) > RD5 (no F); the intensity modulated photovoltage spectra indicate that those fluoro substituents retard charge recombination with the electron lifetimes (tau(R)) in the order RD15 > RD12 > RD5 > N719, consistent with the variation of V-OC for the systems."
Design and Characterization of Heteroleptic Ruthenium Complexes Containing Benzimidazole Ligands for Dye-Sensitized Solar Cells: The Effect of Thiophene and Alkyl Substituents on Photovoltaic Performance
(2013-02-07)
Huang, Wei-Kai
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Wu, Hui-Ping
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Lin, Pi-Lun
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Diau, Eric Wei-Guang
;
應用化學系
We designed heteroleptic ruthenium complexes RD16-RD18 containing fluoro-substituted and thiophene-based benzimidazole ligands for dye-sensitized solar cells. Whereas the substitution of only fluorine in the RD12 device has an effect of enhancing the open-circuit voltage (V-OC), additional substitution of thiophene in the RD16-RD18 sensitizers showed a slightly decreased V-OC. Systematic enhanced short-circuit current density (J(SC)) and efficiency (eta) of power conversion of the devices had the order RD18 > RD17 > RD16 > RD12 > N719, attributed to the increasing light-harvesting ability and the broadened spectral features with thiophene-based ligands. Measurements of charge extraction and intensity-modulated photovoltage spectra indicate that thiophene substitution shifts downward the TiO2 potential and accelerates charge recombination, but inclusion of a long hexyl chain on the thiophene moiety retards charge recombination to account for the variation of V-OC in the series. For a duration test of device performance at ambient temperature, only similar to 2% degradation of cell performance was found for the devices of RD18 and RD12 over 2000 h, but a 10% decrease in overall efficiency was observed in the N719 device.
Detachment and transfer of ordered TiO(2) nanotube arrays for front-illuminated dye-sensitized solar cells
(2011-09-01)
Li, Lu-Lin
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Chen, Yi-Ju
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Wu, Hui-Ping
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Wang, Niann S.
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Diau, Eric Wei-Guang
We report a method of detachment and transfer of one-dimensional TiO(2) nanotube (NT) arrays to fabricate dye-sensitized solar cells (DSSCs) with illumination from the front side. The ordered NT arrays (tube length 20 mm) were detached from the NT-Ti substrate, as annealed, by means of a second anodization at 20 V for 4 h and then transferred, inverted, onto a transparent substrate of conducting oxide (TCO) with an interface of TiO(2) nanoparticles of thickness similar to 2 mu m. Dry etching of the NT surface in a highly dense plasma reactor under BCl(3)/Cl(2) for 90 s opened previously closed ends of the tubes. The inverted (bottom-up) NT-TCO substrate was fabricated into a DSSC device that shows a cell performance (eta = 6.24%) significantly improved over those of a front-illuminated counterpart with an upright (face-up) structure (eta = 4.84%) and of a conventional back-illuminated device (eta = 4.61%). Electrochemical impedance spectra (EIS) of the devices under one-sun irradiation were measured to rationalize the cell performances that are consistent with the corresponding interfacial impedances between the NT arrays and the electrode for collection of electrons.
Detachment and transfer of ordered TiO2 nanotube arrays for front-illuminated dye-sensitized solar cells
(2011-09-01)
Li, Lu-Lin
;
Chen, Yi-Ju
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Wu, Hui-Ping
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Wang, Niann S.
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Diau, Eric Wei-Guang
We report a method of detachment and transfer of one-dimensional TiO2 nanotube (NT) arrays to fabricate dye-sensitized solar cells (DSSCs) with illumination from the front side. The ordered NT arrays (tube length 20 mm) were detached from the NT-Ti substrate, as annealed, by means of a second anodization at 20 V for 4 h and then transferred, inverted, onto a transparent substrate of conducting oxide (TCO) with an interface of TiO2 nanoparticles of thickness similar to 2 mu m. Dry etching of the NT surface in a highly dense plasma reactor under BCl3/Cl-2 for 90 s opened previously closed ends of the tubes. The inverted (bottom-up) NT-TCO substrate was fabricated into a DSSC device that shows a cell performance (eta = 6.24%) significantly improved over those of a front-illuminated counterpart with an upright (face-up) structure (eta = 4.84%) and of a conventional back-illuminated device (eta = 4.61%). Electrochemical impedance spectra (EIS) of the devices under one-sun irradiation were measured to rationalize the cell performances that are consistent with the corresponding interfacial impedances between the NT arrays and the electrode for collection of electrons.
Effects of aggregation and electron injection on photovoltaic performance of porphyrin-based solar cells with oligo(phenylethynyl) links inside TiO(2) and Al(2)O(3) nanotube arrays
(2010-01-01)
Luo, Liyang
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Lin, Chia-Jung
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Tsai, Chiau-Yiag
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Wu, Hui-Ping
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Li, Lu-Lin
Porphyrins with phenylethynyl links of varied length (PE1-PE4) were sensitized on vertically oriented, anodic titanium-oxide (ATO) nanotube arrays for application as dye-sensitized solar cells (DSSC). The efficiency of power conversion decreased systematically from the dye with a short link to the dye with a long link. We measured the efficiency of conversion of incident photons to current (IPCE), the photocurrent decay of the devices, and steady-state and time-resolved fluorescence spectra of the thin-film samples to understand how the cell performance depends on the length of the link. Measurements of femtosecond fluorescence confirmed that the efficiency of electron injection depended on length because of dye aggregation that significantly increased the rate of aggregate-induced energy transfer for porphyrins with a long link. The rate of electron injection depended on the length of the link with an attenuation factor beta similar to 0.1 angstrom(-1). Resonant energy transfer (RET) kinetics of porphyrins sensitized on anodic aluminium-oxide (AAO) nanotube arrays were performed with picosecond time-correlated single-photon counting and four molecular densities for each porphyrin. The kinetic data of PE1 and PE2 are described satisfactorily according to a Forster model, whereas those of PE3 and PE4 conform to a Dexter formula. A formation of clusters is proposed to rationalize the observed density-dependent kinetics for the RET of porphyrins on semiconductor films.
Effects of aggregation and electron injection on photovoltaic performance of porphyrin-based solar cells with oligo(phenylethynyl) links inside TiO2 and Al2O3 nanotube arrays
(2010-01-01)
Luo, Liyang
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Lin, Chia-Jung
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Tsai, Chiau-Yiag
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Wu, Hui-Ping
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Li, Lu-Lin
Porphyrins with phenylethynyl links of varied length (PE1-PE4) were sensitized on vertically oriented, anodic titanium-oxide (ATO) nanotube arrays for application as dye-sensitized solar cells (DSSC). The efficiency of power conversion decreased systematically from the dye with a short link to the dye with a long link. We measured the efficiency of conversion of incident photons to current (IPCE), the photocurrent decay of the devices, and steady-state and time-resolved fluorescence spectra of the thin-film samples to understand how the cell performance depends on the length of the link. Measurements of femtosecond fluorescence confirmed that the efficiency of electron injection depended on length because of dye aggregation that significantly increased the rate of aggregate-induced energy transfer for porphyrins with a long link. The rate of electron injection depended on the length of the link with an attenuation factor beta similar to 0.1 angstrom(-1). Resonant energy transfer (RET) kinetics of porphyrins sensitized on anodic aluminium-oxide (AAO) nanotube arrays were performed with picosecond time-correlated single-photon counting and four molecular densities for each porphyrin. The kinetic data of PE1 and PE2 are described satisfactorily according to a Forster model, whereas those of PE3 and PE4 conform to a Dexter formula. A formation of clusters is proposed to rationalize the observed density-dependent kinetics for the RET of porphyrins on semiconductor films.
Enhanced photovoltaic performance with co-sensitization of porphyrin and an organic dye in dye-sensitized solar cells
(2012-04-01)
Lan, Chi-Ming
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Wu, Hui-Ping
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Pan, Tsung-Yu
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Chang, Chia-Wei
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Chao, Wei-Shan
We designed a stepwise approach for co-sensitization of a zinc porphyrin sensitizer (LD12) with a spirally configured organic dye (CD5) for dye-sensitized solar cells. The co-sensitized LD12 + CD5 device showed significantly enhanced V-OC and J(SC) relative to its individual single-dye sensitized devices. Upon optimization, the device made of the LD12 + CD5 system yielded J(SC)/mA cm(-2) = 16.7, V-OC/V = 0.74, FF = 0.73 and eta = 9.0%; this performance is superior to that of either individual device made from LD12 (eta = 7.5%) and CD5 (eta = 5.7%) under the same conditions of fabrication. To understand the effects of the potential shift and charge recombination on the cell performance, we measured charge-extraction (CE) and intensity-modulated photovoltage spectra (IMVS). Upon sensitization with each dye, the TiO2 potentials are similar, but co-sensitization causes the potential to shift down (cathodic shift). Charge recombination was significantly retarded for the co-sensitized system relative to each individual dye-sensitized system, to account for the enhanced V-OC for the former relative to the latter. A test of stability indicates a systematic trend between the LD12 + CD5 and LD12 devices; the performance of the co-sensitized device degraded only similar to 15% and remained stable during the period of 500-1000 h near 295 K.
Fabrication of long TiO(2) nanotube arrays in a short time using a hybrid anodic method for highly efficient dye-sensitized solar cells
(2010-01-01)
Li, Lu-Lin
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Tsai, Chiau-Yiag
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Wu, Hui-Ping
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Chen, Chien-Chon
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Diau, Eric Wei-Guang
We report a simple hybrid anodic method, with initial potentiostatic anodization followed by galvanostatic anodization, to grow much longer titania nanotube ( TNT) arrays in a much shorter anodization period (t). The length of the TNT arrays ( L) depends linearly on t and is controlled by the electric current; the growth rates are 5.3, 10.7 and 20.3 mu m h(-1) for current densities 3.7, 5.6 and 7.5 mA cm(-2), respectively. The produced TNT films of L = 15-57 mu m sensitized with N719 dye were fabricated into devices for photovoltaic characterization. The NT-DSSC devices show systematically improved cell performance depending on L, reflecting the excellent intrinsic light-scattering property of the NT-DSSC devices to harvest increased sunlight with long TNT arrays. The great effective surface area inside TNT arrays has been shown to significantly increase the dye loading, which might help to enhance the cell performance of the device with co-sensitizing of different dyes for improved efficiency of light harvesting in the future. The best performance of the NT-DSSC device was achieved at L similar to 30 mm with a spacer of similar thickness, giving J(SC) = 14.63 mA cm(-2), V(OC) = 0.741 V, FF = 0.70, and eta = 7.6%, which is unprecedented for a back-illumination DSSC.
Fabrication of long TiO2 nanotube arrays in a short time using a hybrid anodic method for highly efficient dye-sensitized solar cells
(2010-01-01)
Li, Lu-Lin
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Tsai, Chiau-Yiag
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Wu, Hui-Ping
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Chen, Chien-Chon
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Diau, Eric Wei-Guang
We report a simple hybrid anodic method, with initial potentiostatic anodization followed by galvanostatic anodization, to grow much longer titania nanotube ( TNT) arrays in a much shorter anodization period (t). The length of the TNT arrays ( L) depends linearly on t and is controlled by the electric current; the growth rates are 5.3, 10.7 and 20.3 mu m h(-1) for current densities 3.7, 5.6 and 7.5 mA cm(-2), respectively. The produced TNT films of L = 15-57 mu m sensitized with N719 dye were fabricated into devices for photovoltaic characterization. The NT-DSSC devices show systematically improved cell performance depending on L, reflecting the excellent intrinsic light-scattering property of the NT-DSSC devices to harvest increased sunlight with long TNT arrays. The great effective surface area inside TNT arrays has been shown to significantly increase the dye loading, which might help to enhance the cell performance of the device with co-sensitizing of different dyes for improved efficiency of light harvesting in the future. The best performance of the NT-DSSC device was achieved at L similar to 30 mm with a spacer of similar thickness, giving J(SC) = 14.63 mA cm(-2), V-OC = 0.741 V, FF = 0.70, and eta = 7.6%, which is unprecedented for a back-illumination DSSC.
High-Performance and Stable Gel-State Dye-Sensitized Solar Cells Using Anodic TiO2 Nanotube Arrays and Polymer-Based Gel Electrolytes
(2015-06-17)
Seidalilir, Zahra
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Malekfar, Rasoul
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Wu, Hui-Ping
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Shiu, Jia-Wei
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Diau, Eric Wei-Guang
Highly ordered and vertically oriented TiO2 nanotube (NT) arrays were synthesized with potentiostatic anodization of Ti foil and applied to fabricate gel-state dye-sensitized solar cells (DSSCs). The open structure of the TiO2 NT facilitates the infiltration of the gel-state electrolyte; their one-dimensional structural feature provides effective charge transport. TiO2 NTs of length L = 15-35 mu m were produced on anodization for periods of t = 5-15 h at a constant voltage of 60 V, and sensitized with N719 for photovoltaic characterization. A commercially available copolymer, poly(methyl methacrylate-co-ethyl acrylate) (PMMA-EA) served as a gelling agent to prepare a polymer-gel electrolyte (PGE) for DSSC applications. The PGE as prepared exhibited a maximum conductivity of 4.58 mS cm(-1) with PMMA-EA (7 wt %). The phase transition temperature (T-p) of the PGE containing PMMA-EA at varied concentrations was determined on the basis of the viscosities measured at varied temperatures. T-p increased with increasing concentration of PMMA-EA. An NT-DSSC with L = 30 mu m assembled using a PGE containing PMMA-EA (7 wt %) exhibited an overall power conversion efficiency (PCE) of 6.9%, which is comparable with that of a corresponding liquid-type device, PCE = 7.1%. Moreover, the gel-state NT-DSSC exhibited excellent thermal and light-soaking enduring stability: the best device retained similar to 90% of its initial efficiency after 1000 h under 1 sun of illumination at 50 degrees C, whereas its liquid-state counterpart decayed appreciably after light soaking for 500 h.
High-Performance Gel-Type Dye-Sensitized Solar Cells Using Poly (methyl methacrylate-co-ethylacrylate)-Based Polymer Gel Electrolyte with Superior Enduring Stability
(2015-01-01)
Seidalilir, Zahra
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Malekfar, Rasoul
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Shiu, Jia-Wei
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Wu, Hui-Ping
;
Diau, Eric Wei-Guang
We fabricated high-performance gel-state dye-sensitized solar cells (DSSCs) using TiO2 nanoparticles (NPs) and one-dimensional TiO2 nanotube (NT) arrays as electrodes and a polymer gel electrolyte (PGE), poly(methyl methacrylate-co-ethyl acrylate) (PMMA-EA), as a gelator in 3-methoxypropionitrile (MPN). MPN instead of acetonitrile (ACN) was used as a solvent to prepare PGE to overcome the drawback of high volatility of ACN so as to improve the long-term stability of the devices. The viscosities of the PGEs containing varied concentrations of PMMA-EA copolymer (4-13 wt%) were measured to obtain the gel to liquid phase transition temperature (T-p) of the PGEs. T-p systematically increased with increasing concentration of PMMA-EA. We found that the as prepared PGE showed the best electrical conductivity of 1.6 mS cm(-1) at 10 wt% of PMMA-EA, which is comparable with the value of the liquid electrolyte (1.7 mS cm(-1)). By employing 10 wt% of PMMA-EA as POE in MPN, the gel-type NT and NP-based devices exhibited power conversion efficiencies (PCE) 6.3 and 8.4%, respectively, which are comparable to those of the corresponding liquid-type counterparts, PCE = 6.4 and 9.1%, respectively. In addition, the enduring stability of MPN-based gel-state device was found to retain a high device efficiency for a long period under thermal and light-soaking dual stress. (C) 2015 The Electrochemical Society. All rights reserved.
High-Performance Large-Scale Flexible Dye-Sensitized Solar Cells Based on Anodic TiO2 Nanotube Arrays
(2013-10-01)
Jen, Hsiu-Ping
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Lin, Meng-Hung
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Li, Lu-Lin
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Wu, Hui-Ping
;
Huang, Wei-Kai
A simple strategy to fabricate flexible dye-sensitized solar cells involves the use of photoanodes based on TiO2 nanotube (TNT) arrays with rear illumination. The TNT films (tube length similar to 35 mu m) were produced via anodization, and sensitized with N719 dye for photovoltaic characterization. Pt counter electrodes of two types were used: a conventional FTO/glass substrate for a device of rigid type and an ITO/PEN substrate for a device of flexible type. These DSSC devices were fabricated into either a single-cell structure (active area 3.6 X 0.5 cm(2)) or a parallel module containing three single cells (total active area 5.4 cm(2)). The flexible devices exhibit remarkable performance with efficiencies eta = 5.40 % (single cell) and 4.77 % (parallel module) of power conversion, which outperformed their rigid counterparts with eta = 4.87 % (single cell) and 4.50 % (parallel model) under standard one-sun irradiation. The flexible device had a greater efficiency of conversion of incident photons to current and a broader spectral range than the rigid device; a thinner electrolyte layer for the flexible device than for the rigid device is a key factor to improve the light-harvesting ability for the TNT-DSSC device with rear illumination. Measurements of electrochemical impedance spectra show excellent catalytic activity and superior diffusion characteristics for the flexible device. This technique thus provides a new option to construct flexible photovoltaic devices with large-scale, light-weight, and cost-effective advantages for imminent applications in consumer electronics.
Highly efficient porphyrin-sensitized solar cells with enhanced light harvesting ability beyond 800 nm and efficiency exceeding 10%
(2014-04-01)
Wang, Chin-Li
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Hu, Jyun-Yu
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Wu, Cheng-Hua
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Kuo, Hshin-Hui
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Chang, Yu-Cheng
A new porphyrin sensitizer, LD31, was designed based on a donorp- pi-acceptor structure, in which an ethynyl-anthracenyl moiety was inserted between the dioctylaminophenyl group and the porphyrin core in order to extend the p-conjugation of the dye for improved light-harvesting ability. The device made of LD31 exhibited panchromatic spectral features covering the whole visible region and further extending over 800 nm. When combined with an organic dye (AN-4), the performance of the LD31/AN-4 co-sensitized device attained JSC/ mA cm(-2) = 20.3, VOC/mV = 704, FF = 0.72, and the overall efficiency of power conversion eta=10.3%.
Hybrid Titania Photoanodes with a Nanostructured Multi-Layer Configuration for Highly Efficient Dye-Sensitized Solar Cells
(2013-05-02)
Wu, Hui-Ping
;
Lan, Chi-Ming
;
Hu, Jyun-Yu
;
Huang, Wei-Kai
;
Shiu, Jia-Wei
To construct a hybrid titania photoanode containing nanoparticles and nanorods of varied size in a multilayer (ML) configuration for dye-sensitized solar cells, the essence of our ML design is a bilayer system with additional layers of nanorods of well-controlled size inserted between the transparent and the scattering layers to enhance the light harvesting capability for photosensitizers with small absorptivity, such as Z907. We measured charge-extraction and intensity-modulated photoelectric spectra to show the advantages of one-dimensional nanorods with an improved electron-transport property and an upward shift of the potential band edge; a favorable ML configuration was constructed to have a cascade potential feature for feasible electron transport from long nanorods, to normal nanorods, to small nanoparticles. On the basis of the ML system reported herein, we demonstrate how the performance of a Z907 device is improved to attain eta similar to 10%, which is a milestone for its future commercialization.