Browsing by Author "Wei, Hung-Yu"

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A counter electrode based on hollow spherical particles of polyaniline for a dye-sensitized solar cell
(2012)
Huang, Kuan-Chieh
;
Hu, Chih-Wei
;
Tseng, Chen-Ya
;
Liu, Chen-Yu
;
Yeh, Min-Hsin
Hollow spherical polyaniline (hsPANI) particles are synthesized and deposited on an ITO/glass substrate to prepare a counter electrode (designated as hsPANI-CE) for a dye-sensitized solar cell (DSSC). The structure and crystallization of the hsPANI particles are characterized by using high resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectra. A power-conversion efficiency (h) of 6.84% is obtained for the DSSC with the hsPANI-CE, while it is 6.02% in the case of the DSSC with a CE based on pristine PANI (designated as PANI-CE). Such enhancement is attributed to the hsPANI film having a larger active surface area (A) of 0.191 cm(2), compared to that of the PANI film (A = 0.126 cm(2)), both values being estimated by a rotating disk electrode (RDE). Cyclic voltammetric (CV) curves have evidenced that the electro-catalytic ability of the hsPANI-CE for the reduction of tri-iodide (I-3(-)) ions is higher than that of the PANI-CE. As a reference, the DSSC with a Pt-sputtered CE gives an h of 7.17%. Electrochemical impedance spectroscopic (EIS) spectra are used to substantiate the photovoltaic behaviors. The results suggest that the film consisting of hsPANI particles can be a potential catalytic layer for the replacement of Pt in the CE of a DSSC.
A dual-functional additive improves the performance of molecular bulk heterojunction photovoltaic cells
(2014)
Farahat, Mahmoud E.
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Wei, Hung-Yu
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Ibrahem, Mohammed Aziz
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Boopathi, Karunakara Moorthy
;
Wei, Kung-Hwa
In this paper we report a simple and effective approach towards improving the performance of molecular bulk heterojunction (BHJ) photovoltaics through incorporation of a new, nonvolatile processing additive; (3-chloropropyl) trimethoxysilane (CP3MS). A small amount of the additive CP3MS combined with post-annealing treatment significantly enhanced the power conversion efficiency (PCE) of dialkylated diketopyrrolopyrrole chromophore (SMDPPEH)-based molecular BHJ solar cells. The PCE increased from 2.75% for a device prepared without the additive or annealing to 4.55% for a device containing 0.1% CP3MS that had been subjected to post-annealing treatment at 100 degrees C for 10 min. CP3MS performed an interesting dual function when incorporated as an additive in molecular BHJ devices. The first was that it controlled the morphology: the addition of 0.1% CP3MS to the SMDPPEH: PC61BM blend was sufficient to improve the film's crystallinity and morphology. The second function was the spontaneous migration of the CP3MS molecules from the bulk to the interface between the active layer and the Al cathode, forming an ultrathin interlayer that acted as a buffer layer suppressing charge recombination and enhancing charge transport at the interface. Analyses using atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, together with examinations of device performance, confirmed the dual-functional nature of CP3MS as an additive. CP3MS also showed its promising ability to enhance the performance of different blend systems. The performance of benzodithiophene (BDT)-based molecular solar cells enhanced from 3.05% without additive to 3.8% with the incorporation of 0.1% CP3MS.
A high performance electrochemical sensor for acetaminophen based on a rGO-PEDOT nanotube composite modified electrode
(2014)
Huang, Tzu-Yen
;
Kung, Chung-Wei
;
Wei, Hung-Yu
;
Boopathi, Karunakara Moorthy
;
Chu, Chih-Wei
In this study, we perform an electrochemical sensing using a conductive composite film containing reduced graphene oxide (rGO) and poly(3,4-ethylenedioxythiophene) nanotubes (PEDOT NTs) as an electrode modifier on a glassy carbon electrode (GCE). Scanning electron microscopy suggests that the rGO covers the surface of GCE uniformly and the PEDOT NTs act as a conducting bridge to connect the isolated rGO sheets. By combining these two materials, the conductivity and the surface coverage of the film can be enhanced, which is beneficial for electrochemical sensing. The rGO-PEDOT NT composite modified electrode is applied for an effective sensor to analyze acetaminophen. The obtained electrochemical activity is much higher than those obtained by the rGO-and PEDOT NT-modified electrodes; the higher electrochemical activity may be attributed to the higher conductivity and greater coverage of the rGO-PEDOT NT composite film on the GCE. Furthermore, interference tests indicate that the rGO-PEDOT NT composite modified electrode exhibits high selectivity toward the analyte. This novel method for combining the rGO and PEDOT NTs establishes a new class of carbon material-based electrodes for electrochemical sensors.
A Strategic Buffer Layer of Polythiophene Enhances the Efficiency of Bulk Heterojunction Solar Cells
(2010-05-01)
Wei, Hung-Yu
;
Huang, Jen-Hsien
;
Ho, Kuo-Chuan
;
Chu, Chih-Wei
;
光電工程學系
We have developed polymer solar cells featuring a buffer layer of polythiophene (PT) sandwiched between the active layer and the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer. We attribute the improvement in power conversion efficiency of these polymer solar cells, relative to that of those based on poly(3-hexylthiophene):[6,6]-phenyl-C(61)-butyric acid methyl ester (P3HT:PCBM), to a reduction in the degree of carrier recombination at the junction interface. Because the conductivity and the energy level of PT can be tuned simply by applying a bias to it in an electrolytic solution, we also investigated the effect of the energy level on the devices' performances. The power conversion efficiency of a solar cell containing a PT buffer layer reached 4.18% under AM 1.5 G irradiation (100 mW/cm(2)).
Conducting polymer-based counter electrode for a quantum-dot-sensitized solar cell (QDSSC) with a polysulfide electrolyte
(2011-12-15)
Yeh, Min-Hsin
;
Lee, Chuan-Pei
;
Chou, Chen-Yu
;
Lin, Lu-Yin
;
Wei, Hung-Yu
Conducting polymer materials, i.e., polythiophene (PT), polypyrrole (PPy), and poly(3,4-ethylenedioxythiophene) (PEDOT) were used to prepare counter electrodes (CEs) for quantum-dot-sensitized solar cells (QDSSCs). The QDSSC with PEDOT-CE exhibited the highest solar-to-electricity conversion efficiency (eta) of 1.35%, which is remarkably higher than those of the cells with PT-CE (0.09%) and PPy-CE (0.41%) and very slightly higher than that of the cell with sputtered-gold-CE (1.33%). Electrochemical impedance spectra (EIS) show that this highest conversion efficiency of the PEDOT-based cell is due to higher electrocatalytic activity and reduced charge transfer resistance at the interface of the CE and the electrolyte, compared to those in the case of the cells with other conducting polymers and bare Au. Furthermore, the influences of morphology of the PEDOT film and the charge passed for its electropolymerization on the performance of its QDSSC were also studied. The higher porosity and surface roughness of the PEDOT matrix, with reference to those of other polymers are understood to be the reason for PEDOT to possess higher electrocatalytic activity at its interface with electrolyte. (C) 2011 Elsevier Ltd. All rights reserved.
Dual-color electrochromic films incorporating a periodic polymer nanostructure
(2012)
Wei, Hung-Yu
;
Hsiao, Yu-Sheng
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Huang, Jen-Hsien
;
Hsu, Chih-Yu
;
Chang, Feng-Chih
In this study, we used electrochemical deposition with a polystyrene (PS) bead template to prepare thin layers of poly(3,4-ethylenedioxythiophene) (PEDOT) that has a nanometer-scale honeycomb periodicity. To achieve dual-color electrochromic films, we then used pulsed electrochemical deposition to form polyaniline (PANI) layers on the rims of the PEDOT honeycomb film. Modifying the depositing charge density of PANI allowed tuning of the color of the composite films. We estimated the coloration efficiencies with respect to the values expected for corresponding amounts of pristine single layers of PEDOT and PANI. As a result of improved contact between the polymer film and the electrolyte, the coloration efficiencies of the structured composite films were much closer to their theoretical values than those of the corresponding bilayer composite films. Moreover, the switching times of the structured composite films were much faster than those of the bilayer composite films prepared without the nanostructures.
Effects of mesoscopic poly (3,4-ethylenedioxythiophene) films as counter electrodes for dye-sensitized solar cells
(2010-01-01)
Lee, Kun-Mu
;
Chiu, Wei-Hao
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Wei, Hung-Yu
;
Hu, Chih-Wei
;
Suryanarayanan, Vembu
Counter electrode coated with chemically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) in a dye-sensitized solar cell (DSSC) was studied. The surface morphology and the nature of I(-)/I(3)(-) redox reaction based on PEDOT film were investigated using Atomic Force Microscopy and Cyclic Voltammetry, respectively. The performance of the DSSCs containing the PEDOT coated electrode was compared with sputtered-Pt electrode. We found that the root mean square roughness decreases and conductivity increases as the molar ratio of imidazole (Im)/EDOT in the PEDOT film increases. The DSSC containing the PEDOT coated on fluorine doped tin oxide glass with Im/EDOT molar ratio of 2.0, showed a conversion efficiency of 7.44% compared to that with sputtered-Pt electrode (7.77%). The high photocurrents were attributed to the large effective Surface area of the electrode material resulting in good catalytic properties for T(3) reduction. Therefore, the incorporation of a multi-walled carbon nanotube (MWCNT) in the PEDOT film, coated on various substrates was also investigated. The DSSC containing the PEDOT films with 0.6 wt.% of MWCNT on stainless steel as counter electrode had the best cell performance of 8.08% with short-circuit current density, open-circuit voltage and fill factor of 17.00 mA cm(-2), 720 mV and 0.66, respectively. (C) 2009 Elsevier B.V. All rights reserved.
Efficient bulk heterojunction solar cells based on a low-bandgap polyfluorene copolymers and fullerene derivatives
(2009-09-01)
Huang, Jen-Hsien
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Li, Kuang-Chieh
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Wei, Hung-Yu
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Chen, Po-Yen
;
Lin, Lu-Yin
A low-bandgap polymer (PF-PThCVPTZ) consisted of fluorene and phenothiazine was designed and synthesized. With the donor-acceptor segment, the partial charge transfer can be built in the polymer backbone leading to a wide absorbance. The absorption spectrum of PF-PThCVPTZ exhibits a peak at 510 nm and an absorption onset at 645 nm in the visible range. As blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor, narrow bandgap PF-PThCVPTZ as electron donor shows significant solar cell performance. Under AM 1.5 G, 100 mA/cm(2) illumination, a power conversion efficiency (PCE) of 1.85% was recorded, with a short circuit current (J(SC)) of 5.37 mA/cm(2), an open circuit voltage (V(OC)) of 0.80 V, and a fill factor (FF) of 43.0%. (C) 2009 Elsevier B.V. All rights reserved.
Empowering Device-to-Device Networks with Cross-Link Interference Management
(2017-04)
Chiu, Shang-Lun
;
Lin, Kate Ching-Ju
;
Lin, Guang-Xun
;
Wei, Hung-Yu
;
資訊工程學系
Device-to-device (D2D) communications is an emerging service model that is currently under standardization by 3GPP. While D2D offloading has a great potential to relieve increasingly congested cellular networks, its benefits, however, come at a cost, namely interference. Most of the prevailing D2D designs conservatively avoid interference via either spectrum resource allocation or power control. These designs, however, do not exploit spatial degrees of freedom (DoF), which are inherently supported by multiantenna devices. In this work, we present MD2D, a multiuser D2D system that embraces concurrent D2D transmissions, while leveraging MIMO techniques to actively eliminate interference across D2D pairs. MD2D has a systematic methodology that checks whether the antenna combination in a D2D network is capable of eliminating cross-pair interference and, thereby, ensuring interference-free concurrent transmissions. If the interference can be eliminated, then MD2D applies a bucket-based DoF assignment algorithm to determine an effective antenna usage configuration that handles the interference. We evaluate our design via testbed experiments and large-scale simulations. The results show that, as compared to the traditional interference avoidance scheme, MD2D improves the throughput by 87.39 and 218.84 percent in a three-pair testbed and in large-scale simulations, respectively.
Highly conductive PEDOT:PSS electrode by simple film treatment with methanol for ITO-free polymer solar cells
(2012-11-01)
Alemu, Desalegn
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Wei, Hung-Yu
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Ho, Kuo-Chuan
;
Chu, Chih-Wei
;
光電工程學系
We proposed a simple yet robust film treatment method with methanol having only one hydroxyl group to enhance the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by four orders of magnitude. Different methods of film treatment: immersing PEDOT:PSS film in the methanol solution; dropping methanol on the film; and a combination of these are employed and the results are compared. The conductivity of PEDOT:PSS films was enhanced from 0.3 S cm(-1) to 1362 S cm(-1) after film treatment with methanol. Other alcohols like ethanol and propanol were also used to treat the PEDOT:PSS film and showed inferior conductivity enhancement compared to methanol. The conductivity enhancement was greatly affected by the hydrophilicity and dielectric constant of the alcohols used. The mechanism of conductivity enhancement was investigated through various characterization techniques including FTIR, XPS and AFM. Removal of the insulator PSS from the film, and morphology and conformational changes are the mechanisms for the conductivity enhancement. The treated films also showed high transmittance and low sheet resistance desirable for a standalone electrode. ITO-free polymer solar cells were fabricated using PEDOT:PSS electrodes treated with methanol and showed almost equal performance to ITO electrodes.
Inter-Client Interference Cancellation for Full-Duplex Networks
(2017-01-01)
Hsu, Kai-Cheng
;
Lin, Kate Ching-Ju
;
Wei, Hung-Yu
;
資訊工程學系
;
Department of Computer Science
Recent studies have experimentally shown the gains of full-duplex radios. However, due to its relatively higher cost and complexity, we can envision a more practical step in the network evolution is to have a full-duplex access point (AP) but keep the clients half-duplex. Unfortunately, the full-duplex gains can hardly be extracted in practice as the uplink transmission from a half-duplex client introduces inter-client interference to another downlink client. To address this issue, we present the design and implementation of IC2 (Inter-Client Interference Cancellation), the first physical layer solution that exploits the AP's full-duplex capability to actively cancel the interference at the downlink client. Such active cancellation not only improves the achievable capacity, but also better tolerates imperfect user pairing, simplifying the MAC design as a result. We build a prototype of IC2 on USRP-N200 and evaluate its performance via both testbed experiments and large-scale trace-driven simulations. The results show that, without IC2, about 60% of client pairs produce no gain from full-duplex transmissions, while, with IC2 the median throughput gain over conventional half-duplex networks can be 1.65x even when clients are simply paired randomly.
Inter-Client Interference Cancellation for Full-Duplex Networks With Half-Duplex Clients
(2019-10-01)
Lin, Kate Ching-Ju
;
Hsu, Kai-Cheng
;
Wei, Hung-Yu
;
資訊工程學系
;
Department of Computer Science
Recent studies have experimentally shown the gains of full-duplex radios. However, due to its relatively higher cost and complexity, we can envision a more practical step in the network evolution is to have a full-duplex access point (AP) but keep the clients half-duplex. Unfortunately, the full-duplex gains can hardly be extracted in practice as the uplink transmission from a half-duplex client introduces inter-client interference to another downlink client. To address this issue, we present the design and implementation of IC2 (Inter-Client Interference Cancellation), the first physical layer solution that exploits the AP's full-duplex capability to actively cancel the interference at the downlink client. Such active cancellation not only improves the achievable capacity, but also better tolerates imperfect user pairing, simplifying the MAC design as a result. We build a prototype of IC2 on USRP-N200 and evaluate its performance via both testbed experiments and large-scale trace-driven simulations. The results show that, without IC2, about 60% of client pairs produce no gain from full-duplex transmissions, while, with IC2 the median gain of the achievable rate over conventional half-duplex networks can be 1.65x and 1.47x for 1- and 2-antenna scenarios, respectively, even when clients are simply paired randomly.
Organic solar cells featuring nanobowl structures
(2013-04-01)
Wei, Hung-Yu
;
Huang, Jen-Hsien
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Hsu, Chih-Yu
;
Chang, Feng-Chih
;
Ho, Kuo-Chuan
Although organic solar cells having a bilayer configuration provide continuous conducting pathways for carrier transport to the requisite electrodes, their efficiencies have remained low because of the short exciton diffusion lengths of organic semiconductors. In this paper, we describe unique spatial organic solar cells featuring nanobowl array structures that capture more light and generate more power than planar organic solar cells. To construct bilayer solar cells, we used electrochemical deposition (with polystyrene beads as the template) to fabricate poly(3,4-ethylenedioxythiophene) nanobowl arrays, functioning as the hole extraction layer, on indium tin oxide substrates and then deposited copper phthalocyanine and a fullerene (C-60 or C-70) to function as the active layer, onto the nanobowl arrays. By implementing this spatial structure, we could control the active layer's thickness, such that it would be suitable for exciton dissociation, while maintaining a high absorption of incident light (by increasing the absorber volume without decreasing the area of the donor-acceptor interface, such that the light path in the active layer was increased) and ensuring high exciton dissociation efficiency (by enlarging the donor-acceptor interface). Relative to an equally thick planar control active layer the photocurrent generated by such bilayer solar cells increased by approximately 90%.
Pair Auction and Matching for Resource Allocation in Full-Duplex Cellular Systems
(2020-04-01)
Chao, Cheng-Chih
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Wang, Chih-Yu
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Lee, Chia-Han
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Wei, Hung-Yu
;
Chen, Wen-Tsuen
Full-duplex techniques improve spectral efficiency in cellular networks by allowing a transceiver to simultaneously transmit and receive data with the same radio resource. To minimize self-interference and inter-node interference due to the deployment of full-duplex radio, users have to feed back their measurements of interference to allow the base station to effectively allocate resources and form transmission pairs. Considering that the interference measurements are private information, users may not report the true values and may try to gain their own benefits. To solve this problem, we propose a strategy-proof resource allocation mechanism for full-duplex cellular networks. The proposed scheme, which is based on auction and matching theories, guarantees that users report true values of their channel quality and utilities, and therefore guarantees the correctness of feedback information and the efficiency of resource allocation. Moreover, the proposed matching-based mechanism is theoretically proved to be stable and Pareto efficient. Simulation results confirm that, compared to a centralized scheme with non-truthful information from users, the proposed scheme can achieve an 11% gain.
rGO/SWCNT composites as novel electrode materials for electrochemical biosensing
(2013-05-15)
Huang, Tzu-Yen
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Huang, Jen-Hsien
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Wei, Hung-Yu
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Ho, Kuo-Chuan
;
Chu, Chih-Wei
In this study we performed electrochemical sensing using conductive carbon composite films containing reduced graphene oxide (rGO) and single-walled carbon nanotubes (SWCNTs) as electrode modifiers on glassy carbon electrodes (GCEs). Raman spectroscopy, transmission electron microscopy, atomic force microscopy, and scanning electron microscopy all suggested that the rGO acted as a surfactant, covering and smoothing out the surface, and that the SWCNTs acted as a conducting bridge to connect the isolated rGO sheets, thereby (i) minimizing the barrier for charge transfer between the rGO sheets and (ii) increasing the conductivity of the film. We used the rGO/SWCNT-modified GCE as a sensor to analyze hydrogen peroxide (H2O2) and beta-nicotinamide adenine dinucleotide (NADH), obtaining substantial improvements in electrochemical reactivity and detection limits relative to those obtained from rGO- and SWCNT-modified electrodes, presumably because of the higher conductivity and greater coverage on the GCE, due to pi-pi interactions originating from the graphitic structures of the rGO and SWCNTs. The electrocatalysis response was measured by cyclic voltammetry and amperometric current-time (i-t) curve techniques. The linear concentration range of H2O2 and NADH detection at rGO/SWCNT-modified electrode is 0.5-5 M and 20-400 mu M. The sensitivity for H2O2 and NADH detection is 2732.4 and 204 mu A mM(-1) cm(-2), and the limit of detection is 1.3 and 0.078 mu M respectively. Furthermore, interference tests indicated that the carbon composite film exhibited high selectivity toward H2O2 and NADH. Using GO as a solubilizing agent for SWCNTs establishes a new class of carbon electrodes for electrochemical sensors. (C) 2012 Elsevier B.V. All rights reserved.
Solution-processed zinc oxide nanoparticles as interlayer materials for inverted organic solar cells
(2013-01-01)
Ibrahem, Mohammed Aziz
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Wei, Hung-Yu
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Tsai, Meng-Hung
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Ho, Kuo-Chuan
;
Shyue, Jing-Jong
This paper describes inverted bulk heterojunction organic solar cells featuring solution-processed zinc oxide nanoparticles (ZnO NPs) as an electron extraction layer, prepared at relatively low annealing temperatures (<= 150 degrees C). A solution of ZnO NPs (average size: 25 nm) was prepared using a wet grinding method. When the ZnO interlayer was present in the solar cell, the vertical phase separation of the active layers prepared with and without solvent annealing exhibited similar gradient concentrations and, therefore, similar photocurrent generation, both of which were superior to those of conventional devices incorporating a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) hole extraction layer. We attribute this vertical phase separation to the similar surface energies of the fullerene derivative and the ZnO interlayer. Under simulated air mass (AM) 1.5 G illumination at 100 mW cm(-2), the power conversion efficiency of the optimized device was approximately 4%. (C) 2012 Elsevier B.V. All rights reserved.
Synthesis and applications of novel low bandgap star-burst molecules containing a triphenylamine core and dialkylated diketopyrrolopyrrole arms for organic photovoltaics
(2012)
Sahu, Duryodhan
;
Tsai, Chia-Hua
;
Wei, Hung-Yu
;
Ho, Kuo-Chuan
;
Chang, Feng-Chih
In this study, we used facile synthetic routes to construct two well-defined starburst donor/acceptor conjugated small molecules with broad absorption features; in TPAKP-2 and TPAKP-3, triphenylamine (TPA) moieties served as electron donor core units and dialkylated diketopyrrolopyrrole (DKP) moieties with symmetrical thiophene units served as electron acceptors, in 1 : 2 and 1 : 3 ratios, respectively. Our investigation of the photophysical properties indicated that the absorption bands of TPAKP-2, and TPAKP-3 extended up to 793 nm, with low optical band gaps of 1.56 and 1.65 eV respectively. Under illumination with AM 1.5 white light (100 mW cm(-2)), we investigated the performance of bulk heterojunction (BHJ) photovoltaic devices incorporating an active layer of an electron-donor small molecule (TPAKP-2 or TPAKP-3) blended with an electron acceptor: [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) at various weight ratios. The photovoltaic device containing the donor TPAKP-3 and the acceptor PC(71)BMat a 1 : 3 weight ratio exhibited the best power conversion efficiency (1.81%), with an open circuit voltage of 0.66 V, a short circuit current density of 7.93 mA cm(-2), and a fill factor of 34.7%.
Using a low temperature crystallization process to prepare anatase TiO(2) buffer layers for air-stable inverted polymer solar cells
(2010-01-01)
Huang, Jen-Hsien
;
Wei, Hung-Yu
;
Huang, Kuan-Chieh
;
Chen, Cheng-Lun
;
Wang, Rui-Ren
In this study, we fabricated inverted polymer solar cells featuring titanium dioxide (TiO(2)) as the electron collection layer and vanadium (V) oxide (V(2)O(5)) as the hole collection layer. TiO(2) films (anatase phase) were prepared by combining electrochemical deposition with high-pressure crystallization. The low temperature process used to obtain the TiO(2) films minimized interdiffusion of Ti and In species between the TiO(2) and ITO films and maintained the conductivity of the indium tin oxide substrate. The inverted device reached a power conversion efficiency of 3.22% and exhibited much better stability under ambient conditions relative to that of the corresponding conventional device.
Using a low temperature crystallization process to prepare anatase TiO2 buffer layers for air-stable inverted polymer solar cells
(2010-01-01)
Huang, Jen-Hsien
;
Wei, Hung-Yu
;
Huang, Kuan-Chieh
;
Chen, Cheng-Lun
;
Wang, Rui-Ren
In this study, we fabricated inverted polymer solar cells featuring titanium dioxide (TiO2) as the electron collection layer and vanadium (V) oxide (V2O5) as the hole collection layer. TiO2 films (anatase phase) were prepared by combining electrochemical deposition with high-pressure crystallization. The low temperature process used to obtain the TiO2 films minimized interdiffusion of Ti and In species between the TiO2 and ITO films and maintained the conductivity of the indium tin oxide substrate. The inverted device reached a power conversion efficiency of 3.22% and exhibited much better stability under ambient conditions relative to that of the corresponding conventional device.
Wet-milled transition metal oxide nanoparticles as buffer layers for bulk heterojunction solar cells
(2012)
Huang, Jen-Hsien
;
Huang, Tzu-Yen
;
Wei, Hung-Yu
;
Ho, Kuo-Chuan
;
Chu, Chih-Wei
"In this study, we used high-energy grinding to prepare solutions of well-dispersed transition metal oxides (TMOs), allowing the fabrication of crystalline TMO films with high surface coverage through solution processing without post-annealing. Moreover, because this solution-based method did not require surfactants, it preserved the intrinsic electronic and optical properties of the TMOs. The resulting smooth, continuous, and highly transparent TMO films were readily integrated into organic solar cells. After incorporating MoO3 thin films into bulk heterojunction solar cells, we obtained devices delivering power conversion efficiencies of up to 3.68%, rivalling those of devices fabricated with commercial poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as the hole collection layer."