Browsing by Author "Mane, Sandeep B."

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Effects of Core-modification on Porphyrin Sensitizers to the Efficiencies of Dye-sensitized Solar Cells
(2014-05-01)
Mane, Sandeep B.
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Luo, Liyang
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Chang, Gao-Fong
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Diau, Eric Wei-Guang
;
Hung, Chen-Hsiung
To study dye-sensitized solar cells (DSSCs) with core-modified porphyrins as the sensitizing dyes, three porphyrins with an ethynyl benzoic acid as an anchoring group are prepared. The properties of free-base regular porphyrin (N4), thiaporphyrin (N3S) and oxaporphyrin (N3O) were thoroughly studied by spectroscopic methods, DFT calculations, and photovoltaic measurements. Replacing one of the porphyrinic core nitrogen atoms by oxygen or sulfur considerably changes the absorption spectra. The Soret band of the N3O and N3S observed bathochromic shifts of 3-9 nm while the Q band reaches 700 nm to the near-infrared region. The overall conversion efficiencies of the DSSCs based on these porphyrins are in the order N4 (3.66%) >> N3S (0.22%) > N3O (0.01%). The time-correlated single photon counting observed short fluorescence lifetimes for N3O adsorbed both on TiO2 and Al2O3 which explicates the poor efficiency of DSSC using N3O as the photosensitizer.
Effects of Position and Electronic Nature of Substituents on Cobalt-Porphyrin-Catalyzed Hydrogen Evolution Reaction
(2017-11-13)
Beyene, Belete B.
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Mane, Sandeep B.
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Leonardus, Mario
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Hung, Chen-Hsiung
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Cobalt(II) porphyrins bearing ortho/para-amino and ortho-nitro groups at meso-phenyl rings have been prepared and employed for catalytic hydrogen generation. Electrochemical and catalytic studies show that position and electronic nature of the substituents strongly affect catalytic activity and overpotential of catalysis. Our study reveals that the complex with ortho-aminophenyl substituents on porphyrin core displays higher activity toward H-2 evolution with rate constant of 1.1 x 10(5) M-1 s(-1) at onset potential close to thermodynamic reduction potential of trifluoroacetic acid (TFA), and 89% efficiency. On the other hand, the reactions involving cobalt porphyrins with para-aminophenyl or ortho-nitrophenyl groups showed lower or no activity under the same experimental conditions, implying the significant role of pendant ortho-amino groups in accelerating the intramolecular proton transfer and the proton-hydride interactions to thermodynamically favor H-2 evolution.
Novel expanded porphyrin sensitized solar cells using boryl oxasmaragdyrin as the sensitizer
(2013)
Mane, Sandeep B.
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Hu, Jyun-Yu
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Chang, Yu-Cheng
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Luo, Liyang
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Diau, Eric Wei-Guang
Oxasmaragdyrin boron complexes were prepared and applied in DSSCs. The HOMO-LUMO energy gap analyses and theoretical calculations revealed that these expanded porphyrins are ideal sensitizers for DSSCs. A device containing oxasmaragdyrin-BF2 as the sensitizer achieves an energy conversion efficiency of 5.7%.
Oxasmaragdyrins as New and Efficient Hole-Transporting Materials for High-Performance Perovskite Solar Cells
(2017-09-20)
Mane, Sandeep B.
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Sutanto, Albertus Adrian
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Cheng, Chih-Fu
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Xie, Meng-Yu
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Chen, Chieh-I
The high performance of the perovskite solar cells (PSCs) cannot be achieved without a layer of efficient hole-transporting materials (HTMs) to retard the charge recombination and transport the photogenerated hole to the counterelectrode. Herein, we report the use of boryl oxasmaragdyrins (SM01, SM09, and SM13), a family of aromatic core-modified expanded porphyrins, as efficient hole-transporting materials (HTMs) for perovskite solar cells (PSCs). These oxasmaragdyrins demonstrated complementary absorption spectra in the low-energy region, good redox reversibility, good thermal stability, suitable energy levels with CH3NH3PbI3 perovskite, and high hole mobility. A remarkable power conversion efficiency of 16.5% (V-oc= 1.09 V, J(sc) = 20.9 mA cm(-2), fill factor (FF) = 72%) is achieved using SM09 on the optimized PSCs device employing a planar structure, which is close to that of the state-of-the-art hole-transporting materials (HTMs), spiro-OMeTAD of 18.2% (V-oc = 1.07 V, J(sc) = 22.9 mA cm(-2), FF = 74%). In contrast, a poor photovoltaic performance of PSCs using SM01 is observed due to the interactions of terminal carboxylic acid functional group with CH3NH3PbI3.
Solvent-assisted crystallization via a delayed-annealing approach for highly efficient hybrid mesoscopic/planar perovskite solar cells
(2017-12-01)
Sutanto, Albertus Adrian
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Lan, Shiang
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Cheng, Chih-Fu
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Mane, Sandeep B.
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Wu, Hui-Ping
The formation of a dense and uniform perovskite film with large grain is an important factor for getting excellent device performance. Here, we report an optimized solvent-assisted crystallization procedure followed by a delayed annealing for easy and reproducible fabrications of perovskite solar cells with a hybrid mesoscopic configuration. The working electrode contains a mesoporous TiO2 scaffold layer of 100 nm deposited on FTO substrate with a thin TiO2 blocking layer. The devices in this study were assembled using all commercially available materials without any extensive modification. Formation of uniform and pin-hole free perovskite nanocrystals with film thickness 200 nm on top of the scaffold layer was achieved via an optimized solvent assisted crystallization method. A much smoother perovskite layer was achieved with a delayed annealing for a certain period. The best performing device was obtained at the annealing delayed for 60 min, giving the power conversion efficiency 16.9% with an average value 15.4% obtained from 60 devices.
The cis-isomer performs better than the trans-isomer in porphyrin-sensitized solar cells: interfacial electron transport and charge recombination investigations
(2015-01-01)
Luo, Liyang
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Ambre, Ram B.
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Mane, Sandeep B.
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Diau, Eric Wei-Guang
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Hung, Chen-Hsiung
We report characterizations and device performance for dye-sensitized solar cells using cis- and trans-isomers of 2D-pi-2A zinc porphyrins with carboxyphenyl and thienyl groups in their meso-positions. Under identical experimental conditions with similar dye loadings, we observed overall power conversion efficiencies of 2.44% and 0.88% for devices made of cis-2S2A and trans-2S2A, respectively. This uneven performance among cis and trans isomers under the same experimental conditions can be rationalized with detailed investigations via spectroscopic, quantum chemical, and femtosecond fluorescence up-conversion investigations. Density functional theory (DFT) calculations show that a small amount of electron density is localized over carboxyphenyl groups in the LUMO of cis-2S2A, but there is no electron density populated on the carboxyphenyl groups in the LUMO of trans-2S2A. The femtosecond fluorescence decay measurements revealed that the excited-state lifetime of trans-2S2A on Al2O3 is half of that of cis-2S2A on Al2O3. Moreover, the dye-to-TiO2 electron injection time of trans-2S2A is 2.54 ps, which is shorter than that of cis-2S2A/TiO2 (2.95 ps). Electrochemical impedance spectra measured under one sun illumination also revealed that the charge recombination time of cis-2S2A is longer than that of trans-2S2A. This thorough understanding of isomeric effects on the performance of porphyrins will serve as a guideline for the design of future sensitizing dyes for solar cells.