Browsing by Author "Leonardus, Mario"

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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
;
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.
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
;
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.
;
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.