Browsing by Author "Chen, Peter"

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Femtosecond Excitonic Relaxation Dynamics of Perovskite on Mesoporous Films of Al2O3 and NiO Nanoparticles
(2014-08-25)
Hsu, Hung-Yu
;
Wang, Chi-Yung
;
Fathi, Amir
;
Shiu, Jia-Wei
;
Chung, Chih-Chun
The excitonic relaxation dynamics of perovskite adsorbed on mesoporous thin films of Al2O3 and NiO upon excitation at 450 nm were investigated with femtosecond optical gating of photoluminescence (PL) via up-conversion. The temporal profiles of emission observed in spectral region 670-810 nm were described satisfactorily with a composite consecutive kinetic model and three transient components representing one hot and two cold excitonic relaxations. All observed relaxation dynamics depend on the emission wavelength, showing a systematic time-amplitude correlation for all three components. When the NiO film was employed, we observed an extent of relaxation proceeding through the non-emissive surface state larger than through the direct electronic relaxation channel, which quenches the PL intensity more effectively than on the Al2O3 film. We conclude that perovskite is an effective hole carrier in a p-type electrode for NiO-based perovskite solar cells showing great performance.
Observation of strain-induced phonon mode splitting in the tetragonal hybrid halide perovskite
(2017-11-01)
Ahn, Hyeyoung
;
Huang, Hsin
;
Hsieh, Meng-I
;
Li, Ming-Hsien
;
Chen, Peter
We report the structural and low-frequency vibrational properties of methylammonium lead-iodide (MAPbI(3)) perovskites studied by terahertz spectroscopy. The characteristic low-frequency mode splitting is observed in room-temperature tetragonal MAPbI(3) films grown on Si, and the frequencies of split modes are found to coincide with those of orthorhombic phases. The strain arising from the symmetry and lattice mismatch against the substrates is responsible for the local distortion of inorganic cages and results in the mode-splitting. The use of a mesoporous TiO2 interlayer effectively reduces the strain at the perovskite-substrate interface and induces larger grain growth and the improvement of structural ordering in the tetragonal MAPbI(3) films. (C) 2017 The Japan Society of Applied Physics
p-type Mesoscopic Nickel Oxide/Organometallic Perovskite Heterojunction Solar Cells
(2014-04-23)
Wang, Kuo-Chin
;
Jeng, Jun-Yuan
;
Shen, Po-Shen
;
Chang, Yu-Cheng
;
Diau, Eric Wei-Guang
In this article, we present a new paradigm for organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/[6,6]-phenyl C61-butyric acidmethyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics.
Performance Characterization of Dye-Sensitized Photovoltaics under Indoor Lighting
(2017-04-20)
Chen, Chia-Yuan
;
Jian, Zih-Hong
;
Huang, Shih-Han
;
Lee, Kun-Mu
;
Kao, Ming-Hsuan
Indoor utilization of emerging photovoltaics is promising; however, efficiency characterization under room lighting is challenging. We report the first round-robin interlaboratory study of performance measurement for dye-sensitized photovoltaics (cells and mini-modules) and one silicon solar cell under a fluorescent dim light. Among 15 research groups, the relative deviation in power conversion efficiency (PCE) of the samples reaches an unprecedented 152%. On the basis of the comprehensive results, the gap between photometry and radiometry measurements and the response of devices to the dim illumination are identified as critical obstacles to the correct PCE. Therefore, we use an illuminometer as a prime standard with a spectroradiometer to quantify the intensity of indoor lighting and adopt the reverse-biased current voltage (I-V) characteristics as an indicator to qualify the I-V sampling time for dye-sensitized photovoltaics. The recommendations can brighten the prospects of emerging photovoltaics for indoor applications.