Browsing by Author "Chan, Chien-Yi"

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Construction of a photoanode with varied TiO2 nanostructures for a Z907-sensitized solar cell with efficiency exceeding 10%
(2014)
Shiu, Jia-Wei
;
Lan, Zih-Jian
;
Chan, Chien-Yi
;
Wu, Hui-Ping
;
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.
Panchromatic co-sensitization of porphyrin-sensitized solar cells to harvest near-infrared light beyond 900 nm
(2015-01-01)
Shiu, Jia-Wei
;
Chang, Yen-Cheng
;
Chan, Chien-Yi
;
Wu, Hui-Ping
;
Hsu, Hung-Yu
We designed a dimeric porphyrin dye (LDD1) based on an efficient push-pull zinc porphyrin (LD14) with extended pi-conjugation through coupling of two zinc porphine cores via an acetylene bridge at the meso position of the porphyrin to extend the absorption spectrum effectively into the near infrared region. The effect of dye aggregation among porphyrin molecules was significantly suppressed when the LDD1 and LD14 dyes were co-sensitized on a nanocrystalline TiO2 film in a dye-sensitized photovoltaic system. The light-harvesting ability of the device exhibits a panchromatic feature covering a broad spectral region from 400 nmto 900 nm, which results in a short-circuit current density of 21.3 mA cm(-2) and a power conversion efficiency of 10.4% in an iodine-based solar cell.
Solvent-extraction crystal growth for highly efficient carbon-based mesoscopic perovskite solar cells free of hole conductors
(2016)
Chan, Chien-Yi
;
Wang, Yingying
;
Wu, Guan-Wei
;
Diau, Eric Wei-Guang
;
應用化學系
We developed a simple drop-casting method via solvent extraction (SECG) to grow dense and uniform perovskite nanocrystals at room temperature for carbon-based mesoscopic solar cells free of an organic hole-transport layer. The CH3NH3PbI3/N-methyl-2-pyrrolidone (NMP) precursor solution (40%) was first dripped onto a substrate with film configuration TiO2/Al2O3/C and infiltrated at 70 degrees C for 10 min. The perovskite substrate was next immersed in a bath of diethyl ether at 25 degrees C for 30 min. Third, the solventextracted substrate was stored in a dry box (humidity 50%) at 25 degrees C for at least 100 h to complete the crystal growth. The device performance attained a power conversion efficiency (PCE) of 12.3%, which is significantly greater than that of DMF (6.3%) and NMP (8.3%) devices using traditional thermal annealing. The SECG device displayed a superior intrinsic enduring stability: the PCE exceeded 12% for 5000 h with a maximum value of 13.3% without light-soaking at 25 degrees C, but the performance degraded rapidly under one-sun irradiation without encapsulation. To understand the kinetics of charge transfer and defect relaxation for the devices under investigation, we recorded transient photoluminescence decays at an excitation wavelength of 635 nm and a probe wavelength of 770 nm.