Browsing by Author "Chiang, Chien-Hung"

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A novel ball milling technique for room temperature processing of TiO2 nanoparticles employed as the electron transport layer in perovskite solar cells and modules
(2018-04-28)
Singh, Mriganka
;
Chiang, Chien-Hung
;
Boopathi, Karunakara Moorthy
;
Hanmandlu, Chintam
;
Li, Gang
Anatase titanium dioxide (an-TiO2) is often used as the electron transporting material (ETM) in planar-heterojunction perovskite solar cells (PSCs) because of its excellent semiconductor characteristics, outstanding optical transmittance, and suitable band structure. Herein, we report an inexpensive method for mass-scale production of TiO2 ETMs at room temperature (RT similar to 30 degrees C), involving the grinding of large clumps of an-TiO2 to form a suspension of TiO2 nanoparticles (NPs) in isopropyl alcohol for meso-superstructured PSCs. This process does not involve any chemical synthesis; it is a purely physical process. The lowest unoccupied molecular orbital (LUMO) of ground an-TiO2 NPs, estimated using ultraviolet photoelectron spectroscopy (UPS), was ca. 4.06 eV, which is a salient feature for the active layer. A regular perovskite solar cell (PSC) based on a CH3NH3PbI3 absorber and ground an-TiO2 ETL exhibited a champion power conversion efficiency (PCE) of 17.43% with an active area of 0.1 cm(2). The same ground an-TiO2 NPs were used to fabricate a large-area (designated area: 25.2 cm(2)) PSC and a PCE of 14.19% was achieved. PSC devices incorporating the ground an-TiO2 NP ETLs exhibited an attractive long-term device stability, with the PCE retaining approximately 85% of the initial values after 80 days.
Influence of Postdeposition Annealing on Physical and Electrical Properties of High-k Yb2TiO5 Gate Dielectrics
(2010)
Pan, Tung-Ming
;
Yen, Li-Chen
;
Chiang, Chien-Hung
;
Chao, Tien-Sheng
;
電子物理學系
The structure and electrical properties of a high-k Yb2TiO5 gate dielectric deposited on Si(100) substrates through reactive cosputtering were investigated. X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy were used to study the morphological and chemical features of these films as functions of the growth conditions. The Yb2TiO5 dielectrics annealed at 800 degrees C exhibited a thinner capacitance equivalent thickness, a lower gate leakage current, a smaller density of interface state, and a relatively lower hysteresis voltage compared to those at other annealing temperatures. These results are attributed to the formation of a rather well-crystallized Yb2TiO5 structure and composition.