Browsing by Author "Dinelli, Franco"

Now showing 1 - 2 of 2

Influences of thermal annealing on P3HT/PCBM interfacial properties and charge dynamics in polymer solar cells
(2015-12-01)
Cheng, Cheng-En
;
Dinelli, Franco
;
Yu, Chen-Te
;
Shih, Hwa-Wei
;
Pei, Zingway
The effects of thermal annealing on the interfacial properties of poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl C-61 butyric acid methyl ester (PCBM) and on the charge dynamics in P3HT: PCBM polymer solar cells (PSCs) are investigated. This study determines that an effective phase separation of the P3HT and PCBM caused by thermal annealing achieves a larger interfacial area for efficient exciton dissociation and a well-defined pn junction with few defect levels at the P3HT/PCBM interface. Additionally, thermal annealing creates a compositional gradient across the P3HT: PCBM films, which enhances the charge transit ability significantly. These improved interfacial properties and efficiency in charge transit ability account for the better power conversion efficiency of P3HT: PCBM PSCs treated with thermal annealing. (C) 2015 The Japan Society of Applied Physics
Revealing the flexoelectricity in the mixed-phase regions of epitaxial BiFeO3 thin films
(2015-01-28)
Cheng, Cheng-En
;
Liu, Heng-Jui
;
Dinelli, Franco
;
Chen, Yi-Chun
;
Chang, Chen-Shiung
Understanding the elastic response on the nanoscale phase boundaries of multiferroics is an essential issue in order to explain their exotic behaviour. Mixed-phase BiFeO3 films, epitaxially grown on LaAlO3 (001) substrates, have been investigated by means of scanning probe microscopy to characterize the elastic and piezoelectric responses in the mixed-phase region of rhombohedral-like monoclinic (M-I) and tilted tetragonal-like monoclinic (M-II,M-tilt) phases. Ultrasonic force microscopy reveal that the regions with low/ high stiffness values topologically coincide with the M-I/M-II,M-tilt phases. X-ray diffraction strain analysis confirms that the M-I phase is more compliant than the M-II,(tilt) one. Significantly, the correlation between elastic modulation and piezoresponse across the mixed-phase regions manifests that the flexoelectric effect results in the enhancement of the piezoresponse at the phase boundaries and in the M-I regions. This accounts for the giant electromechanical effect in strained mixed-phase BiFeO3 films.