Browsing by Author "Li, Pei-Jung"

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Highly Efficient and Stable Inverted Polymer Solar Cells Integrated with a Cross-Linked Fullerene Material as an Interlayer
(2010-04-07)
Hsieh, Chao-Hsiang
;
Cheng, Yen-Ju
;
Li, Pei-Jung
;
Chen, Chiu-Hsiang
;
Dubosc, Martin
A novel PCBM-based n-type material, [6,6]-phenyl-C(61)-butyric styryl dendron ester (PCBSD). functionalized with a dendron containing two styryl groups as thermal cross-linkers, has been rationally designed and easily synthesized. In situ cross-linking of PCBSD was carried out by heating at a low temperature of 160 degrees C for 30 min to generate a robust, adhesive, and solvent-resistant thin film. This cross-linked network enables a sequential active layer to be successfully deposited on top of this interlayer to overcome the problem of interfacial erosion and realize a multilayer inverted device by all-solution processing. An inverted solar cell device based on an ITO/ZnO/C-PCBSD/P3HT:PCBM/PEDOT:PSS/Ag configuration not only achieves enhanced device characteristics, with an impressive PCE of 4.4%, but also exhibits an exceptional device lifetime without encapsulation; it greatly outperforms a reference device (PCE = 3.5%) based on an ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag configuration without the interlayer. This C-PCBSD interlayer exerts multiple positive effects on both P3HT/C-PCBSD and PCBM/C-PCBSD localized heterojunctions at the interface of the active layer, including improved exciton dissociation efficiency, reduced charge recombination, decreased interface contact resistance, and induction of vertical phase separation to reduce the bulk resistance of the active layer as well as passivation of the local shunts at the ZnO interface. Moreover, this promising approach can be applied to another inverted solar cell, ITO/ZnO/C-PCBSD/PCPDTBT:PC(71)BM/PEDOT:PSS/Ag, using PCPDTBT as the p-type low-band-gap conjugated polymer to achieve an improved PCE of 3.4%. Incorporation of this cross-linked C(60) interlayer could become a standard procedure in the fabrication of highly efficient and stable multilayer inverted solar cells.
Morphological Stabilization by In Situ Polymerization of Fullerene Derivatives Leading to Efficient, Thermally Stable Organic Photovoltaics
(2011-05-10)
Cheng, Yen-Ju
;
Hsieh, Chao-Hsiang
;
Li, Pei-Jung
;
Hsu, Chain-Shu
;
應用化學系
The successful design and synthesis of two styryl-functionalized fullerene derivatives, [6,6]-phenyl-C(61) -butyric acid styryl dendron ester (PCBSD) and [6,6]-phenyl-C 61 -butyric acid styryl ester (PCBS) is presented. The polymerizable PCBS or PCBSD materials are incorporated into a poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) blend to form an active layer of ternary blend. The blending systems are fi rst thermally annealed at 110 C for 10 min to induce optimal morphology, followed by heating at 150 C for 10 min to trigger the in situ polymerization of styrene groups. Through chemical crosslinking of PCBSD, the initial morphology of the blend (P3HT:PCBM:PCBSD = 6:5:1 in weight) can be effectively fi xed and stably preserved. The device based on this blend shows extremely stable device characteristics, delivering an average power conversion effi ciency (PCE) of 3.7% during long-term thermal treatment. By molecular engineering to reduce the insulating portion, PCBS with higher C 60 content (71 wt%) possesses better electron-transport properties than PCBSD (58 wt%). Encouragingly, at a low doping concentration of PCBS in the blend (P3HT:PCBM:PCBS = 6:5:1 in weight), linear-polymerized PCBS can stabilize the morphology against thermal heating. This device exhibits more balanced charge mobility to achieve an average PCE of 3.8% over 25 h heating at 150 degrees C.