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    Effect of trichlorobenzene additive on the performance and morphology of polyfluorene and fullerene derivative bulk heterojunction solar cells
    (2012-08-01)
    Koetniyom, W.
    ;
    Keawprajak, A.
    ;
    Piyakulawat, P.
    ;
    Jiramitmongkon, K.
    ;
    Nukeaw, J.
    The influence of additive, namely 1,3,5-trichlorobenzene (TCB), on the morphology and performance of bulk heterojunction (BHJ) organic solar cells was studied based on a 1:2 (w/w) blend of benzothiadiazole/thiophene-based copolymers (PFTBzTT) to [6,6]-phenyl-C <inf>61</inf> butyric acid methyl ester (PCBM). The active layers were deposited by spin-coating from solutions using chloroform, with different additive concentrations from 0 to 36mg/ml. The addition of solvent additive into the polymer solution was able to improve the performance of BHJ solar cells. The maximum power conversion efficiency (%PCE) of 0.85% was obtained for a cell with the TCB concentration of 12mg/ml after annealing at 180°C for 20min. From atomic force microscopy (AFM) images, the films processed without TCB appear smoother than those with the TCB additive. A large extent of segregation was also observed in the films processed with a high TCB concentration. The optical images of the thin films suggest that the optimum concentrations of the additive cause the polymer self-organisation, resulting in some aggregation of large PCBM crystals. © 2011 Canadian Society for Chemical Engineering.
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    Electroreflectance and photocurrent measurement of ZnSe/Alq 3/TPD heterostructure on Si-substrate
    (2005-11-20)
    Pecharapa, W.
    ;
    Keawprajak, A.
    ;
    Kayunkid, N.
    ;
    Rahong, S.
    ;
    Yindeesuk, W.
    The optical transition energy in ZnSe/tris(8-hydroxyquinoline) aluminum (Alq<inf>3</inf>)/N,N′-bis(3-methylphenyl)-N,N′-diphenyl-benzidine (TPD) heterostructure were investigated by room-temperature electroreflectance (ER) and photocurrent (PC) measurements. PC signal showed wavelength response of the device in the range of 450-1100 nm. ER features due to optical transition energy of the single quantum well of this structure were observed. The transition energies were determined by fitting the ER spectra to the theoretical line-shape expression. The subband transition energy decreased with increasing well thickness. Under applied voltage, both ER signals show significant shift due to the quantum confined Stark effect. © 2005 Elsevier B.V. All rights reserved.