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Lee Y.-I.,KAIST | Lee Y.-I.,Advanced Display Research Center | Youn J.-H.,KAIST | Youn J.-H.,Advanced Display Research Center | And 4 more authors.
Journal of Applied Physics | Year: 2010

We have studied the modification of electrical properties in poly(3-hexylthiophene) (P3HT) thin film by means of illumination and annealing. The hole mobility of P3HT was monitored by impedance spectroscopy and the density of localized states in the band gap near the Fermi level was calculated using the step-by-step method based on the space-charge-limited-current model. With the illumination, we found that the bulk trap density increased from 2.51 to 2.85× 1016 cm-3 eV-1 and the hole mobility of P3HT decreased from 1.88× 10-4 cm2 V-1 s-1 to 4.22× 10-5 cm2 V-1 s-1. With the annealing at 70 °C for 30 min, it is found that the mobility then partially recovers to 1.18× 10-4 cm2 V-1 s-1. © 2010 American Institute of Physics.


Lee Y.-I.,KAIST | Lee Y.-I.,Advanced Display Research Center | Youn J.-H.,KAIST | Youn J.-H.,Advanced Display Research Center | And 4 more authors.
Japanese Journal of Applied Physics | Year: 2011

We have studied the degradation of poly(3-hexylthiophene):methano-fullerene [6,6]-phenyl-C71 butyric acid methyl ester (P3HT:PC71BM) bulk heterojunction BHJ solar cells and the annealing effect on the degraded devices. Firstly, the modification of electrical properties of the BHJ solar cells was monitored as a function of illumination time. The degradation of BHJ solar cell is dominated by the filling factor reduction and an irradiation to the solar cell accelerates the gradual degradation. Secondly, we found that inserting LiF between Al cathode and active layer, alleviating degradation, improves the device properties of the solar cell as well as its stability. Moreover, annealing on the degraded device helps partially recover the properties of the solar cell and the diode function. We speculated that this partial recovery caused by annealing is attributed to the rearrangement of P3HT as well as the aggregation of PC71BM. © 2011 The Japan Society of Applied Physics.

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