Direct determination of trap density function based on the photoinduced charge carrier extraction technique

作者：Tajima Hiroyuki^*; Suzuki Tomohiko; Kimata Motoi

来源：Organic Electronics, 2012, 13(11): 2272-2280.

DOI：10.1016/j.orgel.2012.07.017

• Trap
• CELIV
• Photovoltaic effect
• Geminate pair
• Solar cell

Photoinduced charge carrier extraction experiments using a linearly increasing voltage (photo-CELIV) are reported for an organic thin film device from 1.8 to 150 K. This device is composed of an active layer of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM). Photo-CELIV data for a zigzag shape voltage sweep provide critical evidence that the CELIV signal reflects the evacuation of charged carriers captured by traps under a high electric field. The data are analyzed using the Poole-Frenkel model. The trap density as a function of escape energy is obtained as rho(epsilon) = D exp{-(epsilon - epsilon(0))(2)/sigma(2)}, with D = 1.0 x 10(24) states m(-3) eV(-1), epsilon(0) = 0.087 eV, and sigma = 0.029 eV. The carrier drift mobility is estimated to be 2.3 x 10(-6) cm(2) V-1 s(-1) at 1.8 K. As inferred from the light intensity dependence of the photo-CELIV data, geminate pairs are proposed as the origin of traps. This study demonstrates that carrier evacuation from a Coulomb potential effectively plays an important role in the electrical conduction of organic thin films.

• 出版日期2012-11