Relationship between Mobilities from Time-of-Flight and Dark-Injection Space-Charge-Limited Current Measurements for Organic Semiconductors: A Monte Carlo Study

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• 作者：Haoyuan Li ; Lian Duan ; Deqiang Zhang ; Guifang Dong ; Juan Qiao ; Liduo Wang ; Yong Qiu
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：March 27, 2014
• 年：2014
• 卷：118
• 期：12
• 页码：6052-6058
• 全文大小：357K
• 年卷期：v.118,no.12(March 27, 2014)
• ISSN：1932-7455

文摘

The dark-injection space-charge-limited current (DI-SCLC) and the time-of-flight (TOF) measurements are both widely used methods to obtain the charge mobilities of organic materials. The current formula used to calculate the mobility in the DI-SCLC measurement is based on the relationship that the peak time equals 0.787 times the transit time in the TOF measurement. This conclusion, however, is reached by assuming a constant mobility and a negligible carrier diffusion, which is not valid for organic materials. Here, we perform Monte Carlo simulations of the multiparticle charge carrier movement in the TOF and DI-SCLC measurements. We found that the relationship between the peak time and the transit time depends on the disorder of the system. For organic semiconductors, the current formula used in the DI-SCLC measurement is only valid when the energetic disorder is small or when the temperature is high, and large deviation will occur otherwise, which is due to the enhanced charge transport induced by high carrier density and inhomogeneous electric field in the space-charge-limited case.