Measurement of Charge‐Density Dependence of Carrier Mobility in an Organic Semiconductor Blend

Here, a new methodology for analyzing the charge‐density dependence of carrier mobility in organic semiconductors, applicable to the low‐charge‐density regime (10 14 –10 17 cm −3 ) corresponding to the operation conditions of many organic optoelectronic devices, is reported. For the P3HT/PCBM blend photovoltaic devices studied herein, the hole mobility µ is found to depend on charge density n according to a power law µ(n) ∝ n δ , where δ = 0.35. This dependence is shown to be consistent with an energetic disorder model based upon an exponential tail of localized intra‐band states.