Towards reliable charge-mobility benchmark measurements for organic semiconductors

Charge carrier mobility is a figure of merit commonly used to rate organic semiconducting materials for their suitability in applications such as solid-state lighting or photovoltaics. Although large variations are found in published mobility values on identical materials, there is little open discussion in the literature of the reproducibility of these results. We address this with an interlaboratory study of mobility measurements performed on a set of organic semiconductors using the space-charge limited current method. We found mobility measured on nominally identical devices could vary by more than one order of magnitude, with the largest sources of variation being poor electrodes and film thickness variation. Moreover, we found that mobility values extracted from identical data by different scientists would typically vary by a factor of 3. We propose a protocol for analysis and reporting that was found to reduce this analysis variation to as little as 20%. We also present general guidelines for improving the reproducibility of benchmark mobility measurements.