Experimental design for the determination of the injection barrier height at metal/organic interfaces using temperature dependent current-voltage measurements

Determination of the injection barrier height for holes or electrons at metal/organic interfaces is essential to understanding the device physics of organic electronics. Due to the disordered molecular packing of organic semiconductors, careful consideration is required in the design of both the device structure and the experimental measurement technique used to extract the barrier height. We report a methodology for extracting the injection barrier height at metal/organic interfaces from temperature dependent current-voltage measurements. This methodology includes the design of single carrier devices with specific consideration of the intrinsic properties of organic semiconductors, as well as the design of a variable temperature cryostat suited to the measurement of organic electronic device architectures. Experimental results for single carrier hole-only devices using two commonly studied hole transport materials, namely N,N-'-diphenyl-N,N-'-bis-(1-naphthyl)-1-1(')-biphenyl-4,4(')-diamine (alpha-NPD) and 4,4('),4(')-tris(N-3- methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA) are also presented as examples.