Simultaneous determination of built-in voltage and charge carrier mobility in organic diodes from light intensity dependent current–voltage characteristics

Abstract

Built-in voltage (Vbi) and charge carrier mobility are essential parameters of organic diodes, such as organic photodiodes, organic light-emitting diodes and organic solar cells. The existing methods for charge carrier mobility measurement require either expensive equipment, or stringent sample preparation. We demonstrate a method that simultaneously determines the Vbi and charge carrier mobility in organic photodiodes and solar cells from incident light intensity dependent current–voltage characteristics. The Vbi is determined from the saturation open-circuit voltage, while the charge carrier mobility from the space-charge limited photocurrent. The Vbi for organic diodes, ‘ITO/copper phthalocyanine (CuPc)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/Al’, ‘ITO/ lead phthalocyanine (PbPc)/BCP/Al’, ‘ITO/CuPc/C60/BCP/Al’, and ‘ITO/PbPc/C60/BCP/Al’, were measured to be 0.583 ± 0.019, 0.458 ± 0.002, 0.605 ± 0.009 and 0.538 ± 0.004 V, respectively; the hole mobility of CuPc and PbPc thin films were measured to be (1.383 ± 0.367) × 10−6 cm2 V−1 s−1 and (3.675 ± 0.887) × 10−6 cm2 V−1 s−1, respectively. The measured values for Vbi and carrier mobility coincide with related experimental results reported in other literature.