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

Built-in voltage (V-bi) 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) x 10(-6) cm(2) V-1 s(-1) and (3.675 +/- 0.887) x 10(-6) cm(2) V-1 s(-1), respectively. The measured values for V-bi and carrier mobility coincide with related experimental results reported in other literature.