SCLC mobility measurements

The hole-only device structure is ITO/PEDOT:PSS (40 nm)/active layer/MoO₃ (10 nm)/Al (100 nm) and the electron-only device structure is ITO/PEIE (10 nm)/active layer/Ca (20 nm)/Al (100 nm). J–V plots in the range of 0–10 V of the devices were measured using a Keithley 2400 source meter. The hole and electron mobilities were estimated using space-charge-limited current (SCLC) method by fitting the J–V plots near quadratic region according to the modified Mott-Gurney equation:

Where J is the current density, ε₀ is permittivity of free space, ε_r is the relative permittivity (assumed to be 3), μ is the zero-field mobility, V is the potential across the device (V = V_applied -V_bi - V_series), L is the thickness of active layer, and β is the field-activation factor. The series and contact resistance of the device (10–20 Ω) were measured using blank device of ITO/PEDOT:PSS/MoO₃/Al or ITO/PEIE/Ca/Al.