Device characterization Electroluminescence spectra were captured using an Ocean Insight QE Pro with voltages sourced to the device from a pre-programmed Keithley 2400. J-V-L characterizations from 0 V-10 V with a voltage scanning step of 0.4 V were performed using an HP4145A and a calibrated Thorlabs photodiode (FDS1010-CAL) mounted just above the face of the device.