Maddox Le

Project: Organic Photodetector Optimization, Short-Wave Infrared Sensing

Lab Group: Nguyen Lab

Graduate Mentor: Zhongze Jason Qu

Many technologies rely on inorganic photo detectors to convert shortwave infrared (SWIR) light into electric signals under high voltage. However, inorganic photo detectors are brittle resulting in an expensive fabrication process with a lack of flexibility. In this project, we optimized organic photodetectors (OPDs) that aim to address the issues of inorganic photo detectors specifically in the SWIR. Our results show that changing the device structure from inverted ZnO/PCE10:COTIC-4F/MoO_x to a conventional structure of CPE-Ph/PCE10:6CN/C_60, achieved an improvement in EQE of 25% at 1200 nm under a −5 V bias. The same structure also showed a significant decrease in dark current (J_d) from 5.81E−7 A×〖cm〗^(-2)  to 2.79E−7 A×〖cm〗^(-2)  at −5 V, showing a 52% decrease. The new device structure also reported an improved linear dynamic range at 1200 nm of 121 dB at a −5 V bias. The new device structure also maintained stable speed, quantified by the 3 dB cut-off frequency (f3dB) at 1200nm of 55.4 kHz, similar to that of the inverted structure of 52 kHz at 940nm at −5 V Bias. Most importantly, the overall result shows an increase in specific detectivity (D*) for the 1200 nm SWIR light, which jumps from 4.20E11 Jones to 7.96E11 Jones showing an increase of 90%. The research shows an impressive improvement of SWIR detecting performance when using CPE-PH as an interlayer instead of ZnO.