Benchmarking Organic Photodiodes at the Noise Floor

Abstract

Organic photodiodes (OPDs) are considered a next-generation technology for light sensors. However, concerns have arisen regarding the reliable reporting of device performance, particularly under low illumination conditions. The potential factors range from instrumental limitations to questionable assumptions. This work addresses these concerns. The standardized metrics for photodetection are revisited to draw inferences for implementing an appropriate measurement setup and methodical approach for reporting the following steady-state metrics: dark noise, dark current, photocurrent, specific detectivity, responsivity, and (linear) dynamic range. The setup involves a highly sensitive electrometer capable of recording down to femtoampere currents, calibrated optical filters to accurately tune the incident optical power over 12 decades, illumination sources with narrowband emission spectra, baffle plates for stray light mitigation, and a light-tight metallic box to shield the setup from ambient electromagnetic fields. Thorough information on each component, its calibration details, and open-source Python scripts to run the experiments are provided. Subsequently, an OPD and a reference silicon photodiode are characterized, and the accuracy and reliability of the setup are validated. Essentially, this work provides a robust framework to accurately measure and reliably report the standardized photodetecting metrics of next-generation photodiodes.