This paper presents the development and implementation of a high-sensitivity external quantum efficiency (sEQE) measurement system designed to characterize optoelectronic de- vices, particularly solar cells and photodetectors. Our setup enables precise measurement of the conversion efficiency of photons into free charge carriers, providing crucial insights into device performance and underlying physical mechanisms. The measurement setup is based on a white-light source coupled to a monochromator for wavelength selection, with the diffracted beam focused onto either a calibrated photodiode or the device under test. Mea- surements can be performed at room temperature using a custom sample holder or across a range of temperatures using a cryostat. Signal detection is achieved through Lock-In amplifi- cation, enabling high sensitivity in noisy environments. The incorporation of spectral filters and multiple photodiodes with extended calibration ranges enables a dynamic range span- ning six orders of magnitude, allowing detection of sub-bandgap signals. Beyond describing component modularity and hardware specifications, we provide open-source Python-based control and analysis software to control the sEQE setup and analyze the resulting data. This comprehensive documentation of both hardware and software components contributes to an ongoing effort to increase transparency, standardization, and reproducibility in experimental research and aims to ease access to an important characterization technique for solar cells and photodetectors.
Jungbluth et al. (2025) studied this question.