Multi-spectral GeSe/PbTe phototransistor for wearable optical medicine

Flexible photodetectors play a crucial role in improving human healthcare. However, the narrow spectral detection range, poor stress stability, and non-degradability of traditional flexible photodetectors significantly hinder the further development of wearable medical devices. In this study, a printable phototransistor was developed with excellent dynamic performance (detectivity of 7.2 × 10¹² Jones, responsivity of 6.7 A/W, and response/recovery time of 70-72 ms, along with good mechanical stability) modulated by the GeSe/PbTe heterostructure in the short-wave infrared (SWIR) range and further optimized the optoelectronic performance through in-plane anisotropy. In addition, the electrode pattern of the detector adopts a square spiral interdigitated design, which integrates with the vertical heterostructure to increase the photosensitive and sensing areas. This GeSe/PbTe-based phototransistor, combined with a designed flexible printed circuit board (FPCB), extracts PPG signals and utilizes a partial least squares regression model to predict blood glucose levels with a relative error of 10%. Multi-spectral design can assist PPG flexible sensors in filtering out noise interference from complex blood echoes and extracting more effective short-wave infrared information, thereby providing doctors and patients with more accurate (correlation coefficient R = 0.928) medical insights.