Super Bending-Stable Flexible Colloidal QD Photodetector with Fast Response and Near-Unity Carrier Extraction Efficiency

Flexible colloidal quantum dot (QD) optoelectronics apply the superior properties of colloidal QDs to flexible devices, exhibiting unique advantages in the fields of imagers, solar cells, displays, wearable sensors, on-skin electronics, robotics, and bioimaging. Here, we show that colloidal QD photodiodes (QDPDs) with an ultrathin QD absorber layer have record bending stability with 100,000 repetitive bending cycles in QD devices. The QDPDs obtained a high-quality p-n junction with a 1700 rectification ratio. The formation of a Fabry-Pérot cavity by the layered stack results in a 3.4-fold enhanced light absorption, while the ultrathin structure ensures a near-unity efficient extraction (97%) of photogenerated charge carriers from the PbS QD film upon illumination with 1330 nm short-wavelength infrared light. Finally, upon suppression of the capacitance effect, the response time of this QDPD can be as short as 20 ns, which is the fastest response for flexible colloidal QDPDs.