Coupled Self‐Scintillation and Photodetection in PbS Quantum Dots/Graphene X‐Ray Detectors

ABSTRACT Colloidal quantum dot/graphene (QD/Gr) nanohybrids rely on strong quantum confinement and offer a promising platform to design high‐performance quantum sensors such as photodetectors. In QD/Gr nanohybrid photodetectors, QDs absorb the incident light, and the spectral range is determined by the QD's semiconductor bandgap with moderate tunability by QD size, which presents a challenge for QDs/Gr nanohybrids to be used for detection of photons beyond such a conventional bandgap‐determined spectral range. In this work, we explored coupled self‐scintillation and X‐ray photodetection in PbS QD/Gr nanohybrids of sub‐micron active layer thickness for compromised X‐ray self‐scintillation by Pb of high X‐ray cross section and high‐gain detection enabled by graphene on both rigid and flexible substrates. An additional critical step found to suppress noise induced by interaction of polar molecules with dangling bonds on the QD surface was achieved by a poly(methyl methacrylate) capping layer, resulting in significantly improved signal‐to‐noise ratio. This allows a maximum X‐ray sensitivity of 280 C Gy ^{− 1} cm ^{− 2} , together with high responsivity in visible to infrared range on the order of 10 A/W. This result has demonstrated that the conventional bandgap‐determined spectral range can be significantly expanded through design of the QD/Gr nanohybrids. The demonstrated performance and mechanical flexibility provide a pathway toward durable, flexible quantum dot‐based detectors for multi‐spectrum sensing.