Self-Powered ZnO Quantum Dot/Si Photodetector with Light-Trapping Inverted Pyramid Structure and High Detectivity

ZnO-quantum dots (QDs) have recently emerged as an attractive material system for photodetection, owing to their size-dependent band structure and pronounced surface effects. Their capability to alleviate interfacial strain at the nanoscale further supports their integration into self-powered devices. In this study, a heterojunction photodetector (PD) based on an ITO/ZnO-QDs/Si/Ag configuration was developed. The device was constructed on a p-type Si substrate featuring an inverted pyramid (IPA) texture, obtained through metal-assisted chemical etching (MACE). A ZnO-QDs layer was subsequently deposited via spin coating, followed by the formation of ITO and Ag electrodes using magnetron sputtering. Under zero-bias conditions and 365 nm illumination (3 mW/cm2), the device delivers a responsivity (R) of 110 mA/W and a specific detectivity (D*) of 3.5 × 1013 Jones, together with a response time of 76.1 ms. Notably, stable photoresponse can still be resolved at light intensities as low as 500 μW/cm2. This behavior is closely related to the internal electric field established at the heterojunction interface. In addition, the textured Si surface increases the effective contact area, while the modified junction properties reduce carrier transport barriers. These factors jointly facilitate the separation and extraction of photogenerated carriers without the need for external bias. The present device architecture therefore provides a viable route toward broadband, self-powered photodetection with high sensitivity.