Enhanced Optoelectronic Response of TiO2 Photodetector Sensitized via CuInSe2 Quantum Dots

Colloidal copper-based chalcogenide quantum dots (QDs), particularly lead-free CuInSe2 systems, have emerged as promising photosensitizers for optoelectronic de-vices due to their high extinction coefficients and solution processability. In this work, we demonstrate a TiO2 photodetector enhanced through interfacial engineering with the size of 9.88 ± 2.49 nm CuInSe2 QDs, synthesized via controlled thermal injection. The optimized device architecture combines a 160 nm TiO2 active layer with 60 μm horizontal channel electrodes, achieving high performance metrics. The QD-sensitized device demonstrates an impressive switching ratio of approximately 105 in the 405 nm wavelength, a significant 34-times increase in responsivity at a 2 V bias, and a detection rate of 4.17 × 108 Jones. Due to the limitations imposed by the TiO2 bandgap, the TiO2 photodetector exhibits a negligible increase in photocurrent at 565 nm. The engineered type-II heterostructure enables responsivity enhancement across an extended spectral range through sensitization while maintaining equivalent performance characteristics at both 405 nm and 565 nm wavelengths. Furthermore, the sensitized architecture demonstrates superior response kinetics, enhanced specific detectivity, and exceptional operational stability, establishing a universal design framework for broadband photodetection systems.