High-Gain Self-Powered Photodetector Enabled by Type-II CsPbBr3 Single Crystal Wafer–CdSeS Quantum Dot Heterojunction for Weak Light Photodetection

To address the demand for high-sensitivity photodetectors under weak light conditions, we have designed a Type-II heterojunction photodetector based on CsPbBr3 single crystal wafers (SCWs) and CdSeS quantum dots (QDs). High-quality two-dimensional (2D) CsPbBr3 SCWs were grown using a space confined growth method, while zero-dimensional (0D) CdSeS QDs were prepared by thermal injection. The heterojunctions were constructed by partially coating the CsPbBr3 SCWs with the CdSeS QDs. Due to the staggered energy band alignment, the built-in electric field was established within the interface, significantly enhancing the separation of photogenerated carriers and effectively suppressing nonradiative recombination. Kelvin probe force microscopy (KPFM) measurements confirmed a surface potential difference of 0.69 V, validating the presence of the built-in field. The device exhibited a low dark current of 1.23 × 10-11 A and a detectivity (D*) of 1.2 × 1013 Jones under weak light illumination. At 5 V bias, the device demonstrated an external quantum efficiency (EQE) of 193%, indicating efficient photocarrier extraction. These results highlight the outstanding performance of the CsPbBr3-CdSeS Type-II heterojunction for weak light detection and provide a promising approach for high-performance photodetectors.