Room Temperature Size Tuning of CsPbI ₃ Quantum Dots

Size quantization in halide perovskite nanocrystals provides a versatile strategy to tune their optical and electronic properties. We have now synthesized CsPbI3 quantum dots (QDs, 5–13.5 nm) by first preparing CsPbBr3 QDs at room temperature, followed by postsynthetic halide exchange with iodide ions. As the QD size decreases from 13.5 to 5 nm, we observe a pronounced blue shift in both excitonic and emission peaks, accompanied by an increase in the Stokes shift. The reduction in the excited-state lifetime with decreasing QD size is attributed to enhanced intrinsic exciton recombination and a higher density of surface defects. Photoinduced electron transfer between quantized CsPbI3 and methyl viologen revealed an ultrafast process occurring within a few picoseconds. These size-dependent excited-state dynamics and charge-transfer properties highlight the potential of CsPbI3 QDs for photocatalytic solar fuel generation and optoelectronic applications.