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 CsPbI 3 quantum dots (QDs, 5–13.5 nm) by first preparing CsPbBr 3 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 CsPbI 3 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 CsPbI 3 QDs for photocatalytic solar fuel generation and optoelectronic applications.