CdTe x S1– x Alloy Nanoplatelets with Decoupled Absorption and Emission

Abstract Achieving homogeneous CdTexS1–x alloy nanoplatelets (NPLs) remains a significant challenge owing to disparate chalcogen precursor reactivity and large anion size and orbital mismatch. In this study, homogeneous CdTexS1–x alloy NPLs with various compositions were synthesized by using chalcogen precursors with comparable incorporation kinetics. The resulting alloy NPLs exhibit an unusual optical response, where the excitonic absorption peak initially red-shifts upon sulfur incorporation and subsequently becomes pinned with increasing sulfur content, while photoluminescence red-shifts continuously. This behavior is in stark contrast to conventional CdSexS1–x alloy NPLs, where both absorption and emission progressively blue-shift with increasing sulfur incorporation. The decoupled absorption and emission behavior was found to arise from Te-dominated valence-band pinning, while alloying-induced carrier localization further enhanced photoluminescence efficiency and prolonged exciton lifetimes. This work provides new insights into unconventional band-edge evolution in low-dimensional semiconductor alloys.