Mitigating Edge Etching in Cation Exchange Synthesis of Two-Dimensional Lead Chalcogenide Colloidal Quantum Wells

Two-dimensional colloidal quantum wells are emerging as an exciting class of semiconductor nanocrystals with promising applications in solar cells, owing to their thickness-dependent excitonic properties, including a strong absorption cross-section and suppressed Auger recombination. However, compared to their spherical counterparts, two-dimensional lead chalcogenide-based colloidal quantum wells have not been extensively studied. Among the various synthesis pathways, cation exchange is the most commonly employed approach for synthesizing two-dimensional lead chalcogenide colloidal quantum wells. However, this method often encounters a significant etching problem along the edges of core colloidal quantum wells. To address this issue, we investigated the effect of sidewall protection using core/crown heterostructured cadmium chalcogenide-based colloidal quantum wells in cation exchange experiments. Our results revealed that in CdSe/CdS core/crown nanoplatelets, the etching process was unexpectedly accelerated compared to the bare CdSe core structure, significantly destroying the initial morphology of the core/crown nanoplatelets. In contrast, when using CdSe/CdTe core/crown nanoplatelets, the initial morphology was successfully maintained after the cation exchange. We attribute these results to the different strain states in core/crown heterostructured quantum wells covered with CdS and CdTe, underscoring the importance of strain in cation exchange experiments. This study highlights the critical role of strain in preserving the structural integrity of two-dimensional colloidal quantum wells during cation exchange and provides insights for improving synthesis methods for advanced nanocrystal applications.<br/><br/>This study was partially supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under the grant no. 121C227.