Interparticle Interaction Matters: Charge Carrier Dynamics in Hybrid Semiconductor-Metal Cryoaerogels

Integration of noble metals into semiconductor-based nanoparticle gel structures facilitates the extraction of photoexcited charge carriers upon illumination. While charge carrier generation takes place in the semiconductor component, noble metals in contact to the semiconductor act as electron sinks. Thus, the nature of the interface between the components is of essential importance, as it dictates the characteristics of the interparticle contact. Here, the influence of the nanoscale building block design on the charge carrier dynamics in cryoaerogels consisting of CdSe/CdS nanorods and nanoplatelets as well as of gold or platinum is reported. It is shown that direct growth of noble metal domains onto the semiconductor prior to the gelation significantly facilitates charge carrier separation in their cryoaerogel structures compared to gels from the colloidal mixtures of semiconductor and noble metal nanoparticles, the latter ones having less defined metal/semiconductor boundaries and much more arbitrary component distributions. Although the structure of the different cryoaerogel systems is similar at the micro- and macroscale, nanoscale differences caused by the two synthetic routes drive essentially different behavior regarding the charge carrier dynamics efficiency. These effects are observed spectroelectrochemically via intensity-modulated photocurrent spectroscopy emphasizing the importance of the semiconductor-metal connection in the hybrid structures.