Long-Range Hot-Carrier Transport in Topologically Connected HgTe Quantum Dots

The utilization of hot carriers as a means to surpass the Shockley-Queasier limit represents a promising strategy for advancing highly efficient photovoltaic devices. Quantum dots, owing to their discrete energy states and limited multi-phonon cooling process, are regarded as one of the most promising materials. However, in practical implementations, the presence of numerous defects and discontinuities in colloidal quantum dot (CQD) films significantly curtails the transport distance of hot carriers. In this study, the harnessing of excess energies from hot-carriers is successfully demonstrated and a world-record carrier diffusion length of 15 µm is observed for the first time in colloidal systems, surpassing existing hot-carrier materials by more than tenfold. The observed phenomenon is attributed to the specifically designed honeycomb-like topological structures in a HgTe CQD superlattice, with its long-range periodicity confirmed by High-Resolution Transmission Electron Microscopy(HR-TEM), Selected Area Electron Diffraction(SAED) patterns, and low-angle X-ray diffraction (XRD). In such a superlattice, nonlocal hot carrier transport is supported by three unique physical properties: the wavelength-independent responsivity, linear output characteristics and microsecond fast photoresponse. These findings underscore the potential of HgTe CQD superlattices as a feasible approach for efficient hot carrier collection, thereby paving the way for practical applications in highly sensitive photodetection and solar energy harvesting.