Mechanism of Enhancement of Stokes Shifted Photoluminescence Quantum Yield and Lifetime from Ag(I)-Doped CdSe Nanotetrapods: Implications for Optoelectronic and Photonic Devices

Ag(I)-doped CdSe nanotetrapods (NTPs) have been prepared using the post-synthesis cation exchange method. The shape and crystal structure of NTPs are found to be conserved after doping. The photoluminescence (PL) spectrum is Stokes shifted by 110 nm (0.33 eV) in doped NTPs at the highest dopant content (0.6%). The PL quantum yield increases to 11% from a value of 1.6% in undoped NTPs, with the emergence of a new, significantly longer component with a lifetime of 143 ns, at the cost of the fastest, nanosecond or lower component in the undoped NTPs. The dynamics of hole capture, which is the primary photoprocess that brings about the PL enhancement, has been elucidated by ultrafast transient absorption spectroscopy. Hence, Ag-doped colloidal three-dimensional NTPs are shown to be promising photoluminescent materials, which are less likely to suffer from the issue of the reabsorption of emitted photons due to the large Stokes shift emission. There are immense possibilities for their application in colloidal nanocrystal-based optoelectronic and photonic devices like light-emitting diodes and luminescent solar concentrators.