title: Efficient solid-state light-emitting CuCdS nanocrystals synthesized in air.
abstract: Semiconductor nanocrystals (NCs) possess high photoluminescence (PL) typically in the solution phase. In contrary, PL rapidly quenches in the solid state. Efficient solid state luminescence can be achieved by inducing a large Stokes shift. Here we report on a novel synthesis of compositionally controlled CuCdS NCs in air avoiding the usual complexity of using inert atmosphere. These NCs show long-range color tunability over the entire visible range with a remarkable Stokes shift up to about 1.25 eV. Overcoating the NCs leads to a high solid-state PL quantum yield (QY) of ca. 55% measured by using an integrating sphere. Unique charge carrier recombination mechanisms have been recognized from the NCs, which are correlated to the internal NC structure probed by using extended X-ray absorption fine structure (EXAFS) spectroscopy. EXAFS measurements show a Cu-rich surface and Cd-rich interior with 46% Cu(I) being randomly distributed within 84% of the NC volume creating additional transition states for PL. Color-tunable solid-state luminescence remains stable in air enabling fabrication of light-emitting diodes (LEDs).
authors.affiliation: Centre for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India).
authors.forename: Ali Hossain
authors.initials: AH
authors.lastname: Khan
authors.forename: Amit
authors.initials: A
authors.lastname: Dalui
authors.forename: Soham
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Carlo U
authors.initials: CU
authors.lastname: Segre
authors.forename: D D
authors.initials: DD
authors.lastname: Sarma
authors.forename: Somobrata
authors.initials: S
authors.lastname: Acharya
keywords: EXAFS spectroscopy; alloys; colloid synthesis; fluorescence spectroscopy; light emitting diodes