Confined excitons in AgI nanocrystals in crystalline KI matrix

Low-temperature exciton spectra are investigated in AgI nanocrystals in a monocrystalline KI matrix. The occurrence of the Z1,2 together with the A and B exciton absorption bands demonstrate that both zincblende (γ) and wurtzite (β) structure nanocrystals have formed. The exciton blue shift implies a case of weak confinement and an average particle radius of about 2.5nm. Size-selective excitation results in line narrowing and reveals detailed structure in emission due to the LO phonon coupling and the fine structure of the A exciton state. From the analysis the short-range electron–hole exchange energy is found to vary between 2 and 7meV with decreasing particle radius. The origin of another structure with size-dependent energy shift of 7–11meV is discussed. A size-dependent scattering of the B exciton state into the A exciton state is observed.