We observe and study the anomalous Stokes shift of CuAlS/CdS quantum dots. While all known I-III-VI semiconductor core/shell quantum dots show Stokes shifts in excess of 100 meV, the shift associated with CuAlS/CdS quantum dots is uniquely large, even exceeding 1.4 eV in some cases. CuAlS/CdS quantum dots are thus associated with cross sections less than 10 cm under the emission maximum. We investigate this anomaly using spectroscopic techniques and ascribe it to the existence of a strong type-II offset between CuAlS and CdS layers. Besides their strong Stokes shift, CuAlS/CdS quantum dots also exhibit high quantum yields (63%) as well as long emission lifetimes (∼1500 ns). Because of the combined existence of these properties, CuAlS/CdS quantum dots can act as tunable, transparent emitters over the entire visible spectrum. As a demonstration of their potential, we describe the construction of a wide area transparent lighting device with waveguided optical excitation and a clear aperture of 7.5 cm.

In the present work, the microcrystalline characteristics of KBr thin films have been investigated by evaluating the breadth of diffraction peak. The Williamson-Hall, the Size-Strain Plot and the single line Voigt methods are employed to deconvolute the finite crystallite size and microstrain contribution from the broaden X-ray profile. The texture coefficient and dislocation density have been determined along each diffraction peak. Other relevant physical parameters such as stress, Young's modulus and energy density are also estimated using Uniform Stress Deformation and Uniform Deformation Energy Density approximation of Williamson-Hall method.

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