Research Highlights

 

Rainbow colours out of a Mn ion: Doped semiconductors as the future of lighting

 

- D D Sarma, Solid State and Structural Chemistry Unit

In this paper (http://link.aps.org/doi/10.1103/PhysRevLett.110.267401), it has been shown that Mn ions, embedded (or doped) in very small-sized semiconductor matrices, can emit colors from almost blue to all the way to deep red covering most of the visible light spectrum. This is surprising because all previous works reported Mn light to be essentially in the orange-red region. Getting light of different colors from any system is technologically important, as such systems can be used for a range of applications - from highly efficient display screens on computers, laptops and TVs to lighting of rooms in an energy efficient manner.

This work looked at the problem of Mn light emission from such very small-sized semiconductor matrices through a microscope, thereby looking at individual units, while all previous studies looked at a collection of a large number of matrices assuming each individual one behaves more or less the same way. The surprising discovery here is that in reality each matrix has Mn emitting a different color, depending on how far from the surface of the matrix the Mn ion resides, the earlier reported orange-red color being a result of all different colors overlapping with each other. This realization opens up huge technological possibilities to use Mn doped semiconductor matrices for a wide range of energy efficient lighting applications.

This work has been highlighted in the “FOCUS” section of “Physics” published by the American Physical Society, and can be accessed at http://physics.aps.org/articles/v6/73. It has also been covered by Nature India (doi:10.1038/nindia.2013.91; Published online 12 July 2013).

 

 

 

 

 

 

 

 

 

 

 

Fig. 1:   A  schematic  of  Mn emission spectra

from an ensemble of Mn-doped  nanoparticles

(bold yellow broad envelop spectrum) and from some representative individual single nanoparticles(the five thin sharp component spectra). Left inset shows colour of ensemble emission and right inset shows colour from individual doped nanoparticle emissions.       

 

 

Fig. 2: Emission positions of individual doped

nanoparticles  as  CIE  diagram,  which shows

the Mn emission coverage from green to red in the visible range.