Photolumi nescence studies
To investigate further optical properties of as prepared Co 2+ doped ZnO nanopowders, room temperature
Photoluminescen ce(PL) studies were carried out at an excitation wavelength of 285 nm. PL spectrum showed emission peaks in the range of 300–500 nm and the correspondi ng spectrum was shown in Fig. 5.In general two peaks are observed in the PL spectrum of ZnO, i.e. in UV and in visible regions. The UV emission is also called as near band edge emission (NBE) originates due to the free-exciton recombinati on while the green emission are also known as deep level
emission (DLE) which appears due to the impurities and structural defects in the grown structure s [22]. The peaks positions of the UV emission are slightly shift to long wavelength for doped sample when compared to undoped sample, showing the red-shift of band gap [30,31].