Construction of solar simulator is quite complicated. Not only the intensity of the light source should be considered (number of lux etc.), but also the spectral response. In other words, not only the total number of photons or the total amount of energy, but also at what wavelength/energy you get these photons. 

For this reason, usually Xe light sources are being used, since their spectral behaviour is closer to that of the standard solar radiation (AM 1.5 G). You can find commercial products of this kind, but they are quite expensive. Alternatively, you can try to couple multiple LEDs of different wavelengths, but this is also quite complicated if you realy want your spectrum to match the solar spectrum, and may require some optical work.

Good luck! 

Right now I am using couple of Halogen lamps used in cars, which is giving the almost the same lux that of sun light.

The flux may be similar, but the spectral distribution is a little different, as you can see here: 

http://zeiss-campus.magnet.fsu.edu/articles/lightsources/images/tungstenlampsfigure3.jpg

The question is whether such a difference is important for you. It depends on the kind of solar cells you work with. It may be good enough for what you need, unless if your solar cells are active mainly in the wavelengths where there is a significant difference between your lamp and the solar spectrum.

Here is some general information about light sources for solar simulation:

http://www.pveducation.org/pvcdrom/characterisation/illumination-sources

David makes a very good point, that the answer depends strongly on the type of solar cell you want to test. Xe arcs are expensive but very close to solar spectrum - yet multilayer cells can still be very sensitive to variations in the spectral distribution. I have a simple emulator which I have used to simulate 4 layer cells, allowing you to set the sensitivities and wavelength cross over points quite accurately. It is amazing how accurate you have to set them! Also, the emulator has spectra  for sunlight, AM 1.5 and Xe arcs, tungsten halogen and fluorescents. You can get 3:1 differences in measured efficiency by changing from Xe arc to halogen. And selecting fluorescents, sometimes the cell doesn't work at all!

Best wishes.

Thank you Tony Maine. I was testing Hybrid Solar cell.

Hi Vadiraj,

Do you perhaps mean a two layer cell? What are the two layers please?

Best wishes

Sir

it a single layer cell, With a polymer and Metal sulphide blend. Coated on ITO glass and Aluminium back coat.