Why Asymmetrical Junctions are widely used in Solar Cells? What Advantages?

eserly

Hello,

I was investigating 'Asymmetrical P-N Junctions'.
If the doping concentration of the P and N type semiconductors are different then the P-N junction they will form will be a asymmetrically doped Junction.

I searched and come up with the fact that 95% of the solar cell structures are asymmetrical because they give the best efficiencies.

What are the advantages of these asymmetrical junctions? Why are the efficiencies are high?
If anyone has some information about the subject I'll be very thankful..
Thank You