I think it will be more important to have a material that re-radiates long wave IR poorly (because that is where the panel will lose heat) yet absorbs short wave IR well (because that is where the panel absorbs heat). If surface treatments assist with this, all well and good. Best wishes with your research.

Thanks@Tony maine, In solar absorber hemispherical shapes are used for long IR wave scattered into low IR waves and that absorbed by any one of the coated layers in the absorber. 

My question, Is the same kind of scattering long IR and absorb low IR waves behaviour applied in solar thermal absorber surface is possible. ...likely in solar flat plate copper(or) any  absorber bed.

Yes, the Australian CSIRO devised a surface treatment may years ago that did this.