In this Book, back reflectors for hydrogenated amorphous silicon and hydrogenated nanocrystalline silicon based solar cells have been systematically studied. 1) By using the optical scattering theory and PVOPTICS simulation program, it is found that to characterize the texture of the BR, not only texture height, but also the texture angle is needed. It has been deduced that the light trapping scheme with ideal rough BR should have an effective light path enhancement factor of n(n+1)2 in the absorption media, rather than 4n2, the generally quoted value in references. 2) This work studied...