A main strategy to enhance the efficiency of single crystal silicon is maximizing absorbtion and minimizing reflection.
Producing inverted pyramids on the surface allows light to be absorbed more readily. With inverted pyramids, it takes two reflections instead of one for photons to be lost due to reflection. Photons traveling into the material enter at an angle as well, increasing the path length inside the material.
Metal contacts on the front surface reduce the area for light absorbtion. By embedding the contacts into the silicon, a larger contact to silicon surface area is achieved while minimizing the loss of absorbtion surface area. The area that surrounds the contact is more heavily doped to improve conductivity.
Enhancing efficiency through a reduction in recombination
As electrons or holes reach the surface, minute topographical defects can trap them. Recombination is more likely to occur when either a hole or electron is stationary. Oxidizing the surface creates an inert layer which keeps carriers from reaching the surface and becomming trapped.
Oxidizing the rear surface and using point contacts also increases efficiency by reducing rear surface recombination.
Enhancing efficiency through a reduction in resistance
A main source of series resistance is at the contact points. By differentially doping around the contact point, conductivity is improved and losses due to resistance are minimized.