A comparative study on photon recycling effects in n/sup +/-p and p/sup +/-n InP solar cells with Bragg reflector

Abstract

Numerical calculation of photon recycling (PR) effect has been carried out for n/sup +/-p and p/sup +/-n structure InP cells with Bragg reflector (BR). For both structures with a thin (/spl lsim/ 0.1 /spl mu/m) emitter, PR effects on photocurrent are scarcely observed. A large contribution of PR to photocurrent is found for an n/sup +/-p structure with a thick (/spl gsim/0.5 /spl mu/m) emitter although photocurrent itself is reduced. A p/sup +/-n structure with a similar configuration, on the other hand, shows very small PR effects. Such a difference in the magnitude of PR effects between both cell structures is brought by the difference in radiative and nonradiative lifetimes between n/sup +/ and p/sup +/ emitters. An increase in Voc is found for an n/sup +/-p cell with a thin (/spl sim/2 /spl mu/m) base layer. As results of increases in photocurrent and Voc by PR, conversion efficiency of a n/sup +/-p cell is increased by about 3%. For both cell structures, PR effects are observed for a base thickness less than about 3 /spl mu/m. The effects are not due to the trapping of re-emitted light but the trapping of incident light.