DONOR-ACCEPTOR PAIRS TO LIMIT V(OC)-IMPROVEMENT OF PHOTO-DIODES

When deep-level centers are inserted near the junction interface, the open-circuit voltage of photo-diodes is reduced. The performance degra dation due to the doped layer is sensitively position-dependent; its m aximum effect is at a position where n congruent-to p, for similar rec ombination rates of electrons and holes. In high-efficient solar cells , it is suggested that donor-acceptor pairs that are created by the co nventional diffusion process are responsible for the unintentional lim itation of the open-circuit voltage. Computation of the solution curve s of transport-, continuity-, and Poisson equations for a two-carrier model indicate that the omission of close pairs by insertion of a thin undoped layer (inverse delta-doping), and consequential reduction in the density of distant pairs causes an increase of the open-circuit vo ltage and fill factor without concomitant decrease of the short-circui t current.