Kw. Boer et J. Piprek, DONOR-ACCEPTOR PAIRS TO LIMIT V(OC)-IMPROVEMENT OF PHOTO-DIODES, Solar energy materials and solar cells, 32(4), 1994, pp. 395-403
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.