We observe competition between picosecond photoinduced absorption and
stimulated emission in poly(paraphenylenevinylene) which demonstrates
that they derive from two different pathways. We conclude that the pho
toinduced absorption originates from nonemissive ''spatially indirect'
' singlet excitons which are formed with quantum yield as high as 0.9.
Previous arguments about maximum possible electroluminescence device
efficiencies and about lasers in conjugated polymer films are reexamin
ed in light of the prevalence of this species.