  We develop nonequilibrium auxiliary quantum master equation dual boson method
(aux-DB), and argue that it presents a convenient way to describe steady states
of correlated impurity models (such as single molecule optoelectronic devices)
where electron and energy transport should be taken into account. The aux-DB is
shown to provide high accuracy with relatively low numerical cost. Theoretical
analysis is followed by illustrative simulations within generic two-level
junction model, where the new scheme is benchmarked against numerically exact
results.
