  The bulk photovoltaic effect (BPVE) -- generation of electric currents by
light in noncentrosymmetric materials in the absence of electric fields and
gradients -- has been intensively investigated in the end of the last century.
The outcomes including all main aspects of this phenomenon were summarized in
review and books. A new upsurge of interest to the BPVE occurred recently and
resulted in a flux of misleading theoretical and experimental publications
centered around the so-called shift current. Numerous top-rated recent
publications ignore the basic principles of charge-transport phenomena and the
previous results of joined experimental-theoretical studies. Specifically,
dominating (or substantial) contributions to the currents caused by asymmetry
of the momentum distributions of electrons and holes are missed. The widespread
starting relation for the shift current, originating from the quadratic
nonlinear response theory and pretending to be omnipotent, is in fact
incomplete. It ignores kinetic processes of relaxation and recombination of
photo-excited electrons and leads to non-vanishing shift currents in thermal
equilibrium. The goals of this methodical note is to specify and argue the
benchmarks of the BPVE theory and return the studies on the right track in the
interest of development of photovoltaic devices.
