From the other earlier research, the influence of the decreasing of gallium content from the buffer layer towards the notch of the absorber can enhance the electrons generated within the space-charge region
Carrier capture within local space-charge region
fields seems to be modified by potential barrier.
where q is the electron charge, [n.sub.i] is the intrinsic concentration, k is the Boltzmann coefficient, T is the absolute temperature, [[tau].sub.p0] and [[tau].sub.n0] are capture times of the charge carriers, [[Delta]w.sub.t] is the energy gap, [l.sub.2n] is the thickness of the space-charge region
and [S.sub.2] is the junction area.
Under the weak light illumination the electron-hole pairs were spatially separated by the disordered local p-n junctions and then the separated electrons and holes drifted towards the side of substrate and electrolyte, respectively, due to the electric field within the space-charge region
, so the efficiency could be relatively high for the weak illumination.