Recent calculations of the electron affinity difference between CdS and CuInSe2indicate that the conduction band (CB) minimum of CuInSe2is below the CB minimum of CdS. As a consequence, a spike occurs in the CB at the CdS/CuInSe2interface. Such a spike is commonly considered as in conflict with good photovoltaic performance of heterojunction solar cells. It is outlined here that the simple assumption of thermionic emission across the junction can explain an unimpeded electron transport in the case of ann+pstructure (n‐type window,p‐type absorber), even when a spike in the CB occurs. ©1995 American Institute of Physics.