An innovative alkali doping strategy for Cu2ZnSnSe4 through the CdS buffer layer

Alkali doping (Li, Na, K) has shown to be very relevant for obtaining high efficiency kesterite solar cells. Conversely to absorbers produced by chemical routes, the doping with very low alkaline contents of absorbers prepared by PVD routes is very complex. In this work we present an innovative approach based on the introduction of alkali-citrates during the CBD process of CdS, for the selective doping of Cu
₂
ZnSnSe
₄
/CdS interface. We demonstrate that this simple strategy is very useful for incorporating the alkalis into the system, reporting efficiencies over 10% for the K doped CdS.