KF Postdeposition Treatment in N-2 of Single-Stage Thin Cu(In,Ga)Se-2 Absorber Layers

Abstract

Thin (<500 nm) single-stage coevaporated Cu(In,Ga)Se-2 absorber layers are treated with a KF postanneal in N-2 atmosphere. The conditions of the postanneal initial acceptor concentration and the temperature are varied. Solar cells are characterized with current-voltage and capacitance-voltage measurements. Efficiencies up to 12% with an open-circuit voltage (V-oc) of >640 mV were achieved after the KF treatment. From SCAPS simulations and temperature dependent current voltage-measurements, it is concluded that the V-oc of these cells are limited by backcontact surface recombination and, thus, further improvements require passivation of the back contact.