Innovative fabrication of low-cost kesterite solar cells for distributed energy applications

We present the results of three novel approaches to the fabrication of kesterite solar cells from scalable, Cu
₂
ZnSnS
₄
(CZTS) nanoparticle inks. Firstly, CZTS nanoparticles are annealed in a Se-rich atmosphere inside a transmission electron microscope (TEM). This allows observation of the thin film PV absorber formation in real-time and provides the new insight that chalcogen atom exchange and grain growth occur in different temperature regimes. Secondly, we demonstrate an approach to alkali doping Cu
₂
ZnSn(S,Se)
₄
PV absorbers on flexible Mo-foil substrates that is compatible with high volume manufacturing. Adding NaF directly to the CZTS nanoparticle ink promotes grain growth and improves the device efficiency to 4.4%. Lastly, In
₂
S
₃
/CdS dual buffer layers are investigate to reduce the usage of Cd and result in device efficiency of 7.8% on a glass substrate.