A generalized and robust method for efficient thin film photovoltaic devices from multinary sulfide nanocrystal inks

A generalized and robust method using multinary sulfide nanocrystals for the fabrication Cu(In, Ga)(S, Se)
₂
CIGSSe and Cu
₂
Zn, Sn(S, Se)
₄
CZTSSe thin films and photovoltaic (PV) devices has been developed. By direct synthesis of the multinary sulfide nanocrystals with controlled stoichiometry, superior composition uniformity can be achieved inherently. Using standard device structure, PV devices yield total area power conversion efficiencies (PCE) as high as 12.5% and 7.2% for CIGSSe and CZTSSe respectively, under AM1.5 illumination without anti-reflective coating. By incorporating Ge into the CZTS nanocrystal and adjusting the Sn/Ge ratio, band gap optimization of the CZTSSe absorber film can be accomplished. Despite little optimization, CZTGeSSe has yielded promising results by improving the total area PCE to 8.4%.