We demonstrate organic residue free,bandgap-graded Cu2Zn(Sn1–xGex)S4(CZTGeS) thin-filmsolar cells based on metalchalcogenide complex (MCC) ligand capped nanocrystals (NCs). The bandgapof the CZTGeS films is tuned by varying the amount of Sn2S64–MCC ligand absorbed on the surfaceof the Cu2ZnGeS4(CZGeS) NCs, without an undesirablepostselenization process. Using CZGeS NCs inks with three differentSn/(Ge+Sn) ratios, bandgap-graded CZTGeS thin films are obtained viamulticoating and annealing procedures. Compositional and spectroscopicanalyses along the film thickness confirm that the band-graded CZTGeSabsorber layer, with a gradually increasing bandgap from the backcontact to the p–njunction,is successfully accomplished. Compared with an ungraded band structuredCZTGeS cell, this normal grading structure facilitates both highershort circuit current and open-circuit voltage, facilitating a powerconversion efficiency of 6.3%. [ABSTRACT FROM AUTHOR]