Improved thin-film photovoltaic devices and methods of manufacturing such devices are described. Embodiments include a substrate-configured thin-film PV device (200) having a photo-absorbing semiconductor layer (230) and a window layer (240). Embodiments include devices having a CdTe photo-absorbing semiconductor layer, a CdS or CdS:In window layer, and an n-p junction residing at or proximate an interface of the photo-absorbing semiconductor and window layers. Variations include methods of manufacture wherein i) O.sub.2 is excluded from an ambient environment during deposition of the CdTe layer (102), ii) O.sub.2 is included in an ambient environment during CdCl.sub.2 treatment (103), iii) O.sub.2 is included in an ambient environment during deposition of a CdS or CdS:In layer (104), or iv) a medium-temperature anneal (MTA) having an anneal temperature of 300.degree. C. or less is performed (105) after deposition of the CdS layer.
 The United States Government has rights in this invention under Contract No. DE-AC36-080028308 between the United States Department of Energy and the Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory.