Study concludes that 'rona exposed to sunlight effectively eliminated infectivity in 7-10 minutes. No sunlight, such as indoors, can allow it to remain active for ~6 hours.
Temp and humidity also play a part in this, but optimal combinations were not discerned.
Unrelated to the study, I've read others indicate that "if sunlight is so good, why are places like AZ & FL have so many cases in the hotter months". The simple answer is most likely everyone is indoors using AC during those hotter days, where the bug has a better chance of spreading.
The study did not discuss how much longer a mask enables the virus to remain active and infectious given that the mask would shield the virus from UV and enable it to remain active for 6+ hours, spreading each time the mask was fiddled with (ie constantly).