Is this too good to be true? Sure!
Accroding to this project, plants are producing enough waste during their photosynthesis that this waste can "be converted to" (?) electricity with the help of special bacteria. This electricity is then made available in the form of an USB connector to charge your phone...
https://www.indiegogo.com/projects/bioo-charge-your-phone-with-the-power-of-a-plant#/They claim an output power of up to 40W per square metre for their full-sized version - even under full sunlight this would still mean an efficiency of 4%, or about 10x as much as is normally assumed for photosynthesis alone...
The project has been taken up in the weekly newsletter from Elektor - as usual without any editorial analysis or comment.