How do they compare in efficiency per m2 with regard to converting light into respectively chemical and electrical forms of energy?
It’s very hard to give any direct comparisons becaue they work very differently. Photoelectric cells convert light into energy and that’s all they are designed to do. Plants convert light into energy but they need to use a lot of that energy to maintain themselves.
Photovoltaic cells can be arragend in a single flat layer. Plants arent designed that way generally, and as a rsult the don’t intercept the sunlihgt quite as directly, but they have more height over whch to do so.
In general photvoltaic cells convert about 12% of the light striking them into electrical energy. In ocntrast plants convert only about 1%. However plants will need to use most of that energy just to maintain themselves, so human utilisable energy efficiency. will be even less, possibly as low as .1%. Of ocurse that’s a bit of an unfair comparison because photovoltaic cells need to be manufactured using energy too.