Photovoltaic Cells are improving radically for space applications

Advances in solar cells, materials, electronics, and in-space manufacturing have reduced the minimum size of a space based solar power plant exponentially since the first designs proposed in the 1970's. Using data from ESA SOLARIS and Roland Berger [1], the trendline for space based solar power (SBSP) shows the required launch mass dropping by an order of magnitude about every 25 years. In other words, even if launch costs stay the same, the costs to launch a SBSP satellite can be expected to continue dropping at about 8% year.

This trend should continue. Ultimately, sunlight can be transformed into beamed power in films a few nanometers thick. [2] All of the technologies to make this happen will continue to improve.

[1] https://www.esa.int/Enabling_Support/Space_Engineering_Technology/SOLARIS/Cost_vs._benefits_studies
[2] https://en.wikipedia.org/wiki/Thin-film_solar_cell