Explain "photovoltaic" to 3rd grade science class!

Going further, search internet for recent research articles, press releases, and other sources introducing innovations in photovoltaic technology (not necessarily commercialized).

• (i) why is this innovation attractive (main gains/advantages)
• (ii) are there any disadvantages compared to the baseline technology (crystalline silicon)
• (iii) what is the operational principle and what materials are used? Are there any foreseen constraints if this technology is to be scaled up?

Please include links and references to the information you used.