The chart above is spectacular. Above all, zoom in and look at the four yellow and red points at the right.
They represent the performance evolution of a new technology for solar cells that was discovered almost accidentally few years ago. Instead of using pure silicon crystals (whose manufacture is expensive both economically and energetically), a material called perovskite is used. It doesn’t contain expensive nor rare metals.
They have just published that its efficiency has risen till 20%, competing directly with technologies that are already used in a commercial basis. For example, solar cells based on CdTe or also CGIS (cadmium is very toxic, while gallium and indium are rare and not cheap at all)
Perovskite cells are considerably cheaper that actual commercial technologies. They only have a major drawback: They need lead, which is also quite toxic
Recently, it was discovered a way to produce perovskite cells substituting the lead by tin, which solves the toxicity problem. That cell had a performance of only 6%, so economically it is not yet a valid alternative