I think he may be underestimating the future efficiency gains.
There is already 30% efficient directly illuminated multi-junction PV on the market ( http://www.emcore.com/wp-content/uploads/ZTJ-Cell.pdf ), they are just so damn expensive at the moment that only the space industry are using them.
Also, while it is a huge amount of work, it is no worse than many other industries, the economics are starting to make it a good investment for big finance, and we are not likely to run short of either silicon or lithium along the way.
There is already 30% efficient directly illuminated multi-junction PV on the market ( http://www.emcore.com/wp-content/uploads/ZTJ-Cell.pdf ), they are just so damn expensive at the moment that only the space industry are using them.
Also, while it is a huge amount of work, it is no worse than many other industries, the economics are starting to make it a good investment for big finance, and we are not likely to run short of either silicon or lithium along the way.