Crystalline silicon cells are already inexpensive, non-toxic, and long-lived. So it makes sense that most researchers are looking for higher efficiency. Back when purified silicon prices spiked around 2007-2008 there were a lot of efforts looking into more affordable (if less efficient) thin film based materials, but those fizzled out as wafered silicon got cheap again and kept widening the efficiency gap over e.g. amorphous silicon.

Since there's also a much bigger solar industry today than in 2007, you also see more practically-minded research coming out of corporate centers (Longi, Oxford PV, GCL System Integration, and others working on perovskite cells and perovskite-silicon tandems). Since they care about shipping real products, they are focused on solving lifetime and durability issues. Of course since this research can give a big commercial edge as single junction silicon reaches its efficiency limits, you'll also only see the really promising work published after it is patented.