Multijunction cells provide greater efficiency because the light is absorbed in chunks using several junctions, each one for definite set of frequencies, while single junction photovoltaic cells take all in one. There are different models on multijunction cells, but the principle is practically the same, with a chance of achieving the highest theoretical efficiency limit of 87%, at least from the usual spectrum to harvest energy, without considering other frequencies like UV or IR.
To wait for the next technologies could be an error as single junction solar cells are in the present time a very interesting choice since efficiency is enough for not occupying a lot of space. With a book sized foldable solar panel, the user can charge a 5V device (smartphone, tablet, other USB devices, …) even faster than with some conventional chargers plugged to the power outlet. With this size they have 7W, 10W, so the current surpasses the one ampere mark easily.
The future is coming though, because that power output is at around 17%-22% efficiency. The market usually presents these efficiencies for reasonably priced solar panels. Foldable solar panels can be purchased at eBay or other source for about $30/25€, and are a wonderful companion for outdoor adventures, beach, camping, public parks, … a nice way to discover how the energy is free like the air.
Although with multijunction cells or another trick for increasing efficiency, with the same size the output is proportional to the increase. With 50% efficiency (or even a bit less) any smartphone could include a solar panel perhaps for standalone operation or for sure focusing auto-charging, providing reasonably quick charging times. Same for other kind of portable technology, and of course electric vehicles.
Although the solar industry is constantly growing, sometimes the prices continue being the biggest setback. Decades ago, solar energy was far from accessible, although nowadays the things are changing. The near future should finally correct this problem remembering the wonders or large numbers, and as fast as possible to fight air toxicity and climate adversities. User adoption is transcendental, even if it requires efforts.