Scientists from the National Renewable Energy Laboratory (NREL) have created a world record six-junction solar cell that has a conversion efficiency of 47.1%. The device is built using III-V materials which are known for a wide range of light-absorbing properties. Total the device contains 140 layers of III-V materials, with each layer design to capture a specific part of the solar spectrum.
These types of solar cells are typically used to power satellites because of there high efficiency and cost. Here on earth, the six-junction solar cell is best suited for concentrator solar panels. This type of panels cut the cost down quite a bit since you only need a fraction of the material used in conventional solar panels. Also, the efficiency increases as you concentrate the light.
The next step for the scientist is to exceed the 50% barrier and significantly reduce the cost so that these solar cells can reach new markets.