Improving the efficiency of a solar panel is very tricky work as currently researchers are happy to achieve even a tenth of a percent increase. Ultimately though, these increases have a limit to solar cells without altering their design, but in the 1960s a way was proposed to get around this limit. Finally, after fifty years researchers at MIT have created a proof-of-concept solar cell that may be able to step around the Shockley-Queisser, or SQ limit.
The SQ limit states that a single junction solar cell, like the typical silicon solar cell, cannot convert the energy of a photon to a voltage more efficiently than roughly 34%. There are some ways around this though, such as concentrating the light and increasing the amount of time light spends within the photovoltaic material. What was suggested in the 1960s though was the addition of a material that has the ability to excite two electrons with a photon, instead of just one. Only now has one of these materials, pentacene, been successfully incorporated into a solar cell. Without the pentacene, the energy not transferred to an electron would be lost as waste heat.
Being a proof-of-concept though, the solar cell only has a 2% efficiency rating, but now that they know it works, the MIT researchers and others will be working to optimize the system and push as high as they can.