|The figure above illustrates intermediate electron states within the zinc tellurium band gap introduced by the addition of oxygen atoms to the alloy. The figure on the right shows electrons in the material that are available to conduct electricity. Image credit: Lin-Wang Wang.
Today’s typical solar panel converts between seven and 17 percent of sunlight into electricity – a far cry from the 28 percent efficiency of fossil fuel generators. To make matters worse, because the initial cost of solar panels is so high, generating electricity with solar panels is typically three to four times as expensive as buying it from the local power company.
Solar panels generate electricity when they absorb the sun’s heat. The heat causes electrons to jump from the valence level, where they are locked in place, to the conduction band, where they can move freely and carry a current. If the sunlight that’s hitting the panel has energy too low to boost electrons to the conduction band, the solar panel can’t convert that sunlight into electricity.
The researchers investigating the zinc tellurium oxide are hoping that the oxygen in the material will introduce an intermediate energy level – much like a landing on a staircase – that can absorb smaller amounts of energy. If they are right, adding the oxygen to zinc telluride solar cells will increase the efficiency from 30 percent to 60 percent.
To reach that goal, the researchers are using supercomputers at Oak Ridge National Laboratory, the National Energy Research Scientific Computing Center and Lawrence Berkeley National Laboratory.
The first step is to submit a simulation job to one of the machines to which they have access. Their job goes in a queue of waiting computations. It can take a day or two to get to the front of the line, but when they do, the job only takes a few hours because the machines are so powerful.
“We look at the result, check its scientific meaning, do some analysis and try to understand the result,” said Wang. “Then we resubmit another job which is related to the first job but modifying some aspects, maybe checking some other aspects of the problem.”
Even if the alloy turns out to be too expensive for mass manufacture, the simulations will have accomplished something important. “This is really the first of its kind,” said Wang. “The hope is that if it can be worked out and prove the concept, then we can try other systems with more banded elements.”
—Miriam Boon, iSGTW