The move marks a critical milestone in developing efficient solar cells which can directly compete with electricity generated by conventional energy sources. It is also expected to reduce electricity cost.
Researchers from the NREL collaborated with Washington State University (WSU) and the University of Tennessee to improved cell voltage by placing phosphorus atoms on tellurium lattice.
The team then carefully formed ideal interfaces between materials with different atomic spacing to complete the solar cell, thus improving cell’s conductivity and carrier lifetime each by orders of magnitude
The new approach allowed the researchers to fabricate the CdTe solar cells with an open-circuit voltage, breaking the 1-volt barrier for the first time, overcoming a practical limit that has been pursued till date.
Researchers improved cell voltage by shifting their focus away from a standard processing step using cadmium chloride.
CdTe solar cells could become a low-cost alternative to silicon solar cells which represent 90% of the solar cell market.
WSU’s School of Mechanical and Materials Engineering and Department of Physics Regents professor Kelvin Lynn said: "It’s a significant milestone. It’s been below 900 millivolts for decades. A low-cost alternative, the CdTe solar cells have the lowest carbon footprint and can be adapted better than silicon in conditions including hot, humid weather and low light."
The crystals were grown using a technique called melt growth, which allows precise control over purity and composition. Researchers then synthesize the crystal in a furnace above 1100°C and cool it from the bottom up at a rate of about one millimeter per hour.
Lynn added: "Others have tried dopants, but they didn’t have the control and purity that we have. And the purity matters."
The project is being backed by the US Energy Department’s SunShot Initiative. The program is intended to make solar cost-competitive with traditional energy sources.
Recently, First Solar has announced it has achieved 22.1% conversion efficiency for the CdTe PV research cell, marking a new world record.
The new efficiency has been certified at the Newport Corporation’s Technology and Applications Center (TAC) PV Lab.
Image: WSU’s Kelvin Lynn with crystals made in his lab. Photo: courtesy of WSU Photo Services.
