A method for controlling the doping of flexible solar cells that leads to higher efficiencies is presented in Nature Communications this week. The results are promising for manufacturing low-cost photovoltaics with efficiencies of over 10%.
Thin-film flexible solar cells can be produced more cheaply for versatile applications than conventional bulk solar cells using materials such as silicon, although their efficiency is generally lower than non-flexible cells. Incorporating small amounts of other metals into these materials - a process known as doping - can help improve this, although the fabrication steps required can deteriorate their electronic properties. Now, Lukas Kranz and colleagues have succeeded in overcoming this obstacle in cadmium telluride (CdTe) solar cells doped with copper. They use vapour deposition and heat based treatments to carefully control the doping of copper atoms into the CdTe layer. When creating solar cell devices from these layers on glass substrates they achieve efficiencies of 13.6%, and 11.5% on metal substrates. These values exceed the threshold for industrialisation and demonstrate the feasibility of the approach for producing high-efficiency CdTe solar cells on flexible substrates. The method is promising for further improving the efficiency of CdTe photovoltaic devices.