Researchers at the UK's Loughborough University have found what they call as the 'missing piece' of the fact that chlorine treatment helps improve power conversion efficiency of cadmium telluride (CdTe) solar modules. They are now looking doping CdTe with other elements to push for over 25% efficiency.
Their research work focuses on how and why chlorine improves efficiency by deploying quantum mechanical methods. For a reference range, they explain that untreated CdTe has very low efficiency of about only 1%. Once treated with cadmium chlorine at 420 ºC for 20 minutes, the efficiency jumps up drastically. Currently, the highest conversion efficiency for CdTe modules is 22.1%, achieved by the most prominent CdTe module manufacturer First Solar, Inc. of the US back in 2016 (see Making Up To The Milestone).
While it is known that chlorine treatment helps with stacking faults, through the process of passivation chlorine is able to deactivate some of the traps for electrons, created by grain boundaries and make these less active, thereby increasing the efficiency of CdTe. The team emphasized that the missing piece was understanding how the stacking faults disappear.
Disappearance of stacking faults signals that CdTe cell is going to have good performance. "This has never been shown before," explained team member Dr. Pooja Goddard.
Complete paper by the research team has been published in the Nature Communications magazine that's available for free viewing under the title Chlorine activated stacking fault removal mechanism in thin film CdTe solar cells: the missing piece.
Speaking of higher efficiencies for solar modules, TaiyangNews is organizing a 1-day Reliable PV Module Design Conference on August 31, 2021 where presenters will discuss the importance of long term reliability of PV modules at a time when technological breakthroughs are leading to better performances for solar modules. Registrations to the event are free and can be done here.