title: In-depth analysis of chloride treatments for thin-film CdTe solar cells.
abstract: CdTe thin-film solar cells are now the main industrially established alternative to silicon-based photovoltaics. These cells remain reliant on the so-called chloride activation step in order to achieve high conversion efficiencies. Here, by comparison of effective and ineffective chloride treatments, we show the main role of the chloride process to be the modification of grain boundaries through chlorine accumulation, which leads an increase in the carrier lifetime. It is also demonstrated that while improvements in fill factor and short circuit current may be achieved through use of the ineffective chlorides, or indeed simple air annealing, voltage improvement is linked directly to chlorine incorporation at the grain boundaries. This suggests that focus on improved or more controlled grain boundary treatments may provide a route to achieving higher cell voltages and thus efficiencies.
authors: Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, UK.
authors: J D
authors: JD
authors: Major
authors: Department of Physics, Umm Al-Qura University, KSA, Mecca Al Taif Road, Mecca 24382, Saudi Arabia.
authors: M
authors: M
authors: Al Turkestani
authors: Department of Physics, G.J. Russell Microscopy Facility, Durham University, South Road, Durham DH1 3LE, UK.
authors: L
authors: L
authors: Bowen
authors: University of Southampton, School of Physics &Astronomy, Southampton, Hants SO17 1BJ, UK.|Centre for Photonics and Quantum Materials, Skolkovo Institute of Science and Technology, Moscow 143026, Russia.
authors: M
authors: M
authors: Brossard
authors: Materials Science and Technology Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, Tennessee 37831, USA.
authors: C
authors: C
authors: Li
authors: University of Southampton, School of Physics &Astronomy, Southampton, Hants SO17 1BJ, UK.|Centre for Photonics and Quantum Materials, Skolkovo Institute of Science and Technology, Moscow 143026, Russia.
authors: P
authors: 0000-0002-3557-5299
authors: P
authors: Lagoudakis
authors: Department of Materials Science and Engineering, National University of Singapore, Singapore 117576, Singapore.
authors: S J
authors: SJ
authors: Pennycook
authors: Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, UK.
authors: L J
authors: LJ
authors: Phillips
authors: Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, UK.
authors: R E
authors: RE
authors: Treharne
authors: Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool L69 7ZF, UK.
authors: K
authors: K
authors: Durose