Modeling hydrogen inCuInSe2andCuInS2solar cell materials using implanted muons

Muon spin rotation experiments on ${\mathrm{CuInSe}}_2$ and ${\mathrm{CuInS}}_2$ were performed in the context of a study on the effect and behavior of hydrogen on chalcopyrite solar cell materials. The microscopic information delivered by implanted positive muons can be applied to the hydrogen case by analogy. It was found that the major fraction of the muons is in a diamagnetic environment but, at low temperatures, a fraction of 5–10 % has a paramagnetic surrounding. In ${\mathrm{CuInSe}}_2$ the site of the diamagnetic muon is tentatively assigned to the antibonding site close to Se and the onset of muon diffusion on a microsecond time scale is observed between 200 and 250 K. The pre-exponential factor for the hop rate and the activation energy are ${\nu }_0=3.4\mathrm{}\times {10}^{10}\hspace{0.5em}{\mathrm{s}}^{-1}$ and $E_a=220\mathrm{}$ meV. Above 250 K trapping occurs. The diffusion behavior in ${\mathrm{CuInS}}_2$ is similar, but the onset is shifted by 50 K to higher temperatures.