NUSOD Blog

Connecting Theory and Practice in Optoelectronics

NUSOD 2016 Preview: Modeling of light soaking effect in CdTe Solar Cells

light soakNearly all photovoltaic technologies exhibit changes in device performance under extended illumination, or “light soaking”. Experiments on both commercial modules and research cells based on CdTe technology have shown improvement of cell performance under light soaking conditions for up to 20 hours. Many accredited such phenomena to the passivation of traps and migration of Cu ions. In this work, we employed a self-consistent one-dimensional (1D) diffusion-reaction simulator to study the migration and passivation of Cu related dopants in CdTe solar cell as a function of soaking conditions.

device perfomance 2Our simulation shows that both passivation of Cu dopants and Cu ions migration under light soak could cause device performance enhancement. In our simulations, the passivation of Cu dopants contributes to 40% of the total performance change in less than 2 minutes of light soaking while the migration of Cu ions, a much slower process, is responsible for the rest 60% of performance changes. The simulation result also suggests that 10-12 – 10-13 cm2/s diffusivity of Cu interstitials could explain the 10-hour long light soaking effect at 65oC.

Full details of this work will be presented at the NUSOD 2016 conference in Sydney, Australia, talk WA2.

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