Effect of processing additive 1,8-octanedithiol on the lifetime of PCPDTBT based Organic Photovoltaics

• Degradation of PCPDTBT:PCBM OPVs is shown to increase with the inclusion of 1,8-octanedithiol (ODT).
• AFM scans indicate a greater change in the surface properties of devices fabricated with the ODT.
• An additional morphological change in the active layer during the light soaking is induced by ODT.

The effect that processing additives have upon the lifetime of PCPDTBT-based OPVs has been investigated. The results show conclusively that whilst ODT processing additive enhances the initial performance of PCPDTBT:PCBM OPVs, it is detrimental to their long term performance, when measured under light soaking at 1 Sun of irradiance. Results are shown for both encapsulated and non-encapsulated devices. Topographical and morphological measurements made using AFM and small- and wide-angle X-ray scattering of active layers show that there are greater morphological changes of devices fabricated with the 1,8-octanedithiol upon light soaking, revealing a relatively venerable morphology of the active layer processed with the additive, when subject to light soaking.

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