Improved photovoltaic response of a near-infrared sensitive solar cell by a morphology-controlling seed layer

• A 5 nm annealed seed layer of ClInPc induces triclinic phase across the entire film.
• The triclinic phase of ClInPc introduce new absorption feature in the NIR region.
• The triclinic phase of ClInPc improves solar cell overall performance.

We demonstrate that a thin seed layer of indium phthalocyanine chloride (ClInPc) annealed under mild conditions effectively controls the morphology of both post-annealing deposited ClInPc films and ClInPc:C60 mixed films, introducing the triclinic phase into the commonly monoclinic phase dominating film. ClInPc/C60 planar solar cells and ClInPc:C60 (1:1) planar-mixed solar cells with and without the triclinic phase were studied. Increased short circuit current (Jsc), fill factor (FF), external quantum efficiency (EQE) and internal quantum efficiency (IQE) of the devices containing triclinic phase is attributed to the enhanced absorption in the near infrared (NIR) region and decreased series resistance. The correlation between open circuit voltage (Voc) and dark saturation pre-exponential factor (Jso) was analyzed to investigate Voc loss upon annealing. The overall performance of device is considerably improved by introducing the triclinic phase of ClInPc.

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