Impact of Device Polarity on the Photovoltaic Performance of Polymer Solar Cells
Mengmeng Li a, Martijn Wienk a, Rene Janssen a
a Molecular Materials and Nanosystems, Eindhoven University of Technology, Netherlands, Netherlands
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV18)
Benidorm, Spain, 2018 May 28th - 31st
Organizers: Emilio Palomares and Rene Janssen
Oral, Mengmeng Li, presentation 133
DOI: https://doi.org/10.29363/nanoge.hopv.2018.133
Publication date: 21st February 2018

The impact of device polarity on the photovoltaic performance is still under debate, although the inverted (n-i-p) device structure has become more popular than the conventional (p-i-n) configuration. It has been proposed that the use of acidic poly(ethylenedioxy­thiophene):poly(styrene sulfonate) (PEDOT:PSS) and reactive metals such as Al in the conventional device configuration cause issues regarding the device stability and performance, and that inverted devices are capable of enhancing the optical electric field and improving the interfacial contact. However, a one-to-one comparison for high-efficiency polymer solar cells has been rarely reported, which blurs our understanding of the intrinsic role of the device polarity on the power conversion efficiency (PCE).

In this contribution, we have evaluated five diketopyrrolopyrrole (DPP) based polymers with various chemical structures, including alkyl chains on the DPP units and backbones, and molecular weights, and demonstrated that the polymer solubility has a crucial role on the optimal device polarity. For polymers with good solubility, inverted devices showed a 10-25% improvement in photovoltaic performance compared to conventional one. In contrast, identical PCEs are observed for less soluble polymers, independent of device polarity. Additionally, the optimization of cosolvent and use of retroreflective foil efficiently boost the performance of DPP polymer solar cells, with PCE approaching 10%.

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