Inverted ITO- and PEDOT:PSS-free polymer solar cells with high power conversion efficiency

• Published in: Solar energy materials and solar cells Vol. 117; pp. 98 - 102
• Main Authors: Kohlstädt, Markus, Grein, Maria, Reinecke, Patrick, Kroyer, Thomas, Zimmermann, Birger, Würfel, Uli
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2013; Elsevier
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Energy; Exact sciences and technology; Inverted; ITO-free; Natural energy; Organic solar cell; PEDOT:PSS-free; Photoelectric conversion; Photovoltaic conversion; PTB7; Solar cells. Photoelectrochemical cells; Solar energy; Thin metal layer; Thin metal layer; PEDOT:PSS-free; PTB7; Inverted; Organic solar cell; ITO-free; Industrial production; Stacking; Conversion rate; Bearing(mechanics); Organic solar cells; Thin film; Tin addition; Sheet resistivity; Thiophene derivative polymer; Energy conversion; Zinc oxide; ITO layers; Cost lowering; Heterojunction; Production process; Aluminium oxide; Polymer blends; Aluminium addition; Indium oxide; Solar cell; Silver; High power; Manufacturing process; Flexible structure; High efficiency; Styrenesulfonate polymer; Compatibility; Transparent material
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2013.05.023

Highest published power conversion efficiencies of organic solar cells have mostly been achieved on substrates bearing a transparent indium tin oxide (ITO) electrode. However, the incorporation of ITO is not suited for future industrial production processes of organic solar cells, which will rely on a high-throughput of flexible substrates in order to achieve low cost of the final product. In this manuscript we present an alternative transparent electrode consisting of a layer stack of aluminum doped zinc oxide and a thin silver layer. Substrates with these electrodes have a transparency of above 75% in the wavelength range in which the photoactive layer absorbs light. Solar cells with a bulk-heterojunction of PTB7 and PC71BM in an inverted device architecture achieved a power conversion efficiency of 6.1%, which is the highest reported value for polymer solar cells free from both ITO and PEDOT:PSS. The sheet resistance of the novel electrodes increased only marginally after repeated bending which shows their full compatibility with future reel-to-reel processes or flexible products. [Display omitted] •Inverted polymer cells free from ITO and PEDOT:PSS are presented.•ITO is replaced by a thin layer stack of silver and aluminum doped zinc oxide.•ITO-free electrodes show low sheet resistance and high transparency.•Efficiencies of 6.1% were achieved for solar cells without ITO and PEDOT:PSS.•Bending tests prove applicability of ITO-free electrodes in R2R-processes.