Flexible Transparent Self Adhesive Electrode Enabling the Scale up of High Efficiency Perovskite Solar Cells
Cecile Charbonneau a, Matthew Carnie a, Peter Greenwood a, Matthew Davies a, Daniel Bryant a, David Worsley a, Trystan Watson a
a SPECIFIC, Swansea University, Baglan Bay Innovation and Knowledge Centre, Baglan, SA12 7AX, United Kingdom
International Conference on Hybrid and Organic Photovoltaics
Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Ecublens, Switzerland, 2014 May 11th - 14th
Organizers: Michael Graetzel and Mohammad Nazeeruddin
Oral, David Worsley, presentation 220
Publication date: 1st March 2014

The field of thin film hybrid organic inorganic photovoltaics has been recently reinvigorated by the  development of solid state organolead halide perovskite solar cells [1,2] achieving over 15% performance at lab-scale [3]. Attention is now starting to turn to the manufacturing processes required to scale these lab devices into modules, for high volume output roll to roll processing on low cost substrates such as metal foils and plastic sheeting

To enable the manufacture of a metal mounted perovskites we have begun to address a number challenges. Firstly, in order to create a reliable and conformal TiO2 charge injection / blocking layer we have developed a novel doctor blade coating which avoids the requirement for either spin coating or multiple pass spray pyrolysis and can be cured in seconds with near infrared radiation (NIR). This not only allows charge injection on perovskite devices but prevents unwanted back reactions for other solid state third generation HOPV. The second challenge we will present in this paper is that of application of the active layer. We have developed a new coating method in which inert nano-particles are incorporated that act as sites for nucleation and allow for a dense perovskite film to be created with very few of the defects that reduce cell efficiency. In addition, this can be applied without spin coating using an air blade and cured using NIR in a matter of seconds allowing for rapid throughput. Thirdly in laboratory devices, charge collection at the counter electrode is achieved via sputtering or evaporating of an opaque metallic contact, typically gold or silver. This is entirely unsuitable for metal devices where light penetration is required through the counter electrode and adds significant cost to any other device. We have developed a unique dual purpose transparent contact providing conductivity, hole extraction and mechanical adhesion. This new system is a blend of an acrylic emulsion pressure sensitive adhesive (PSA) with a very low loading (0.018 volume fraction) PEDOT:PSS. This creates a dual phase polymer to be formed which is not only transparent (~80%) and conductive but also adhesive in nature. This is combined with a PET top sheet material that incorporates nickel grids providing extremely high conductivity (1.2 Ω□). In assembled cells (1 cm2) this has identical performance levels to evaporated contacts (up to 9.8% efficiency) and we have also used it to assemble larger 10 cm2 cells (at 6%).


Figure 1. (a) SEM micrograph of a transparent conducting laminate applied to an embedded Ni grid on PET (b) Photo of the laminate applied to a steel substrate. Performance levels of this flexible contact are similar to that of an opaque evaporated metal.
[1] Kim, H-S.; Lee, C-R.; Im, J-H.; Lee, K-B.; Moehl, T.; Marchioro, A.; Moon, S-J.; Humphry-Baker, R.; Yum, J-H.; Moser, J.E.; Grätzel, M.; Park, N-G. Lead Iodide Perovskite sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%, Scientific Reports 2012, 2, 1–7. [2] Lee, M.M.; Teuscher, J.; Miyasaka, T.; Murakami, T.N.; Snaith, H.J. Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites, Science. 2012, 338, 643–7. [3] Liu, M.; Johnston, M.B.; Snaith, H.J. Efficient planar heterojunction perovskite solar cells by vapour deposition, Nature. 2013, 501, 395–8.
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