Roll‐to‐Roll Sputter Coating of Aluminum Cathodes for Large‐Scale Fabrication of Organic Photovoltaic Devices

Abstract

We report the demonstration of sputter‐coated aluminum contacts directly onto P3HT:PCBM organic photovoltaic devices using a R2R process without detrimentally influencing the performance of the devices. The final sputtered devices do not require any protective buffer layers to produce efficient performance. Depth profiling analysis of sputtered films using X‐ray photoelectron spectroscopy (XPS) indicated the presence of a 5–6 nm insulating oxide layer generated at the cathode interface for all sputtering target power densities greater than 1.4 W cm−2. The aluminum penetration into the P3HT:PCBM film was found to be consistent with the depth of this oxide layer, suggesting that aluminum penetration into the organic film is not the primary reason for performance limitations in sputtered devices. Introduction of thermally evaporated aluminum buffer layers prior to deposition of sputtered aluminum cathodes demonstrated that the performance of devices after annealing matched those of reference devices prepared with no sputtering for a buffer layer thickness of only 20 nm. Further analysis of the device J‐‐V curves revealed an S‐shaped kink prior to annealing, indicating that the major reason for the poor performance in sputtered devices was the introduction of a charge extraction barrier at the cathode, which was subsequently removed upon annealing. Rigorous removal of oxygen from the sputtering chamber prior to aluminum deposition onto the P3HT:PCBM active layer was subsequently observed to produce a device with an efficiency close to that of the thermally evaporated reference device without the requirement for evaporated buffer layers. The results presented here highlight a pathway towards an alternative R2R cathode fabrication technique that allows the highly efficient aluminum cathodes employed in small‐scale devices to be transferred onto large‐scale, flexible, and low‐cost R2R printed organic electronic devices.

Roll‐to‐Roll Fabrication of Solution Processed Electronics

“…A research group from the University of Newcastle has demonstrated a pathway for ITO‐free fully R2R processed organic solar cells in a conventional geometry with a R2R sputtered aluminum top electrode . This shows that solution processable printing and coating methods can be combined with R2R vacuum techniques for the manufacturing of complete OPV modules …”

Perovskite Thin Film Synthesised from Sputtered Lead Sulphide

“…More complex structures, such as those used in the manufacture of highly efficient solar cells 37 , 38 , with the inclusion of mixed cations (Cs, MA and FA) and halides (I, Br), seem to be also feasible. Since sputtering is a very well-known technique for thin films deposition 39 – 43 , and its application on industrial scale 42 , 44 is already available in the market, this approach has potential to scale-up the perovskite solar cells production.…”

Printable Organic Semiconductors for Radiation Detection: From Fundamentals to Fabrication and Functionality

“…However, in terms of translating such technologies to large-scale fabrication, there has been substantially less work. Perhaps, most progress has been made in the arena of large-scale fabrication of printed organic photodiodes [15,33,105,116,[131][132][133][134][135][136][137][138][139][140][141][142][143][144][145][146][147][148][149] and field effect or electrochemically gated transistor devices [17,19,29,32,83,111,[150][151][152][153][154][155][156][157]. Each of these technologies provides a useful platform for the direct (transistors) or indirect (photodiode) detection of ionizing radiation using printed OSC technology, an area of research that is attracting increasing attention in recent years.…”