Towards High‐Throughput Coating and Printing of Light‐Emitting Electrochemical Cells: A Review and Cost Analysis of Current and Future Methods

Abstract A revolution is ongoing in the field of artificial light emission, with two prime examples being the quickly growing application of the energy‐efficient light‐emitting diode (LED) in illumination and the introduction of the high‐contrast organic LED (OLED) display in various handheld appliances. It is anticipated that the next big breakthrough will constitute the emergence of a true low‐cost technology, which features novel and attractive form factors such as flexibility, light‐weight, and large‐area emission. To realize this challenging vision, it is mandatory to identify an emissive technology that can be fabricated in a low‐energy and material‐conservative manner. In this context, recent demonstrations of a roll‐to‐roll (R2R) compatible coating and printing of thin‐film light‐emitting electrochemical cells (LECs) on flexible substrates are highly interesting. Here, we review these achievements, and perform a first analysis of the merits of different LEC fabrication methods with regard to material consumption, capital investment, running cost, and throughput. Among our findings we mention a fault‐tolerant, small‐volume batch fabrication of LEC devices using spray sintering, which can be executed at a low installment cost of 100 000 €, but where the large‐area devices currently carry a fabrication cost tag of 14 000 € m −2 . The true appeal of the technology is, therefore, better visualized in the high‐volume R2R‐coating scenario, for which the installment cost is 20 times higher, but where the projected price tag is much more attractive (11 € per m 2 ). If such flexible and light‐weight (and potentially metal‐free) sheets are driven at a luminance of 1000 cd m −2 , the cost per lumen is a mere 0.0036 € lm −1 , which is one order of magnitude lower than the projected future costs for LEDs and OLEDs.