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

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 100000Euro, but where the large-area devices currently carry a fabrication cost tag of 14000Eurom(-2). The true appeal of the technology is, therefore, better visualized in the high-volume R2R-coating scenario, for which the installment cost is 20times higher, but where the projected price tag is much more attractive (11Euro per m(2)). If such flexible and light-weight (and potentially metal-free) sheets are driven at a luminance of 1000cdm(-2), the cost per lumen is a mere 0.0036Eurolm(-1), which is one order of magnitude lower than the projected future costs for LEDs and OLEDs.