Understanding Printed Hexagonal Contacts for Large Area Solar Cells through Simulation and Experiments

Since their conception, organic electronic semiconductors have promised large area optoelectronic devices that can be mass produced at a fraction of the cost and embodied energy of devices made from traditional semiconductors. However, upscaling from small area lab-scale fabrication techniques to large area roll-to-roll (R2R) production has proved a substantial challenge. At the heart of this upscaling problem is the need for low cost, reliable contacts which can be readily printed. Device performance is often limited by the contacts, in terms of charge extraction efficiency and morphological compatibility of the sequentially deposited layers. Herein, high-speed R2R flexographic and gravure printing are combined with numerical device modeling to understand the performance of printed silver hexagonal contacts, and how contact design can affect final device performance. A strategy is presented which we dub "virtual upscaling" whereby the performance of the printed contact is virtually evaluated with an active layer material/device structure before the full device stack is printed. Through this methodology, a set of general design rules is developed which can be applied when experimentally optimizing contacts of optoelectronic devices. This approach has the potential to significantly reduce the number of design iterations and thus print runs when upscaling a structure.