The field of organic solar cells (OSCs) continues to grow rapidly as new non-fullerene small molecule acceptors are created to boost device efficiencies above 13% and with 15% in sight. The commercialization of nonfullerene OSCs relies critically on the response and lifetime under typical operating conditions (for instance, temperature, humidity) and the ability of scale-up fabrication in the cheapest and most benign way possible. Realizing high efficiency in printed nonfullerene OSCs via scalable materials and less toxic solvents remains a grand challenge,  a challenge that is now timely to address as OSC efficiency in research devices has improved so much. 

In order to continue advancing scalable printing, our group explored chlorine-free, in air blade-coating for fabricating high performance OSCs. We have also been able to quantify the molecular packing, complex morphology, drying dynamics, and key device performance metrics of the blade-coated polymer:fullerene[1] and polymer:polymer[2] OSCs with the use of advanced X-ray scattering and in-situ spectroscopic ellipsometry tools. Using this scalable coating method, we are able to achieve an efficiency of nearly 11%[3] with a new photoactive combination FTAZ:IT-M, despite processing in air with a humidity of ~50%. More importantly, these blade-coated FTAZ:IT-M devices are very stable against high-temperature (150 °C) heating and using aged solution stored up to 20 days in air shows only a small performance loss. Together, the new material system and approach yield the highest reported performance for nonfullerene OSC devices by a coating technique approximating scalable fabrication methods. The quantitative relations and associated insights can aid in the future development of low-cost, low-toxicity, and high-stability non-fullerene OSCs that highly adhere to environmental and health safety regulations to decrease the energy losses and improve device efficiency. Our results also imply that these nonfullerene OSCs have the potential to catch up with perovskites in performance without the stability and toxicity issues.