Slot-Die and Roll-to-Roll Processed Single Junction Organic Photovoltaic Cells with the Highest Efficiency

The record efficiency of the state-of-the-art polymer solar cells (PSCs) is rapidly increasing, due to the discovery of high-performance photoactive donor and acceptor materials. However, strong questions remain as to whether such high-efficiency PSCs can be produced by scalable processes. This paper reports a high power conversion efficiency (PCE) of 13.5% achieved with single-junction ternary PSCs based on PTB7-Th, PC₇₁BM, and COi8DFIC fabricated by slot-die coating, which shows the highest PCE ever reported in PSCs fabricated by a scalable process. To understand the origin of the high performance of the slot-die coated device, slot-die coated photoactive films and devices are systematically investigated. These results indicate that the good performance of the slot-die PSCs can be due to a favorable molecule-structure and film-morphology change by introducing 1,8-diiodooctane and heat treatment, which can lead to improved charge transport with reduced carrier recombination. The optimized condition is then used for the fabrication of large-area modules and also for roll-to-roll fabrication. The slot-die coated module with 30 cm² active-area and roll-to-roll produced flexible PSC has shown 8.6% and 9.6%, respectively. These efficiencies are the highest in each category and demonstrate the strong potential of the slot-die coated ternary system for commercial applications.