A non-fullerene acceptor with a diagnostic morphological handle for streamlined screening of donor materials in organic solar cells†
Utilizing the N-annulated PDI acceptor PDI–DPP–PDI, a simple air-processed and air-tested organic photovoltaic device fabrication procedure has been established to streamline the screening of donor materials. Post-deposition solvent vapour annealing of the active layer blend results in a preferential re-organization dictated by PDI–DPP–PDI and is responsible for significant increases in device performance. Employing this method, a series of low-cost and scalable donor polymers were screened to help select promising candidates as alternatives to the expensive high-performance donor polymer PTB7-Th. Universal improvements in performance upon solvent vapour annealing with a range of donor polymers highlighted the advantages of PDI–DPP–PDI and this post-deposition treatment. This facile screening protocol identified PDTT-BOBT as the most suitable PTB7-Th alternative in the surveyed series, with the best device efficiencies reaching 4.5% PCE compared to control devices with PTB7-Th at 4.6% PCE.