L. Jay Guo and coworkers from the University of Michigan introduce a new route to polymer solar cell processing that allows evaporation of solvent through surface encapsulation and induced alignment (ESSENCIAL) of polymer chains by applied pressure. Utilizing the popular bulk heterojunction concept, their ESSENCIAL polymer solar cells exhibit percent conversion efficiencies comparable to that of those fabricated on rigid substrates by thermal or solvent-assisted annealing methods.

Their approach, which is able to control parameters such as film thickness and uniformity even on a roll coating set-up, leads to an optimized morphology and better distribution and crystallinity of the components, which cannot be achieved by conventional methods. Their best roll-to-roll devices are up to 3.5% efficient, even without a PEDOT:PSS layer that is used in lab-scale preparation of this polymer cell. The ESSENCIAL method is also applicable to high-speed, dynamic processes.

The advantages of the ESSENCIAL method to induce optimal polymer solar cell morphology in a short processing time pave the way for scalable high-efficiency polymer solar cell fabrication. The authors believe that this process is a potential manufacturing technique for other bulk heterojunction materials that have exhibited higher efficiencies, therefore it permits realization of high-efficiency polymer solar cells using a high-speed roll-to-roll process.

H. J. Park et al., Adv. Mater. ; DOI: 10.1002/adma.201000250