Reported by Lin Zhang and Wei Ma

State Key Laboratory for Mechanical Behavior of Materials

Recently, nonfullerene organic solar cells have attracted enormous attention with the highest power conversion efficiency (PCE) of 13.1% and 14.9% for single junction device and tandem device, respectively. Even so, these progresses were achieved by spin-coating in small-area devices which is material consumptive and difficult to scale up to large-area. Fortunately, blade-coating serving as a prototype tool for slot-die coating can be very compatible with large-area roll-to-roll coating. In addition, the morphology of active layer, such as phase separation, phase purity, miscibility, crystallinity and crystallization orientation significantly affect the exciton generation, exciton dissociation, charge transfer and charge collection. Therefore, optimizing the morphology of active layer is of great importance for improving photovoltaic performance. However, optimizing morphology by using large-area coating method has not been reported yet. Besides, the common used high boiling point additives in optimization of morphology are difficult to remove, which affect the device stability. Therefore, it is better to use as few additives as possible in the fabrication of organic solar cells.

Under this circumstance, Ma group in XJTU fabricated non-fullerene solar cells in air by blade-coating which was assembled by themselves. Synchrotron radiation techniques of grazing incident wide-angle X-ray scattering (GIWAXS) and resonant soft X-ray scattering (RSoXS) were employed to investigate the morphology of active layer. It was found that blade-coating can induce a higher degree of molecular packing for both conjugated polymer donors and small-molecular acceptors. Thus, under the lower contents of high boiling point additives, higher photovoltaic performance and better device stability were achieved by blade-coating than the tranditional spin-coating, showing great potential in morphological optimization and large-area fabrication of organic solar cells.

The experiment was carried out by Lin Zhang and Prof. Wei Ma in State Key Laboratory for Mechanical Behavior of Materials. Recently, this work is published as an article entitled “Blade-Cast Nonfullerene Organic Solar Cells in Air with Excellent Morphology, Effciency, and Stability” on Advanced Materials, DOI: 10.1002/adma.201800343.

The paper is accessed by:

https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201800343

Group website: http://gr.xjtu.edu.cn/web/msewma/home