Realization of Large-Scale Polymer Solar Cells Using Ultrasonic Spray Technique Via Solvent Engineering

Reliability and reproducibility remain as main challenges in the realization of large-scale polymer solar cells. An easy and smart method to prototyping a high yield and large-scale PTB7:PC71BM solar cell is demonstrated by modified ultrasonic spray coating method, using a novel precursor solution containing a portion of a lower-toxicity trimethylbenzene. The formation of Marangoni-effect related defects such as coffee-rings and pin holes is successfully overcome via tuning the drying processes with optimization of the solvent ratio. XPS analysis confirms that the PTB7 enriched surface resulted in a vertical phase separated structure, and led to higher mobility of charge carriers to transport from the film to the buffer layer. The power conversion efficiency of the solar cell is improved to 8.23%. As well, the preparation of a large-scale active area solar cell of 18cm(2) with a maximum power output of 74.8mW is demonstrated promising for industrial applications.