Effect of solvent additive in an organic solar cell by spontaneous spreading process

Abstract

Spontaneous spreading (SS) process is a coating process that forms organic film using Marangoni effect and transfer the film. The degradation by oxygen is small in the films coated by the SS process because of low oxygen penetration. Also, the SS process is able to be applied to roll to roll process which is a continuous process. Additionally, it is possible to make stacked structure device without damage of the bottom film even using same solvent at the top and bottom layer. However, multi-solvent has to be often used to suppress shrink of film during the SS process. Herein, using small amount of solvent additive as multi-solvent, I study the morphology of films from the SS process. I confirmed that solvent additive remains very long during the SS process because of slow dry, leading to over-aggregation. As the over-aggregation was suppressed, adjusting the solvent additive ratio enable to control molecular orientation of morphology. In result, I reach PCE 11.4% of an organic solar cell.