Metal-grid modeling and optimizations for organic solar cells

Abstract

In recent years, the efficiency of organic solar cells has been rapidly increasing, with lab-scale devices having crossed the point of 17% efficiency. However, large-area devices are still a step behind, only just recently crossing the 12% limit. One of the reasons for this observed lag is the finite conductivity of the transparent electrode used that introduces power loss. However, this problem can be solved by adding a metal grid to the transparent electrode to increase its conductivity. In this work, we studied, both theoretically and experimentally, the effect of a metal grid on the performance of organic solar cells. Specifically, we investigated cell performance as a function of the positioning and number of grid lines. Our results show that there is a characteristic cell length that depends on the cell's optoelectronic properties and the transparent electrode conductivity, and it enables prediction of an optimized number of grid lines for a given cell size. Moreover, it can be used to calculate the preferred position of the grid lines. Our findings of both the number and positioning of the grid lines can boost large-area cell efficiency even further and reduce the gap between large-area and lab-scale devices.