Thicker, efficient polymer-based solar cells

November 20, 2017

What is the scientific achievement?

The columnar structure enhances charge mobility in the organic materials, and allows devices to be fabricated more than three times thicker than usual and maintain  their performance.

CFN Users from Stony Brook University, working with CFN scientists, demonstrated that adding a third polymer component to the traditional binary mixture of organic solar cell components facilitates self-assembly of a columnar architecture that improves performance.

Why does this achievement matter?

This ternary blend organic solar cell architecture has potential to enable reliable, large-area manufacturing because the devices can be made at thicknesses better suited for conventional coating processes.

What are the details?

Polymer-based solar cell enlarge

Illustration of a tertiary blend polymer-based solar cell, showing polymer (pink plates) and fullerene (grey spheres) active components, and a third polymer (dark grey columns) that promotes self-assembly of efficient, columnar charge collection pathways (green arrows).

Low-cost, large-area scalability by solution processing is an important advantage of polymer organic solar cells. Typical organic solar cells, however, have active layer thicknesses of less than 100 nanometers, for optimal device efficiency due to the limitations of polymer semiconductor carrier mobility.  This presents a significant challenge for solution-based manufacturing — large-area coating technologies, (e.g., roll-to-roll or slot-die coatings) are unable to provide reliable films at such thin dimensions.  In this work, the team found that adding a tertiary polymer phase to the binary blend of organic solar cell materials leads to a self-assembled columnar nanostructure, which enhances the charge mobility and photovoltaic performance in devices with layer thicknesses of more than 300 nanometers — which is more than three times thicker than typical. Detailed experimental studies and simulations reveal that surface tension between the polymeric components is crucial for obtaining the self-assembled columnar nanoarchitecture that provides efficient charge extraction pathways. Practically, this ternary blend organic solar cell architecture has potential to enable reliable large-area manufacturing because the devices can be made at thicknesses better suited for conventional coating.

CFN Capabilities:

CFN Materials Synthesis facilities were used to fabricate and characterize the organic solar cells.

Publication Reference

H. Li, Z. Yang, C. Pan, S.K. Satija, D. Xu, D. Gersappe, C.-Y. Nam†, M.H. Rafailovich†, “A new strategy to engineer polymer bulk heterojunction solar cells with thick active layers via self-assembly of tertiary columnar phase,” Nanoscale 9, 11511 (2017).

DOI:  10.1039/C7NR03789A

Acknowledgement of Support

This research was supported in part by NSF-1344267 program. This research was in part carried out at the Center for Functional Nanomaterials (CFN) of Brookhaven National Laboratory (BNL), which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-SC0012704.

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