Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells

TLDR

Polymer solar cells have progressed, yet high efficiencies (>9%) remain limited to a few donor polymers and a single fullerene acceptor. The study aims to produce high‑efficiency thick‑film polymer solar cells across multiple polymer:fullerene pairs by creating an optimal morphology with crystalline yet small polymer domains. The morphology is governed by temperature‑dependent donor polymer aggregation, independent of fullerene type. The approach delivered efficiencies up to 10.8% with fill factors of 77%, and the derived aggregation rules produced three donor polymers exceeding 10% efficiency, offering greater design flexibility.

Abstract

Abstract Although the field of polymer solar cell has seen much progress in device performance in the past few years, several limitations are holding back its further development. For instance, current high-efficiency (>9.0%) cells are restricted to material combinations that are based on limited donor polymers and only one specific fullerene acceptor. Here we report the achievement of high-performance (efficiencies up to 10.8%, fill factors up to 77%) thick-film polymer solar cells for multiple polymer:fullerene combinations via the formation of a near-ideal polymer:fullerene morphology that contains highly crystalline yet reasonably small polymer domains. This morphology is controlled by the temperature-dependent aggregation behaviour of the donor polymers and is insensitive to the choice of fullerenes. The uncovered aggregation and design rules yield three high-efficiency (>10%) donor polymers and will allow further synthetic advances and matching of both the polymer and fullerene materials, potentially leading to significantly improved performance and increased design flexibility.