Conjugated Polymer Photovoltaic Cells

TLDR

Conjugated polymers are attractive photovoltaic semiconductors because they strongly absorb light and can be deposited on flexible, low‑cost substrates, yet single‑polymer cells are inefficient due to limited exciton splitting, which can be improved by interfaces between semiconductors with offset energy levels. The authors aim to achieve efficiencies above 10 % by optimizing cell architecture for efficient exciton splitting and charge transport and by narrowing the polymer band gap to absorb more of the solar spectrum. Their strategy involves architectural optimization and band‑gap reduction to promote efficient exciton splitting and charge transport. Blending polymers with electron‑accepting materials such as C60 derivatives, cadmium selenide, and titanium dioxide has yielded power conversion efficiencies of nearly 4 %.

Abstract

Conjugated polymers are attractive semiconductors for photovoltaic cells because they are strong absorbers and can be deposited on flexible substrates at low cost. Cells made with a single polymer and two electrodes tend to be inefficient because the photogenerated excitons are usually not split by the built-in electric field, which arises from differences in the electrode work functions. The efficiency can be increased by splitting the excitons at an interface between two semiconductors with offset energy levels. Power conversion efficiencies of almost 4% have been achieved by blending polymers with electron-accepting materials such as C60 derivatives, cadmium selenide, and titanium dioxide. We predict that efficiencies higher than 10% can be achieved by optimizing the cell's architecture to promote efficient exciton splitting and charge transport and by reducing the band gap of the polymer so that a larger fraction of the solar spectrum can be absorbed.