Polymer Photovoltaic Cells with Rhenium Oxide as Anode Interlayer

Area of Science:

• Materials Science
• Renewable Energy
• Organic Electronics

Background:

• Polymer solar cells (PSCs) offer a promising renewable energy source.
• Regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) are common active layer materials.
• Interfacial layers are crucial for optimizing charge transport and device performance in PSCs.

Purpose of the Study:

• To investigate the effect of rhenium oxide (ReO3) as a buffer layer on the performance of P3HT:PCBM based polymer solar cells.
• To understand the influence of ReO3 layer thickness on the electrical characteristics of these solar cells.
• To explore the mechanism behind the observed decrease in device performance.

Main Methods:

• Fabrication of polymer solar cells using P3HT:PCBM active layers and ReO3 buffer layers.
• Characterization of electrical properties, including open-circuit voltage (Voc).
• X-ray photoelectron spectroscopy (XPS) to analyze ReO3 oxidation states.
• Kelvin Probe measurements to determine the work function of the ReO3 layer.

Main Results:

• Insertion of a ReO3 interfacial layer led to decreased performance in P3HT:PCBM solar cells.
• XPS analysis indicated ReO3 decomposition during thermal evaporation.
• Kelvin Probe measurements revealed a work function of 5.13 eV for evaporated ReO3.
• The decomposition resulted in a lower work function buffer layer, creating a higher energy barrier between ITO and the active layer.

Conclusions:

• Rhenium oxide is not a suitable buffer layer material for P3HT:PCBM polymer solar cells due to performance degradation.
• ReO3 decomposition during thermal evaporation is the primary cause of reduced device efficiency.
• The formation of a higher energy barrier at the ITO/active layer interface impedes charge extraction.