Charge polarization in annealed bulk-heterojunction solar cells

• Published in: Thin solid films 2008-08, Vol.516 (20), p.7230-7233
• Main Authors: Sliaužys, G., Juška, G., Genevičius, K., Arlauskas, K., Dennler, G., Österbacka, R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Charge transfer; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electrical properties of specific thin films; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Energy; Exact sciences and technology; Materials science; Nanoscale materials and structures: fabrication and characterization; Natural energy; Organic semiconductors; Other topics in nanoscale materials and structures; Photovoltaic conversion; Physics; Quantum wells; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2007.12.039

By annealing bulk-heterojunction solar cells made from blends of regioregular poly(3-hexylthiophene) (RR-PHT) and 1-(3-methoxycarbonylpropyl)-1-phenyl-[6,6] C 61 (PCBM) the quantum efficiency as well as charge carrier mobilities increases, while the bimolecular recombination coefficient decreases. We clarify the capacitance and conductivity properties of both annealed and non-annealed cells using the charge carrier extraction by linearly increasing voltage (CELIV) technique. We found that the capacitance in the annealed samples is a strong function of temperature, while the non-annealed samples show only the geometrical capacitance. The results can be explained by the demixing of the PCBM and RR-PHT and formation of high conductivity regions in the blend after the annealing process.