P3HT-Based Solar Cells: Structural Properties and Photovoltaic Performance

Each year we are bombarded with B.Sc. and Ph.D. applications from students that want to improve the world. They have learned that their future depends on changing the type of fuel we use and that solar energy is our future. The hope and energy of these young people will transform future energy technologies, but it will not happen quickly. Organic photovoltaic devices are easy to sketch, but the materials, processing steps, and ways of measuring the properties of the materials are very complicated. It is not trivial to make a systematic measurement that will change the way other research groups think or practice. In approaching this chapter, we thought about what a new researcher would need to know about organic photovoltaic devices and materials in order to have a good start in the subject. Then, we simplified that to focus on what a new researcher would need to know about poly-3-hexylthiophene:phenyl-C61-butyric acid methyl ester blends (P3HT: PCBM) to make research progress with these materials. This chapter is by no means authoritative or a compendium of all things on P3HT:PCBM. We have selected to explain how the sample fabrication techniques lead to control of morphology and structural features and how these morphological features have specific optical and electronic consequences for organic photovoltaic device applications

Evidence for exciton quenching by hole polarons in thick P3HT:PCBM solar cells

\u3cp\u3eLoss mechanisms near each of the two electrodes of semitransparent solar cells with ZnO and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) contacts are investigated as function of the thickness of the photoactive poly(3-hexylthiophene) : methanofullerene (P3HT:PCBM) bulk heterojunction layer (200-500 nm). Varying the intensity of the illumination through the ZnO contact indicates that bimolecular recombination is an important loss mechanism. Illumination through the PEDOT:PSS contact reveals a loss mechanism that is independent of light intensity. Photoluminescence measurements demonstrate that primary P3HT excitons can be quenched by charge carriers that diffuse into the active layer from the PEDOT:PSS contact.\u3c/p\u3

Influence of photon excess energy on charge carrier dynamics in a polymer-fullerene solar cell

Optical excitation of a polymer-fullerene solar cell via the charge-transfer transition at the donor-acceptor interface, leads to generation of charge carriers displaying dynamics that are indistinguishable from those generated by excitation of the conjugated polymer at higher photon energy. This indicates that excess energy liberated in the photoinduced electron transfer between polymer and fullerene is not essential for the charge carrier generation