Prof Henry Snaith FRS

Abstract:

We present a spiro-linked molecule 2,2',7,7'-tetrakis(3-hexyl-5-(7-(4-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)-9,9'-spirobifluorene which acts as a secondary absorber in solid-state excitonic solar cells. Blending with a hole-transporting material 2,2'7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene and used in conjunction with a near-infrared dye (termed TT1) results in an extended spectral response which yields a notable increase in short-circuit current and power conversion efficiency. This enhancement is due to both exciton energy transfer and also nanoscale charge generation in the blend via the formation of an excited state spiro-complex with charge transfer character.

Abstract:

Dye-sensitized solar cells are composed of mesostructured electron transporting electrodes, typically fabricated from metal oxides. These electrodes are sensitized with a light absorbing dye and filled with a redox active electrolyte or hole-transporter. There has been considerable interest in solid-state DSCs and hybrid solar cells which use a molecular hole-transporter or light absorbing semiconducting polymer in place of the corrosive redox active electrolyte typically employed. Highest reported efficiencies for solid-state DSC are around 5%, and two major aspects of this device require significant improvement for this to be increased to values greater than the electrolyte based counterpart (c.a. 12%). The first is to enhance the light absorption in the active layer. The second is to improve the conversion of absorbed photons to collected charge. The nano to meso-structure of the metal oxide electrodes critically influences the end performance of the solar cell. Diblock copolymers exhibit well defined morphological structures on the nano to meso scale. Typical phases of interest for photovoltaic applications are the cylindrical phase or the 3D gyroid morphology. Replicating these morphologies into electronically active materials can be done a number of ways --a one-pot synthesis, where the block copolymer acts as a structure-directing agent for a semiconductor precursor, or a sequential templating process where one of the phases of a structured polymer film is removed and replaced with a semiconductor. We converted well-defined diblock copolymer structures into anataze TiO2 both ways and incorporated these films into solid-state DSCs. By comparing both cylindrical and the bi-continuous double gyroyd phases, we present the benefits and disadvantages of 1D vs 3D nanostructures in this solar cell.

Abstract:

Dye-sensitized solar cells are composed of mesostructured electron transporting electrodes, typically fabricated from metal oxides. These electrodes are sensitized with a light absorbing dye and filled with a redox active electrolyte or hole-transporter. There has been considerable interest in solid-state DSCs and hybrid solar cells which use a molecular hole-transporter or light absorbing semiconducting polymer in place of the corrosive redox active electrolyte typically employed. Highest reported efficiencies for solid-state DSC are around 5%, and two major aspects of this device require significant improvement for this to be increased to values greater than the electrolyte based counterpart (c.a. 12%). The first is to enhance the light absorption in the active layer. The second is to improve the conversion of absorbed photons to collected charge. The nano to meso-structure of the metal oxide electrodes critically influences the end performance of the solar cell. Diblock copolymers exhibit well defined morphological structures on the nano to meso scale. Typical phases of interest for photovoltaic applications are the cylindrical phase or the 3D gyroid morphology. Replicating these morphologies into electronically active materials can be done a number of ways --a one-pot synthesis, where the block copolymer acts as a structure-directing agent for a semiconductor precursor, or a sequential templating process where one of the phases of a structured polymer film is removed and replaced with a semiconductor. We converted well-defined diblock copolymer structures into anataze TiO both ways and incorporated these films into solid-state DSCs. By comparing both cylindrical and the bi-continuous double gyroyd phases, we present the benefits and disadvantages of 1D vs 3D nanostructures in this solar cell. 2