Prof Henry Snaith FRS

Abstract:

Organic semiconductors employed in solar cells are perfectly stable to solar irradiation provided oxygen content can be kept below 1 ppm. Paradoxically, the state-of-the-art molecular hole-transporter-based solid-state dye-sensitized solar cells only operate efficiently if measured in an atmosphere containing oxygen. Without oxygen, these devices rapidly lose photovoltage and photocurrent and are rendered useless. Clearly this peculiar requirement has detrimental implications to the long term stability of these devices. Through characterizing the solar cells in air and in oxygen-free atmospheres, and considering the device architecture, we identify that direct contact between the metallic cathode and the mesoporous metal oxide photo-anode is responsible for a shunting path through the device. This metal-metal oxide contact forms a Schottky barrier under ambient conditions and the barrier is suitably high so as to prevent significant shunting of the solar cells. However, under light absorption in an anaerobic atmosphere the barrier reduces significantly, opening a low resistance shunting path which dominates the current-voltage characteristics in the solar cell. By incorporating an extra interlayer of insulating mesoporous aluminum oxide, on top of the mesoporous semiconducting metal oxide electrode, we successfully block this shunting path and subsequently the devices operate efficiently in an oxygen-free atmosphere, enabling the possibility of long term stability of solid-state dye-sensitized solar cells.

Abstract:

We have fabricated infrared active hybrid solar cells composed of mesoporous SnO2 sensitized with PbS nanoparticles and infiltrated with organic hole-transporters, 2,2',7,7'-tetrakis(N,N-di-p-methoxypheny-amine)-9,9'-spirobifluorene(spiro-OMeTAD) or poly(3-hexylthiophene). We observe photo-action to 1100nm, peak quantum-efficiency over 20%, open-circuit voltages up to 0.5V and power conversion efficiencies of over 0.5% under simulated sun light. As compared to solar cells composed of mesoporous TiO2 sensitized with the same PbS nanoparticles, the SnO2 based devices generate 4 times the photocurrent density under simulated sun light. © 2011.

Abstract:

We present an investigation into incorporating core-shell Au-SiO 2 nanoparticles into dye-sensitized solar cells. We demonstrate plasmon-enhanced light absorption, photocurrent, and efficiency for both iodide/triiodide electrolyte based and solid-state dye-sensitized solar cells. Our spectroscopic investigation indicates that plasmon-enhanced photocarrier generation competes well with plasmons oscillation damping with in the first tens of femtoseconds following light absorption. © 2010 American Chemical Society.

Abstract:

We present an investigation into incorporating core-shell Au-SiO(2) nanoparticles into dye-sensitized solar cells. We demonstrate plasmon-enhanced light absorption, photocurrent, and efficiency for both iodide/triiodide electrolyte based and solid-state dye-sensitized solar cells. Our spectroscopic investigation indicates that plasmon-enhanced photocarrier generation competes well with plasmons oscillation damping with in the first tens of femtoseconds following light absorption.