Prof Henry Snaith FRS

Abstract:

A series of conjugated 3-hexylthiophene derivatives with a cyanoacrylic acid group has been prepared with conjugation length from one up to five thiophene units (1T-5T). The UV-vis spectra, photoluminescence spectra, electrochemical data and DFT calculations show lowering of LUMO energies and red-shift of absorption into the visible as the thiophene chain length increases. TiO2/P3HT solar cells were prepared with prior functionalization of the TiO2 surface by 1T-5T and studies include cells using undoped P3HT and using P3HT doped with H-TFSI. Without H-TFSI doping, photocurrent generation occurs from both the oligothiophene and P3HT. Doping the P3HT with H-TFSI quenches photocurrent generation from excitation of P3HT, but enables very effective charge extraction upon excitation of the oligothiophene. In this case, photocurrent generation increases with the light harvesting ability of 1T-5T leading to a highest efficiency of 2.32% using 5T. Overall, we have shown that P3HT can act in either charge generation or in charge collection, but does not effectively perform both functions simultaneously, and this illustrates a central challenge in the further development of TiO2/P3HT solar cells.

Abstract:

(Chemical Equation Presented) Organic dyes for solid-state sensitized solar cells are commonly prepared by combining an electron-withdrawing group (acceptor, A) on one side of a conjugated π-spacer and one or more electrondonating groups (donor, D) on the other side. It is shown that without an electron donor group a signifi cantly higher opencircuit voltage is achieved, while maintaining the short-circuit current.