In this study, a newly-synthesized polymer, viz. benzoic acid endcapped poly(silolodithiophene) is evaluated as a potential photosensitizer in solar cell device applications. The steady-state absorption and photoluminescence spectra were recorded to understand the excited-state properties of the polymer when dissolved in chlorobenzene. A set of four mesoporous TiO2-coated, fluorine-doped tin oxide conductive substrates were dipped for 18 hours in the polymer solution for its adsorption onto the TiO2 surface. The excited state decay dynamics of the polymer, both dissolved in chlorobenzene and on TiO2 films with different electrolyte concentrations, were studied using femtosecond transient/pump-probe spectroscopy (fs-TAS). An ultrafast laser amplifier system, Astrella (7 mJ @ 800 nm, 1 kHz repetition rate) and a HELIOS FIRE transient absorption spectrometer were used to perform the fs-TAS measurements. Carriers were generated by exciting the samples at 560 nm and decay was monitored in both visible and near-IR wavelength regions. A significant difference in the relaxation processes was observed when comparing the polymer samples in solution and when incorporated into devices. A slow ground state bleach (~20 ps), as well as slower recoveries, were exhibited by the polymer molecules in solution. This observation could be attributed to reorganization of the excited state into a charge-separated form before decaying to the ground state. In devices, however, the ground state bleach was observed to be much shorter (~1 ps) with very fast recoveries, suggesting fast electron injection and fast recombination.

Electron injection efficiency studies of polymer sensitized devices by transient absorption spectroscopy for solar cell applications

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.