Probing the Electronic Structure of a Photoexcited Solar Cell Dye with Transient X-ray Absorption Spectroscopy.
This study uses transient X-ray absorption (XA) spectroscopy and time-dependent density functional theory (TD-DFT) to directly visualize the charge density around the metal atom and the surrounding ligands following an ultrafast metal-to-ligand charge-transfer (MLCT) process in the widely used Ru(II) solar cell dye, Ru(dcbpy)2(NCS)2 (termed N3). We measure the Ru L-edge XA spectra of the singlet ground ((1)A1) and the transient triplet ((3)MLCT) excited state of N3(4-) and perform TD-DFT calculations of 2p core-level excitations, which identify a unique spectral signature of the electron density on the NCS ligands. We find that the Ru 2p, Ru eg, and NCS π* orbitals are stabilized by 2.0, 1.0, and 0.6 eV, respectively, in the transient (3)MLCT state of the dye. These results highlight the role of the NCS ligands in governing the oxidation state of the Ru center.
†Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
Benjamin E
BE
Van Kuiken
‡Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Nils
N
Huse
‡Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Hana
H
Cho
‡Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Matthew L
ML
Strader
†Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
Michael S
MS
Lynch
‡Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Robert W
RW
Schoenlein
†Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
Munira
M
Khalil
charge transfer; core-level excitation; excited states; transient X-ray absorption