Cosensitized Porphyrin System for High-Performance Solar Cells with TOF-SIMS Analysis

Wenjun Wu; Huaide Xiang; Wei Fan; Jinglin Wang; Haifeng Wang; Xin Hua; Zhaohui Wang; Yitao Long; He Tian; Wei-Hong Zhu

doi:10.1021/acsami.7b00281

Cosensitized Porphyrin System for High-Performance Solar Cells with TOF-SIMS Analysis

ACS Appl Mater Interfaces. 2017 May 17;9(19):16081-16090. doi: 10.1021/acsami.7b00281. Epub 2017 May 2.

Authors

Wenjun Wu¹, Huaide Xiang¹, Wei Fan², Jinglin Wang¹, Haifeng Wang¹, Xin Hua¹, Zhaohui Wang², Yitao Long¹, He Tian¹, Wei-Hong Zhu¹

Affiliations

¹ Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Centre for Computational Chemistry, Shanghai Key Laboratory of Functional Materials Chemistry, School of Chemistry and Molecular Engineering, East China University of Science and Technology , Shanghai 200237, China.
² Key Laboratory of Organic Solids, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.

PMID: 28425293
DOI: 10.1021/acsami.7b00281

Abstract

To date, development of organic sensitizers has been predominately focused on light harvesting, highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels, and the electron transferring process. In contrast, their adsorption mode as well as the dynamic loading behavior onto nanoporous TiO₂ is rarely considered. Herein, we have employed the time-of-flight secondary ion mass spectrometry (TOF-SIMS) to gain insight into the competitive dye adsorption mode and kinetics in the cosensitized porphyrin system. Using novel porphyrin dye FW-1 and D-A-π-A featured dye WS-5, the different bond-breaking mode in TOF-SIMS and dynamic dye-loading amount during the coadsorption process are well-compared with two different anchoring groups, such as benzoic acid and cyanoacrylic acid. With the bombardment mode in TOF-SIMS spectra, we have speculated that the cyano group grafts onto nanoporous TiO₂ as tridentate binding for the common anchoring unit of cyanoacrylic acid and confirmed it through extensive first-principles density functional theory calculation by anchoring either the carboxyl or cyano group, which shows that the cyano group can efficiently participate in the adsorption of the WS-5 molecule onto the TiO₂ nanocrystal. The grafting reinforcement interaction between the cyano group and TiO₂ in WS-5 can well-explain the rapid adsorption characteristics. A strong coordinate bond between the lone pair of electrons on the nitrogen or oxygen atom and the Lewis acid sites of TiO₂ can increase electron injection efficiencies with respect to those from the bond between the benzoic acid group and the Brønsted acid sites of the TiO₂ surface. Upon optimization of the coadsorption process with dye WS-5, the photoelectric conversion efficiency based on porphyrin dye FW-1 is increased from 6.14 to 9.72%. The study on the adsorption dynamics of organic sensitizers with TOF-SIMS analysis might provide a new venue for improvement of cosensitized solar cells.

Keywords: Solar cells; TOF-SIMS; cosensitization; organic sensitizes; photovoltaics.