Details

Autor(en) / Beteiligte

• Correa, Roger S
• Santos, Bianca P. S
• Ribeiro, Arthur C
• da Silva, Luiz Alberto F
• Péan, Emmanuel V
• Davies, Matthew L
• Marques, Maria de Fátima V
• Rocco, Maria Luiza M

Titel

Spectroscopic study of D-A-D-A terpolymer films for optoelectronic applications

Ist Teil von

• Physical chemistry chemical physics : PCCP, 2022-07, Vol.24 (29), p.17852-17861

Erscheinungsjahr

2022

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Several strategies have been considered in search of more efficient organic materials for charge transfer in photovoltaic devices. Among them, the integration of donor-acceptor (D-A) functional units on a conjugated copolymer has been widely applied. In this framework, we evaluated four terpolymers made up of donor moieties derived from 9,9-dioctylfluorene and 9-(heptadecan-9-yl)-9 H -carbazole combined with 2,1,3-benzothiadiazole, the acceptor moiety, in different monomer ratios and polymerization routes (block and random microstructures). The preferred molecular orientation and charge transfer dynamics of the polymeric films were assessed by near edge X-ray absorption fine structure spectroscopy (NEXAFS) and resonant Auger electron spectroscopy (RAES) around the sulfur K-edge. Charge transfer times ( τ CT ) were estimated by the Core-Hole Clock (CHC) method. Films with a high degree of organization were identified for the block terpolymer and random terpolymers with uneven amounts of donor units, showing a preferred orientation of the benzothiadiazole (BT) molecular plane parallel to the substrate surface. The values of τ CT measured for all terpolymers were higher than those for typical polymers used in photovoltaic devices, which is not desirable for this type of optoelectronic application, but this may be correlated to the strong acceptor character of BT, the unit probed. To investigate the effect of film formation on the excited state behavior, steady-state and time-resolved photoluminescence measurements were also conducted. X-ray photoelectron spectroscopy (XPS) was employed to characterize the surface chemical composition of the terpolymer films. Based on the spectroscopic data the block copolymer appears to be the most suitable for the desired application. The preferential molecular orientation and charge transfer dynamics of four D 1 -A-D 2 -A terpolymers (three random and one block copolymer) with possible application in organic photovoltaic cells were investigated by spectroscopic techniques.