Di(2-pyridyl)ketone stabilized titanium dioxide nanoparticles for the room temperature processed electron transporting layer in organic photovoltaics

• Published in: Organic electronics Vol. 28; pp. 281 - 286
• Main Authors: Hwang, Heewon, Yoon, Soyeon, Seok, Jeesoo, Kim, Kyungkon
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2016
• Subjects: Charge recombination; Electron transporting layer; Interfacial layer; Polymer solar cells; Titanium dioxide nanoparticle; Interfacial layer; Charge recombination; Titanium dioxide nanoparticle; Polymer solar cells; Electron transporting layer
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2015.11.012

Monodisperse TiO2 nanoparticles are obtained through hydrolysis of titanium butoxide in the presence of di(2-pyridyl)ketone (DPK) and para-toluenesulfonic acid. The DPK ligand stabilized the surface of the TiO2 nanoparticle through complexation with TiO2. DPK stabilized TiO2 (TNP-DPK) can be dispersed without aggregation in alcoholic solutions at concentrations higher than 1 M. The synthesized particles have 4–5 nm size and spherical shape at amorphous phase. The atomic force microscope image reveals that only 0.1 wt% of TNP-DPK solution can form a conformal and dense film on top of the active layer. The TNP-DPK solution is used for an electron transporting layer (ETL) in organic photovoltaics (OPV) that utilizing poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th) as a photoactive layer. The power conversion efficiency of the OPV is significantly improved from 7.18% to 9.08% by inserting the TNP-DPK layer between photoactive layer and Al electrode. Based on the internal quantum efficiency and transient photo voltage experiments, the TNP-DPK layer is found to improve the charge collection efficiency and reduce the charge recombination at the active layer/electrode interface. These results clearly show that the solution processed TNP-DPK layer can play a role as an efficient ETL in OPVs. [Display omitted] •Di(2-pyridyl)ketone stabilized titanium dioxide nanoparticles were synthesized.•Synthesized nanoparticle was successfully introduced in polymer solar cells.•The device showed efficiency of 9.08% with reduced charge recombination.