Studies of trapped holes in reduced oxygen and water condition

SUK, JUNGDON; PALACIOS, RODRIGO E.; FAN, FU-REN F.; GREY, JOHN K.; BARD, ALLEN J.; BARBARA, PAUL F.

New Orleans, LA, EE.UU

Congreso; The 235th ACS National Meeting; 2008

The American Chemical Society

Deeply trapping of charges is an important issue in the application of plastic semiconductors. The trapped charges affect the functioning of devices by shifting the turn on bias in transistors and modifying conversion efficiencies in solar cells and light-emitting displays. Deeply trapped holes can be caused by defects in semiconductor material or introduced impurities such as water and oxygen which encourage charge trapping. In this work we use Single-molecule spectro-electrochemistry (SMS-EC) to study the energetics dynamics of deep traps in individual nanoparticles of the conjugated polymer poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). The experiments were carried out in inside a glovebox controlled environment where oxygen and water concentrations were less 5 and 1 ppm, respectively. Under these conditions the fluorescence of individual nanoparticles showed a slow recovery component (after bias induced charging) which is associated with the presence of deep traps. These results are qualitatively similar to those from experiments carried out in ambient conditions, suggesting that water and oxygen do not play a significant role in the observed slow fluorescence recovery phenomena. This observation reinforces the idea that deep traps can be formed by a charge-induced chemical reaction in conjugated polymers.