TUTCRIS - Tampereen teknillinen yliopisto


Electron and energy transfer in five different size quantum dots (QD) and phthalocyanine (Pc) hybrids.



OtsikkoPhotoinduced Hole Transfer in QD-Phthalocyanine Hybrids-MRS fall meeting
JulkaisupaikkaMRS fall meeting, Boston, USA
TilaJulkaistu - 30 marraskuuta 2015
OKM-julkaisutyyppiD3 Artikkeli ammatillisessa konferenssijulkaisussa


In the present work, electron and energy transfer in five different size Quantum dots and Pthalocyanine hybrids are studied. Quantum Dots(QDs) of five sizes with diameter in the range 2.8-5.3 nm were employed.
Organic -semiconductor hybrids have attracted significant scientific attention after the invention of the quantum dots [1]. A combination of QDs and phthalocyanine offer interesting component structures. The absorption and emission of QDs as well as the other optical properties also depend on the size. Absorption spectra of QD-Pc show Pc aggregation for 3 or more Pc per each QD. Adding different concentration of Pc from 1 Pc per 1 QD to 10 Pc per 1 QD caused quenching of the QD emission although the position and shape of the band remain the same. This behavior indicates electron or energy transfer between QD and Pc [2].
Time-correlated single photon counting (TCSPC) was used to find the lifetimes of the pure QD and Pc samples, and QD-Pc hybrid. The excitation wavelength was 483 nm for all hybrid samples which means QDs are excited. The TCSPC measurements show reduction of the emission lifetime by adding Pc to QDs. It is in agreement with QD emission quench by adding Pc. Pump-probe method was also used to investigate electron and energy transfer in QD-Pc (1:7) hybrids. The concentration of Pc was high enough to cause at least 60% quenching of the QD emission in QD-Pc complex, typically QD:Pc = 1:7, although absorption spectra showed Pc aggregation in such a high concentration of Pc. There was no change in absorption spectrum of the samples after the measurements, indicating high photo-stability [3]. Excitation wavelength was 480 nm. The results show the average time constant of band formation at 650 nm is larger for larger QDs. On the other hand, the overlap of emission spectra QDs with absorption spectra of Pc is larger for larger QDs rather than smaller one. The combination of the transient absorption measurement results and absorption and emission spectra measurement indicate electron transfer between QD and Pc.