TY - JOUR
T1 - Picosecond luminescence approach to charge transfer in a tetraphenylporphyrin/SnO2 interface
AU - Suto, Shozo
AU - Yashima, Masataka
AU - Uchida, Wakio
AU - Goto, Takenari
N1 - Funding Information:
The authors would like to thank Dr. II. Kido of the Department of Chemistry,T ohoku University, for purification of the H,TPP powder. This work was partially supportedb y a Grant-in-Aids for Scientific Researchf rom the Ministry of Education, Sciencea nd Culture in Japan and by Takasago ResearchI nstitute.
PY - 1988/10/3
Y1 - 1988/10/3
N2 - The decay time of the luminescence from mono-molecular and excimer states in very thin tetraphenylporphyrin (H2TPP) films evaporated on SnO2 substrates has been measured in situ in a pressure of 2 × 10-6 Pa using a picosecond dye laser at 100 K. The decay time of the 665 nm luminescence in H 2TPP on a highly conductive SnO2 substrate (σ = 77 Ω-1 cm-1 is 800 ps in films with a thickness above 25 Å and decreases with decreasing thickness to 170 ps at 7.5 Å. Contrarily, the decay time for films on low conductive SnO2 (σ = 4.5 × 10-3 Ω-1 cm-1) is independent of film thickness. The luminescence quenching ratio calculated from the decay time coincides well with that from the relative luminescence intensity. This coincidence leads to the conclusion that luminescence quenching occurs through the mono-molecular excited state or the excimer state. We propose the following mechanism to explain these experimental results. First, a conduction electron of the highly conductive SnO2 substrate recombines with a hole of the H2TPP excimers resulting in a charge transfer state. Second, an electron is transferred from the excimer state of H2TPP to the conduction band.
AB - The decay time of the luminescence from mono-molecular and excimer states in very thin tetraphenylporphyrin (H2TPP) films evaporated on SnO2 substrates has been measured in situ in a pressure of 2 × 10-6 Pa using a picosecond dye laser at 100 K. The decay time of the 665 nm luminescence in H 2TPP on a highly conductive SnO2 substrate (σ = 77 Ω-1 cm-1 is 800 ps in films with a thickness above 25 Å and decreases with decreasing thickness to 170 ps at 7.5 Å. Contrarily, the decay time for films on low conductive SnO2 (σ = 4.5 × 10-3 Ω-1 cm-1) is independent of film thickness. The luminescence quenching ratio calculated from the decay time coincides well with that from the relative luminescence intensity. This coincidence leads to the conclusion that luminescence quenching occurs through the mono-molecular excited state or the excimer state. We propose the following mechanism to explain these experimental results. First, a conduction electron of the highly conductive SnO2 substrate recombines with a hole of the H2TPP excimers resulting in a charge transfer state. Second, an electron is transferred from the excimer state of H2TPP to the conduction band.
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U2 - 10.1016/0039-6028(88)90174-4
DO - 10.1016/0039-6028(88)90174-4
M3 - Article
AN - SCOPUS:4243600066
VL - 205
SP - 230
EP - 240
JO - Surface Science
JF - Surface Science
SN - 0039-6028
IS - 1-2
ER -