Observation of singlet exciton photoionization in anthracene single crystal at 2.95 eV

✍ Scribed by Ryuzi Katoh; Masahiro Kotani

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 399 KB
• Volume: 166
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(90)80026-a

✦ Synopsis

Photo-carrier generation with 420 nm light (hv=2.95 eV) in an anthracene single crystal has been studied, The main experimental results are the following: ( 1) The photocurrent waveforms correspond to the penetration depth of the exciting light. (2) The number of carriers generated is proportional to I& and becomes proportional to I:!' under strong excitation. ( 3) The photocurrent has a temperature dependence different from that of the absorption coefftcient of the ground state. These observations indicate that charge carriers are generated through photoionization of a singlet exciton, i.e. by sequential two-step excitation. With an applied electric field of 1.5~ IO" V cm-', the cross section of the singlet exciton photoionization (with I.=420 nm) is 7 x 1O-'9 cm2. The Onsager length r,, determined from the temperature dependence of the photocurrent, is 36 A.