Techniques involving the use of high-intensity, shortduration light pulses were applied to the study of the kinetics of photoconductivity in films of metal-free phthalocyanine. These experiments, in conjunction with measurements of steady-state photoconductivity indicate that the principal route for the formation of charge carriers is via the first excited singlet state of phthalocyanine, although the lowest triplet stats can to some extent contribute to changecarrier production. Consistent with a variety of steadystate and kinetic conductivity measurements, a mechanism is proposed for the ionization of the excited states of phthalocyanine to form charge carriers. This mechanism is strongly supported by the studies of the effects of electron acceptors and donors on the electrical properties of phthalocyanine. A method was developed to measure the diffusivity and mobility of the majority charge carrier. Such measurements lead to a room-tempenature value of approximately 10/sup -3/ cm/ sup 2/v-sec for the mobility of positive-charge carriers (holes) in phthalocyanine. An interpretation of the kinetics of flash-photoconductivity decay suggested that the mobility of charge carriers is concentration-dependent, being lower at high carrier concentration. The decay of the photocurrent is suggested to be the result of a diffusionlimited bimolecular recombination of electrons and holes, with a recombination radius of approximatsly one molecular diameter. (auth).

Explore an authoritative resource with coverage of foundational concepts of photoconductivity and photoconductive materials In Photoconductivity and Photoconductive Materials, Professor Kasap delivers a definitive guide to the basic principles of photoconductivity and a selection of present topical photoconductive materials. Divided into two parts, the set begins with basic concepts and definitions and coverage of characterization using steady state, transient and modulated photoconductivity techniques, including the novel charge extraction by linearly increasing voltage (CELIV) method The physics of terahertz photoconductivity and fundamentals of organic semiconductors lsois are also covered. Part Two of the set starts with a comprehensive review of a wide range of photoconductive materials and then focuses on some of the most important photoconductors, including hydrogenated amorphous silicon, cadmium mercury telluride, various x-ray photoconductors, diamond films, metal halide perovskites, nanowires and quantum dots. Photoconductive antenna application is also included. Filled with contributions from leading authors in the field, this book also offers: A thorough introduction to the characterization of semiconductors from photoconductivity techniques, including uniform illumination and photocarrier grating techniques Comprehensive explorations of organic photoconductors, including photogeneration, transport, and applications in printing Practical discussions of time-of-flight transient photoconductivity, including experimental techniques and interpretation In-depth examinations of transient photoconductivity of organic semiconducting films and novel transient photoconductivity techniques Perfect for research physicists, materials scientists, and electrical engineers, Photoconductivity and Photoconductive Materials is also an indispensable resource for postgraduate and senior undergraduate students working in the area of optoelectronic materials, as well as researchers working in industry.