Photocarrier Generation Efficiency of Pyrromethene-Doped Polymers

Abstract

Solid-state dye lasers based on polymethylmethacrylate (PMMA) polymers and pyrromethene laser dyes are currently being evaluated for lasing yield, damage threshold, and device lifetime.1 The fluorescence pathway in these solid-state dyes competes with the carrier production path. Popovic2 has demonstrated the connection between fluorescence yield and carrier generation for the phthalocyanines, namely higher fluorescence yield correlates with lower carrier yield. An improved understanding of the mechanism of organic photoconductors may enable selective optimization of conditions for lasing (fluorescence) or photocarrier production. Since pyrromethene dyes are known to exhibit strong fluorescence under zero field conditions3, low photocarrier yield and thus a high activation barrier for carrier production is predicted. The objective of this study is to determine the activation energy of photocarrier production in laser excited pyrromethene/PMMA samples by measuring the temperature dependence of the photoresponse. The dependence of charge generation on electron donor dopants, dye concentration, and laser intensity are also investigated; consequently information on charge traps and thermal decomposition rates is obtained.