PERIODIC MULTILAYERS OF PERYLENE-3,49,10-TETRACARBOXYLIC DIANHYDRIDE AND CHLOROINDIUM PHTHALOCYANINE - LIMITATIONS TO LONG-TERM STABILITY

The linear optical properties of periodic ultrathin multilayers of per ylene-3,4:9,10-tetracarboxylic dianhydride (PTCDA) and chloroindium ph thalocyanine (ClInPc) change after exposure to ambient environments. T his discoloration extends over a period of months. The B- and Q-bands of ClInPc decrease significantly in intensity, while the PTCDA absorba nce spectra are unchanged. ClInPc and PTCDA multilayers alone are stab le in air over the same period of time. UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS) are in agreement with a destruction o f the Pc chromophore. This reaction may be initiated by reaction of th e anhydride groups of PTCDA with ambient moisture, forming carboxylic acids, as seen by XPS. Control experiments show that PTCDA hydrolyzes in the presence of water and that ClInPc degrades if exposed to acids. These results impact the device implications for long-term use of PTC DA/phthalocyanine assemblies.