H2O induced structural modification of pentacene crystal

Water is one of the obstacles for prolonged life-time of organic based field-effect-transistors (OFETs). Here, we show how H2O molecules adsorb and affect pentacene crystal by using photoelectron spectroscopic methods. Diffusion into the crystal is accompanied with accumulation of H2O onto the crystal. Valence band, core level, and X-ray absorption spectra show that H2O molecules physisorb on the pentacene surface via oxygen, resulting in the increase of the hole-injection barrier. The diffused molecules results in the deteriorated crystallinity, and they reflect the weakening inter-molecular interactions of pentacene crystal.