Highly pure pentacene crystals grown by physical vapor transport: the critical role of the carrier gas

The impurities in commercial pentacene products prohibit systematic and accurate studies on pentacene. We report that highly pure pentacene crystals can be obtained in high yield by using a physical vapor transport process with hydrogen (H2) carrier gas. While other popular carrier gases including argon and nitrogen gas result in dihydropentacene–pentacene cocrystals as a major product, only H2 carrier gas results in pure pentacene crystals. This happens by effectively suppressing the disproportionation reaction of pentacene, which largely owes to its reaction with dihydropentacene, a popular impurity in pentacene. The efficient formation of highly pure pentacene crystals directly from commercial raw precursors will contribute to systematic studies on pentacene as well as development of novel strategies for the growth of high purity organic semiconducting materials.