Interface Electronic States of Epitaxially Grown C<sub>60</sub> on Dinaphtho[2,3-<i>b</i>:2′,3′-<i>f</i>]thieno[3,2-<i>b</i>]thiophene Single Crystals

Electronic states formed at the interfaces of molecular semiconductor materials in organic optoelectronic devices are essential for their functionality. However, resolving these states at the complex and disordered interfaces of practical devices is challenging. In this study, the electronic states at well-defined molecular semiconductor p–n heterojunctions formed by epitaxial growth of C60 on single-crystals of dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) were characterized by X-ray photoelectron spectroscopy and photoelectron yield spectroscopy. Our observations revealed the formation of interfacial electronic states and band bending on both sides of the heterojunction, suggesting electron transfer from DNTT to C60. Notably, these features were not revolved for conventional disordered interfaces formed on vacuum-deposited thin-films of DNTT.