In this study, we have synthesized a solution-processable phenothiazine, 4-phenothiazin-10-yl-anisole (APS), as hole collection material in organic solar cells (OSCs). The APS reveals unique optical and electronic properties which can efficiently modify the work function (ΦW) of indium tin oxide (ITO) electrode to enhance the electron blocking capability. Moreover, the results indicate that the APS is highly air-stable which can significantly enhance the long-term stability of OCSs. The inverted device based on APS reached a power conversion efficiency (PCE) of 3.56% and exhibited much better stability under ambient conditions relative to that of the corresponding PEDOT:PSS based device.