Recently, inorganic nanoparticles have been studied as hole transporting materials (HTM) in perovskite solar cells (PSCs). Inorganic HTMs are believed to provide better stability compared to conventional organic HTMs, such as spiro-OMeTAD. One of the challenges of nanoparticle HTMs is the high density of defects at the interface with the perovskite film, which reduces the device's fill factor. In this study, we use N, N '-di (naphthalene-1-yl)-N, N ' diphenyl benzidine (NPB) small molecules to passivate the surface of perovskite films in carbon-based PSCs with CuInS2 nanoparticles as the HTM. By applying NPB, trap density decreases from 1.35 x 10(16) cm(-3) to 5.09 x 10(15) cm(-3). NPB interface passivation results in a power conversion efficiency (PCE) of 16.11% compared to the control device with PCE of 14.92% in carbon-based perovskite solar cells. Moreover, improved contact angle was obtained for NPB surface-treated film (61.9 degrees) compared to the reference film (40.6 degrees), providing better protection against moisture induced degradation. The surface-treated devices maintained 92% of their efficiency after 4000 h of storage at ambient condition, while the control device showed a rapid and notable degradation, losing >58% of the initial efficiency under the same condition.