In the present work, Cu2ZnSnS4 (known as kesterite) nanoparticles were synthesized by two-phase method. X-ray diffraction measurement confirmed formation of kesterite crystalline phase. Size of nanoparticles in colloidal suspension was determined by dynamic light scattering method and it was 9.2 +/- 2.5 nm. The obtained nanoparticles were used as inorganic hole-transporting material (HTM) in paintable carbon-based PSC (C-PSC). Power conversion efficiency (PCE) was increased from 6.1% +/- 1.1% for HTM-free paintable C-PSC to 9.3% +/- 0.9% for paintable C-PSC with kesterite HTM. This significant increase in PCE was due to the higher hole-extraction rate at carbon counter-electrode, in the presence of kesterite HTM, which was confirmed by different measurement methods such as incident photon to current conversion efficiency, photoluminescence spectroscopy and electrochemical impedance spectroscopy. Although hot-injection synthesized kesterite nanoparticles have been previously used as inorganic HTM in Ag and Au-based PSCs, using kesterite nanoparticles, synthesized by a cheaper method, i.e. two-phase method, in C-PSCs was reported in the present work, for the first time.