Organic small molecule composed of tetra-indole core was designed and introduced as hole selective layer for perovskite solar cells (PSCs) fabrication. 5,10,15,20-tetrahydrotriindole[2’,3’:4:2’,3’:5,6:2’,3’:7,8]cycloocta[1,2-b]indole (TTI) when integrated in PSCs, also passivate the defects in perovskite by suppressing the non-radiative recombination as noted from photoluminescence and electrochemical impedance (EIS) measurements and gave improve photovoltaic performances. The device showed a power conversion efficiency of 15.83% when employed as an HTM, however on passivating the interface of perovskite/HTL, the PCE improved significantly to 19.23%. Additionally, the TTI treated device showed improved charge transfer behaviour and long-term stability when store in dark under ambient atmosphere.