Tetra-indole core as a dual agent: a hole selective layer that passivates defects in perovskite solar cells†
An organic small molecule composed of a tetra-indole core was designed and introduced as a hole selective layer for the fabrication of perovskite solar cells (PSCs). 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 passivated the defects in perovskite by suppressing the non-radiative recombination as noted from photoluminescence and electrochemical impedance (EIS) measurements and gave improved photovoltaic performances. The device showed a power conversion efficiency of 15.83% when employed as an hole selective layer, however on passivating the interface of perovskite/hole selective layer, the PCE improved significantly to 19.23%. Additionally, the TTI treated device showed improved charge transfer behaviour and long-term stability when stored in the dark under an ambient atmosphere.