The improvement of inverted perovskite solar cells by the introduction of CTAB into PEDOT:PSS

The power conversion efficiency (PCE) reported for the inverted perovskite solar cells (PSCs) is still less than that of the regular structure, and low open circuit voltage (V oc ) is one of the crucial problems for achieving high PCE in inverted PSCs. In this study, a new modification strategy was developed by doping poly (3,4-ethylenedioxythiophene)-poly-(styrene sulfonate) (PEDOT: PSS) with the cetyl trimethyl ammonium bromide (CTAB) to passivate the bottom of perovskite layer and enhance properties of PEDOT:PSS. The work function of PEDOT: PSS was altered from −4.18 to −4.21 eV, the Fermi level of CTAB-doped PEDOT:PSS better fitted to the valence band of perovskite layer, thereby leading to a higher build-in voltage. As a result, the V oc increased by 70 mV, up to 0.90 V and the PCE of the device increased from 10.21% to 12.53%. Furthermore, the device based on CTAB-doped PEDOT:PSS still retained over 75% of the initial PCE after exposing the device in the ambient condition (20–40% humidity, 10–30 ℃) for 30 days.