A universal Ti₃C₂ assisted strategy facilitates hole extraction of PEDOT:PSS anode interface layer for over 19% efficiency organic photovoltaics

Low hole extraction efficiency is a key factor restricting the performance of organic photovoltaic (OPVs). Improving the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and reduce its large extraction barrier with the active layer is viewed as an important direction to increase the hole extraction efficiency of OPVs. In this work, few-layer two-dimensional titanium carbide (Ti₃C₂) nanosheets were prepared by HCl/LiF etching and doped into PEDOT:PSS to fabricate OPVs devices. Ti₃C₂ nanosheets induced the configuration transformation of PEDOT from spiral benzoyl to linear quinone structure, form tightly packed large-size PEDOT nanocites, and connect these conductive nanocites to construct a new charge transport channel, thus boosting the conductivity of the PEDOT:PSS anode interface layer (AIL). In addition, Ti₃C₂ nanosheets adjusted the work function of PEDOT:PSS, thus decreasing the hole extraction barrier in OPVs. As 2% volume of Ti₃C₂ doping into PEDOT:PSS interlayer, the maximum power conversion efficiency (PCE) of PTzBI-oF:PYF-T-o, D18:L8-BO, as well as PM6:L8-BO based OPVs boosted from 15.61%, 17.92% and 15.49% to 16.83%, 19.05% and 17.33%, respectively. Our work can provide guidance for facilitating hole extraction of PEDOT:PSS, which is expected to contribute to the further progress of OPVs.