Interface Engineering of Perovskite/Hole Transport Layer Using Nano‐Network Formation in Small Molecule–Polymer Blend for Efficient Inverted Perovskite Solar Cells

Abstract Interface engineering is critical for reducing trap states present in various device interfaces and improving the efficiency of perovskite solar cells (PSCs). This study introduces the blending effect of poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) into metal‐phthalocyanine−tetrasulfonated acid tetrasodium salt (TS‐MPc) used as a hole transport layer (HTL) in organic–inorganic hybrid PSCs. PEDOT:PSS with a low pH induces the self‐assembly and formation of mesh‐like nano‐networks in a TS‐MPc layer, which is confirmed by atomic force microscopy and elemental mapping using energy‐dispersive spectroscopy. Compared with pure TS‐MPc, nano‐networked TS‐MPc with PEDOT:PSS exhibits higher crystallinity by grazing‐incidence wide‐angle X‐ray scattering. The nano‐network formation contributes to ≈30% enhancement in the power conversion efficiency (14.65%) of device with PEDOT:PSS‐assisted TS‐CuPc as HTL, compared with device using conventional PEDOT:PSS (11.02%). In addition, the device with PEDOT:PSS‐assisted TS‐MPc shows a significant improvement in stability owing to the reduced pH of the HTL compared with the device using pristine PEDOT:PSS.