  Carbazole-based self-assembled monolayers (PACz-SAMs), anchored via their
phosphonic acid group on a transparent conductive oxide (TCO) have demonstrated
excellent performance as hole-selective layers in inverted perovskite solar
cells. However, the influence of the TCO microstructure on the work function
(WF) shift after SAM anchoring as well as the WF variations at the
micro/nanoscale have not been extensively studied yet. Herein, we investigate
the effect of the Sn-doped In2O3 (ITO) microstructure on the WF distribution
upon 2PACz-SAMs and NiOx/2PACz-SAMs application. For this, ITO substrates with
amorphous and polycrystalline (featuring either nanoscale or microscale-sized
grains) microstructures are studied. A correlation between the ITO grain
orientation and 2PACz-SAMs local potential distribution was found via Kelvin
probe force microscopy and electron backscatter diffraction. These variations
vanish for amorphous ITO or when adding an amorphous NiOx buffer layer, where a
homogeneous surface potential distribution is mapped. Ultraviolet photoelectron
spectroscopy confirmed the ITO WF increase after 2PACz-SAMs deposition.
Considering the importance of polycrystalline TCOs as high mobility and
broadband transparent electrodes, we provide insights to ensure uniform WF
distribution upon application of hole transport SAMs, which is critical towards
enhanced device performance.
