Photovoltaic Performance,\nOptical Current Loss Simulation,\nand Conductive Atomic Force Microscopy Analysis of Organic Solar Cells\nBased on PM6:Y7

In this work, an investigation of the photovoltaic (PV)\nperformance\nof organic solar cells (OSCs) based on PM6:Y7, in combination with\na conductive atomic force microscopy (c-AFM) study, is presented.\nOSCs were fabricated and tested under regular atmospheric conditions,\nemploying the conventional structure glass/ITO/PEDOT:PSS/PM6:Y7/PFN/Field’s\nmetal (FM) where FM, a eutectic alloy of Bi, In, and Sn, served as\nan alternative top electrode, deposited easily via drop casting at\n95 °C, eliminating the requirement of a high-vacuum chamber.\nAn optimum active film thickness of 72 nm is identified for the PV\ndevices, reaching a power conversion efficiency (PCE) of 11.44 ±\n0.22% (best PCE = 11.76%). Further, optical constants (<i>n</i> and <i>k</i>) were determined for PEDOT:PSS, PM6:Y7, and\nPFN films via modeling of transmittance data; these parameters were\nused to simulate the external quantum efficiency response, which provided\nthe optical performance-limiting factors across all cell layers and\ninterfaces within the OSC. Likewise, topography measurements showed\nthat the 72 nm-thick PM6:Y7 film exhibited a relatively low roughness\nof 1.7 nm, obtained without the use of postprocessing methods. The\nc-AFM quantitative analysis was carried out on the active film with\nand without the electron transport interfacial layer (PFN) of the\ncell structure, which confirmed that the addition of PFN on top of\nPM6:Y7 enhanced conductive pathways with high current and low resistance\nvalues.