Self‐Organized Anode Interlayer Enables PEDOT:PSS‐Free Structure for Thick‐Film Organic Solar Cells over 16% Efficiency

Thickness‐insensitivity of organic solar cells (OSCs) is a crucial issue for transformation from the laboratory‐scale devices to large‐area solar panels. Generally, the low carrier mobility of organic semiconductors hindering charge transport process leads to severe recombination losses and further poisons the fill factor (FF) in thick‐film OSCs. Herein, a PEDOT:PSS‐free pseudoplanar heterojunction OSC from sequential deposition method with self‐organized [2‐(9H‐carbazol‐9‐yl)ethyl]phosphonic acid interlayer is fabricated. The notable power conversion efficiency (PCE) enhancement from PEDOT:PSS‐based device of 17.0% to PEDOT:PSS‐free device of 17.8% is obtained in thin‐film devices (≈100 nm), which is correlated to the improved incident photons absorption by the absence of PEDOT:PSS. Besides, the PEDOT:PSS‐free device exhibits excellent thickness tolerance, with FF only degrades from 78.4% to 72.9% when the active layer thickness increases from ≈100 to ≈300 nm. The insights of remained FF are further traced to notably mitigated nongeminate recombination losses of PEDOT:PSS‐free structure. The strengthened charge extraction is also verified by reinforced built‐in potential and desirable and balanced mobilities. Consequently, the PEDOT:PSS‐free device with ≈300 nm active layer yields an inspiring PCE of 16.4%, much higher than that of PEDOT:PSS‐based device of 14.5%.