Built-in voltage enhanced by: In situ electrochemical polymerized undoped conjugated hole-transporting modifiers in organic solar cells

Herein, a new electropolymerized (EP) film named poly-triphenylcarbazole fluoranthene (p-TPCF) has been in situ synthesized by an electrochemical cyclic voltammetry method and applied to tune the work-function (WF) of the PEDOT:PSS hole-transporting layer (HTL) in organic solar cells (OSCs). Multiple techniques, including Kelvin probe force microscopy (KPFM), light intensity dependent solar cell characterization, Mott-Schottky analysis, and transient photovoltage (TPV) and transient photocurrent (TPC) measurements, have been explored to provide insights into the mechanism. Benefiting from the deeper work-function (WF), larger built-in voltage (V_bi), decreased recombination, and longer carrier lifetime, the devices with EP films exhibited superior device performance with simultaneously enhanced V_oc, J_sc and FF.