Impact of fluorination on optoelectronic properties of thiophene-benzothiadiazole-based hole-transport polymers for perovskite solar cells

Novel polymers composed of thiophene units combined with non-fluorinated and fluorinated 2,1,3-benzothiadiazole units were synthesized and investigated as hole transport materials in perovskite solar cells. The impact of backbone fluorination on the optical and electronic properties of the resulting materials as well as the nanoscale morphology of their films deposited on the perovskite absorber layer was elucidated. The fluorinated polymer provided a superior power conversion efficiency of 18.6% coupled with high open-circuit voltage (V_OC = 1.047 V) and short-circuit current (J_SC = 23.4 mA cm⁻²).