Enhanced performance in polymer solar cells by the use of a halogenated indium tin oxide anode

Use of a halogenated, surface-modified indium tin oxide (ITO) anode was found to enhance the photovoltaic performance of a bulk heterojunction (BHJ) polymer solar cell using poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) by as much as 29% but produced no enhancement in a BHJ device using poly(3-hexylthiophene). The position of the positive polaronic state of the polymer was found to be crucial to the enhancement. A power conversion efficiency of 6.27% for a PCDTBT-based BHJ device was achieved by using a chlorinated ITO anode without the needs of using any modifying interlayer or optical spacer at the cathode.