Polymer bulk heterojunction photovoltaics employing a squaraine donor additive

We investigate the effects of adding a functionalized squaraine donor 2,4-bis[4-(N,N-diphenylamino)-2,6-dihydroxyphenyl] squaraine (DPSQ) into a conventional poly(3-hexylthiophene)(P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) polymer bulk heterojunction photovoltaic cell. The near infrared absorption of the blend was enhanced by the DPSQ additive, resulting in an increased power conversion efficiency of the P3HT:PCBM devices by >20%. A maximum power conversion efficiency of 3.4 ± 0.3% and an external quantum efficiency as high as 55% was achieved for a P3HT:PCBM blend that included 5 wt.% DPSQ.

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► A polymer/small molecule blend extends OPV sensitivity into the near infrared.
► Squarines and P3HT both show photo activity in this ternary OPV.
► Mixtures up to 10% squaraine significantly increase quantum efficiency.