Controlling J-aggregate formation for increased short-circuit current and power conversion efficiency with a squaraine donor

A squaraine dye is tested for novel application in a near-infrared-active organic photovoltaic cell that is subsequently optimized to obtain a power conversion efficiency of 2.4 +/- 0.3%. The optimization utilizes an Alq3 buffer layer and macroscopic structure control through the addition of co-solvents in the spin-casting process. Co-solvent addition increases the amount of aggregates present as measured through linear absorption spectroscopy, and there is a concurrent increase in both efficiency and short-circuit current. An interpretation of the greatly increased current density is presented that describes how increased J-aggregation likely increases hole mobility and, as a result, charge separation of the photogenerated excited state. Copyright (c) 2012 John Wiley & Sons, Ltd.