High efficiency organic photovoltaic cells based on a vapor deposited squaraine donor

2,4-bis[4-( N , N -diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SQ) is used as a donor material in vapor deposited organic heterojunction photovoltaic cells. Devices with the structure indium tin oxide/SQ ( x ) ∕ C 60 ( 400 Å ) /bathocuproine ( 100 Å ) ∕ Al ( 1000 Å ) , where x = 65 , 110, 150, and 200 Å were compared. Devices with x = 65 Å exhibited a power conversion efficiency of 3.1% under 1 sun , AM1.5G simulated solar irradiation, giving an open circuit voltage of 0.76 ± 0.01 V , a short circuit current of 7.01 ± 0.05 mA ∕ cm 2 , and a fill factor of 0.56 ± 0.05 . Thicker SQ films lead to lower short circuit currents and fill factors, giving conversion efficiencies in the range of 2.6% to 3.2%. The demonstration of sublimable SQ as a donor material opens up a family of compounds for use in small molecule based heterojunction photovoltaics.