While OPV offers great promise as a low-cost renewable energy source, the relatively low efficiency still challenges its commercialization potential. SQ dyes offer significant potential as a light-absorbing layer in OPV because of their high extinction coefficient, broad spectral absorption, and ease of tuning the chemical structure and packing motif. Devices incorporating SQ dyes, however, have shown low PCE. In this preliminary work, we seek to explore the relationship between low power conversion efficiency (PCE) of Squaraine (SQ) related Organic Photovoltaics (OPV) systems and the formation of aggregates with the help of mixed SQs in ternary blends. Four aniline based SQ molecules, - DBSQ(OH)2 (2,4-Bis[4-(N,N-dibutylamino)-2,6-dihydroxyphenyl] Squaraine), DiPSQ(OH)2 (2,4-Bis[4-(N,N-diisopentylamino)-2,6-dihydroxyphenyl] Squaraine), DiBSQ(OH)2 (2,4-Bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] Squaraine), and DHSQ(OH)2 (2,4-Bis[4-(N,N-dihexylamino)-2,6-dihydroxyphenyl] Squaraine), with two different packing motifs were investigated. DBSQ(OH)2 and DHSQ(OH)2 align in a slip stacked packing, DiBSQ(OH)2 aligns in herringbone packing while DiPSQ(OH)2 is expected to align in herringbone packing. In binary SQ-PCBM [Phenyl-C61 butyric acid and methyl ester] devices, PCE of SQs with PCBM in the order of DBSQ(OH)2 [3.34%] > DHSQ(OH)2 [2.42%] > DiBSQ(OH)2 [1.44%] > DiPSQ(OH)2 [1.27%] were achieved. All ternary blends showed disruption in aggregation, which increased the PCE. [DBSQ(OH)2: DHSQ(OH)2: PCBM] showed an increase of 12.57% in efficiency from binary [DBSQ(OH)2: PCBM] blend. [DiBSQ(OH)2: DiPSQ(OH)2: PCBM] showed an increase of 42.30% from the binary DiBSQ(OH)2 and PCBM blend. When SQs with different packing motifs ([DBSQ(OH)2 and DiBSQ(OH)2] and [DHSQ(OH)2 and DiPSQ(OH)2]) were mixed with PCBM, the results showed an increase in efficiency in relation to herringbone packed SQs but were less efficient than the slip-stacked packed SQs. We provide a series of speculations and interpretations to explain such behaviour of SQs on PCE of SQ based devices. We conclude that the mixing of SQs with similar packing motif has a positive impact on the efficiency of the devices. Furthermore, suggestions for follow-up work are implied given that a thorough treatment of the results is beyond the scope of the work for this thesis.
Department, Program, or Center
School of Chemistry and Materials Science (COS)
Christopher J. Collison
Jeremy A. Cody
Gupta, Soumya, "Aggregation as an efficiency driver in bulk heterojunction devices measured through mixed Squaraines in ternary blends" (2020). Thesis. Rochester Institute of Technology. Accessed from
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