Novel high performance asymmetrical squaraines for small molecule organic solar cells with a high open circuit voltage of 1.12 V

Abstract

An asymmetrically substituted squaraine ASQC bearing a 9-carbazyl substituent exhibits an extremely deep HOMO energy level of -5.46 eV and a relatively low bandgap of 1.65 eV, hence renders solution-processed organic solar cells with an impressive Voc of up to 1.12 V and a PCE of 2.82%.

Asymmetrical Squaraines Bearing Fluorine-Substituted Indoline Moieties for High-Performance Solution-Processed Small-Molecule Organic Solar Cells

“…22 n-Butanol and toluene were distilled from sodium freshly prior to use. All other chemicals were obtained from commercial sources and used as-received without further purification.…”

N,N-Diarylamino end-capping as a new strategy for simultaneously enhancing open-circuit voltage, short-circuit current density and fill factor in small molecule organic solar cells

“…16 The J-V curves of the devices are illustrated in Fig. 16 The J-V curves of the devices are illustrated in Fig.…”

“…16 Although ASQB displays a relatively low bandgap and good solubility owing to the presence of an electron-rich N,N-diisobutylamino group in it, the PCE of the corresponding BHJ-SMOSCs is unsatisfactory (1.54%), with low V oc of 0.75 V, J sc of 5.40 mA cm À2 , and FF of 0.38. 16 Although ASQB displays a relatively low bandgap and good solubility owing to the presence of an electron-rich N,N-diisobutylamino group in it, the PCE of the corresponding BHJ-SMOSCs is unsatisfactory (1.54%), with low V oc of 0.75 V, J sc of 5.40 mA cm À2 , and FF of 0.38.…”

“…16 Although ASQB displays a relatively low bandgap and good solubility owing to the presence of an electron-rich N,N-diisobutylamino group in it, the PCE of the corresponding BHJ-SMOSCs is unsatisfactory (1.54%), with low V oc of 0.75 V, J sc of 5.40 mA cm À2 , and FF of 0.38. 16 Moreover, recent research works have revealed that the replacement of N,Nalkylamino with N,N-diarylamino substituents in photovoltaic materials could not only lead to more intensied intermolecular p-p overlap that benets the broaden of the absorption spectra and the enhancement of charge-transporting properties in lm states, 19,20 hence higher J sc could be expected; but also endow these compounds with dropped HOMO energy levels, hence higher V oc could also be expected. 17,18 Additionally, by replacing the end-capper with a carbazolyl group, the resulting compound ASQC was found to show considerably lowered HOMO energy level, hence ASQC-based SMOSCs displays a very high V oc ; however, ASQC exhibits a higher energy bandgap with that of ASQB.…”

Cyano-substitution on the end-capping group: facile access toward asymmetrical squaraine showing strong dipole–dipole interactions as a high performance small molecular organic solar cells material

“…For example, the record power conversion efficiency (PCE) of solution-processed squaraine-based BHJ-OSC is only 5.50%, note that the squaraine compound used just possesses a symmetrical molecular structure with a D-A-D skeleton. [24][25][26][27] Through delicate modulation on the end-capping group of the D′ segment, such as diisobutylamino, 9-carbazyl, diarylamino, tetrahydroquinoline and indoline, a series of ASQ materials were achieved, and one of them bearing an indoline end-capping subunit (named ASQ-5, molecular structure shown in Fig.1) displayed the highest photovoltaic performance (PCE=4.29%). [22,23] Consequently, recently, we have devoted to the development of novel ASQ materials for BHJ-OSC applications, in which 1,1,2-trimethyl-1H-benzo [e] indole acts as the D subunit, squaric acid core acts as the A subunit, and 2,6-dihydroxyphenyl group acts as the D′ subunit.…”