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%.

Ultraviolet (UV) organic optoelectronic devices have been attracting extensive research owing to their great potential in a variety of applications such as biological and chemical sensing, excitation lighting source, high-density...

Two novel asymmetrical squaraines based on the indoline unit, ASQ-5-F and ASQ-5-DF, with one and two fluorine substituents, have been developed to investigate the effect of fluorine substituted on small-molecule bulk-heterojunction (BHJ) organic solar cells (OSCs). In comparison with non-fluorine-substituted ASQ-5, both fluorine-substituted ASQ-5-F and ASQ-5-DF possess analogous absorption band gaps but 0.05 and 0.10 eV lowered highest occupied molecular orbital (HOMO) energy levels, respectively. Single-crystal analysis exhibits that ASQ-5-DF shows more desirable intermolecular packing patterns for the hole-carrier collection than ASQ-5 does; hence, higher hole mobility could be acquired. Therefore, solution-processed small-molecule BHJ OSCs fabricated with ASQ-5-F/PC71BM and ASQ-5-DF/PC71BM blends exhibit extremely higher power conversion efficiency (PCE; 5.0% and 6.0%, respectively) than that of ASQ-5/PC71BM (4.5%). The much improved PCE could be attributed to the simultaneously enhanced Voc, Jsc, and FF relative to those of the ASQ-5-based device. To our knowledge, this is the highest PCE (6.0%) among squaraine-based solution-processed BHJ OSCs and the highest PCE in OSCs based on the fluorinated donor segment of small molecules.

A novel asymmetrical squaraine ASQ-5 bearing indoline as an end capper exhibits a low bandgap of 1.43 eV and a broad absorption band in the Vis-NIR region of 550-850 nm in thin films, hence renders solution-processed organic solar cells with an impressive Jsc of up to 11.03 mA cm(-2) and an excellent PCE of 4.29%.

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Semitransparent organic solar cells (ST-OSCs) exhibit highly promising applications to develop integrated photovoltaics and power-generating windows. However, the development of ST-OSCs is significantly lagging behind opaque OSCs, especially for all small-molecule ST-OSCs. Here, four unique squaraines dyes (IDPSQ, SQ-BP, D-BDT-SQ, and AzUSQ) were successfully used as donors in ST-OSCs, whose colors can be tuned from purple to blue, green, and dark green, respectively. While using ultrathin Ag as a transparent electrode, the ST-OSCs fabricated using IDPSQ:PCBM, SQ-BP:PCBM, D-BDT-SQ:PCBM, and AzUSQ:PCBM yield power conversion efficiencies (PCEs) of 2.96, 4.36, 4.91, and 1.71%, respectively, and their colors are purple, cyan, brown, and light brown, respectively. Compared to their opaque OSCs (PCEs of 3.95, 5.45, 5.84, and 1.91%, respectively), the reduction in the PCEs are as low as 25, 20, 16, and 10%, respectively. Furthermore, each of these ST-OSCs exhibit good average visible transmittance (AVT) of 25-30%, favorable CIE color coordinates, and a color rendering index (CRI) of 71-97%. Finally, by changing the thickness of the Ag electrode, an impressive PCE of 4.9% along with an AVT of 25% and a CRI of 97% can be obtained in D-BDT-SQ:PCBM-based ST-OSCs, which is the highest PCE among all small-molecule ST-OSCs.

Electronic supplementary information (ESI) available: electron density distribution and absorption spectra of the active layers.Abstract: A novel asymmetrical squaraine derivative bearing cyano-substituted indoline end-capping group, namely ASQ-5-CN, was designed and synthesized. In comparison with the noncyano-substituted ASQ-5, ASQ-5-CN shown an analogous absorption band-gap in thin solid film state, but a 0.11 eV lowered HOMO energy level, which led to a higher V oc .Density functional theory calculation results revealed that the dipole moment of ASQ-5-CN was 2 times larger than that of ASQ-5. Hence the stronger dipole-dipole interactions of ASQ-5-CN might trigger more intense intermolecular packing in ASQ-5-CN, which should account for the higher hole-mobility of ASQ-5-CN than that of ASQ-5 (4.00 ×10 -5 vs. 1.67 ×10 -5 cm 2 V -1 s -1 ). Accordingly, solution-processed bulk-heterojunction small molecular organic solar cell using ASQ-5-CN as electron donor exhibited much higher PCE (5.24%) than that of the reference compound ASQ-5-based device (4.22%) due to its simultaneously enhanced V oc (0.92 vs. 0.82 V), J sc (11.38 vs. 10.94 mA cm -2 ) and FF (0.50 vs. 0.47).

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