Pyrene is a quite promising structural unit for HLCT emitters, and deep-blue OLEDs showing quite high brightness over 10 000 cd m⁻² and EQE_max over 10.5% have been achieved.

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 V_oc of up to 1.12 V and a PCE of 2.82%.

A novel asymmetrical squaraine derivative bearing a 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 showed an analogous absorption band-gap in the 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 over double 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 × 10⁻⁵vs. 1.67 × 10⁻⁵ cm² V⁻¹ s⁻¹). Accordingly, solution-processed bulk-heterojunction small molecular organic solar cells using ASQ-5-CN as the electron donor exhibited a 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). Additionally, the PCE of the ASQ-5-CN-based device could be improved to be as high as 6.11% when measured at 80 °C, which is the record PCE among the hitherto reported squaraine-based solution-processed bulk-heterojunction organic solar cells.