Rational design of high-performance soluble intrinsic black polyimide with full absorption of visible light

With the rapid development of photoelectric devices, the demand for black polyimide (BPI) with excellent masking ability is growing, but existing BPI doped with black substrates has serious insulation and mechanical performance deficiencies. To solve the problem, the intrinsic BPI with excellent comprehensive performance is highly desirable. In this work, tetraphenylcyclopentadienone (TPCP) was chosen as a chromophore, a novel diamine (TPCPtPPDA) containing TPCP grafted with biphenyl groups was synthesized, and TPCPtPPDA was then polymerized with 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to obtain a black polyimide (TPCPtPPPI). The TPCPtPPPI showed full absorption of visible light with cutoff wavelength (λcut) high to 713 nm and Commission International Eclairage (CIE) lab color parameter L* of 0.82. By calculating the frontier molecular orbitals and the nature of electron transitions, the excellent light absorption property was attributed to the electron transition from HOMO to LUMO occurring in the diamine moieties, with the charge transfer mainly from the terphenyl moieties in 2 and 5 positions to the central cyclopentadienone core. Meanwhile, TPCPtPPPI also had excellent thermal, electrical and mechanical performances and solubility by introduction of rigid non-planar propeller-shaped structure. This work provides a promising strategy for constructing high-performance soluble intrinsic BPI and related polymers with full absorption of visible light.