Intrinsic electro-optical and thermodynamic properties of 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP) as a potential candidate for nonlinear optical applications: a DFT investigation
摘要
In this work, the electronic, transport, photophysical, thermodynamic, linear, and nonlinear optical properties of intrinsic 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP) were investigated. The results show that CBP is an insulator with a bandgap of 4.07 eV, exhibiting good holes mobility (1.52 cm2V⁻1 s⁻1) and thermodynamic stability. A nonlinear optical (NLO) analysis reveals a static first-order hyperpolarizability (1.97 × 10⁻3⁰ esu) exceeding that of urea (0.32 × 10⁻3⁰ esu), and a second-order hyperpolarizability (98.94 × 10⁻3⁶ esu), 7 times greater than that of para-nitroaniline (12.71 × 10⁻3⁶ esu). In the dynamic mode at 1064 nm, CBP demonstrates an enhanced NLO response compared to static mode. Its second-order susceptibility (2.27 pm.V⁻1) is 2 times greater than that of quartz (1 pm.V⁻1), and its third-order susceptibility (15.65 × 10⁻22 m2V⁻2) is higher than that of silica (2 × 10⁻22 m2V⁻2). Photophysically, CBP exhibits a near-UV absorption maximum at 253 nm with an oscillator strength of 0.77 and a light collection efficiency of 0.83. The emission spectrum shows a near-UV maximum at 280 nm with a FWHM of 30.25 nm, a radiative lifetime of 1.34 ns and CIE coordinates (0.175, 0.005). These results suggest that CBP, widely known as a good holes transport material in optoelectronic devices, does also have a potential as a near-UV absorber for transparent organic solar cells (TSC), as well as an emitter for first-generation organic light-emitting diodes (OLED) used in lithography and sterilization. Furthermore, CBP can also be used in electro-optical devices such as optical modulators, switches and frequency conversion.