The development of novel, efficient and cost-effective emitters for solid-state lighting devices (SSLDs) is ubiquitous to meet the increasingly demanding needs of advanced lighting technologies. In this context, the emergence of thermally activated delayed fluorescence (TADF) materials has stunned the photonics community. In particular, inorganic TADF material-based compounds can be ad hoc engineered by chemical modification of the coordinated ligands and the type of metal centre, allowing control of their ultimate photo-/electroluminescence properties, while providing a viable emitter platform for enhancing the efficiency of state-of-the-art organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LECs). By presenting an overview of the state of the art of all metal complex-based TADF compounds, this review aims to provide a comprehensive, authoritative and critical reference for their design, characterization and device application, highlighting the advantages and drawbacks for the chemical, photonic and optoelectronic communities involved in this interdisciplinary research field.

The toxicity risks, instability of essential oil, and complex composition are principal obstacles to using essential plant oil for clinical applications. Solving stability-related problems, providing targeted drug delivery, and decreasing plant essential oil toxicity, encapsulation can be used successfully. Rosemary (Rosmarinus officinalis) is a perennial plant of the Lamiaceae family with various healing properties. However, the rosemary essential oil, as volatile oil, is fast evaporated, which limits its applications. This study’s goal is to boost the prevent evaporation and bioactivity of rosemary essential oil by developing zein-NPs as a promising NDS (nano-drug-delivery system) and assessing the effect of NPs on the rosemary essential oil efficacy. Scanning electron microscopy (SEM) showed NPs sizes between 70–200 nm. With dynamic light scattering analysis (DLS), the average size of zein nanoparticle-containing rosemary essential oil (NPZLA) was obtained at ca. 154.5 nm. The entrapment efficiency (EE) on rosemary essential oil was ca. 71% inside the zein NPs. The in vitro release suggests that the polymeric barrier can control the rosemary essential oil release. Zein-NPs can be potentially used as NC (nanocarrier) for enhancing the evaporation inhibitor of ether oil of rosemary essential oil to enhance its bioavailability and performance further. It can be concluded that rosemary plant can be used as the core inside the nanoparticle by biological production method due to its medicinal properties and other properties. Based on the stated content, it is clear that in the future, by conducting more extensive research, the necessary platform can be provided for the use of this medicinal plant as much as possible in the pharmaceutical industry.

In an effort to diminish the cost of perovskite solar cells (PSCs) with regard to hole transport materials (HTMs), we employed an easily attainable condensation route to synthesize a cheap and efficient HTM. Using a newly engineered small organic molecule, N,N′-(naphthalene-1,5-diyl)bis(1-(2,3-diphenylquinoxalin-6-yl)-1-phenylmethanimine), coded as BEDN, the power conversion efficiency (PCE) reached 17.85%, comparable to that of the state-of-the-art HTM spiro-OMeTAD (19.50%). The BEDN's estimated cost is 1.38 ($ per g), which is considerably cheaper than spiro-OMeTAD, 92 ($ per g). The low cost and high efficiency are promising in commercialization of perovskite solar cells.

In perovskite solar cells (PSCs), hole transporting materials (HTMs) play a critical role in determining the stability and efficiency of the devices. However, the high cost and complex synthesis processes associated with conventional HTMs can hinder their widespread applications. This work presents a low-cost and efficient HTM, namely N,N′-(naphthalene-1,5-diyl)bis(1-(dibenzo[a,c]phenazin-11-yl)-1-phenylmethanimine) (PEDN), based on a naphthalene core with an extended π-conjugation system for improving the performance of PSCs. The PEDN was synthesized via a facile two-step condensation method, eliminating the need for expensive catalysts such as BINAP. The newly developed HTM with an extended π-conjugation length was compared with BEDN and spiro-OMeTAD as the benchmark HTM, in terms of their optical, electrochemical, hole mobility properties, and efficiency in PSCs. The PEDN showed suitable highest occupied molecular orbital levels (HOMOs), good hole mobilities, as well as strong hydrophobicities. The extended π-conjugation system in PEDN contributes to the stability of the solar cells. The PSCs fabricated with PEDN achieved a high efficiency of 18.61%, comparable to the efficiency obtained using the commonly used HTM spiro-OMeTAD (19.68%). Furthermore, the cost-effectiveness of PEDN makes it a suitable alternative to spiro-OMeTAD for PSC applications.