A direct wide bandgap of 6.2 eV, high temperature robustness, and radiation hardness make aluminum nitride (AlN) a preferable semiconductor for deep ultraviolet (UV) photodetection. However, the performance and reliability of AlN-based devices is adversely affected by a large density of surface states present in AlN. In this work, we have investigated the potential of a monolayer of organic molecules in passivating the surface states of AlN, which improved the performance of AlN-based metal− semiconductor−metal (MSM) deep UV photodetector. The organic molecules of the meso-5,10,15-triphenyl-20-(p-hydroxyphenyl)porphyrin Zn(II) complex (ZnTPP(OH)) were successfully adsorbed on an AlN surface, forming a self-assembled monolayer (SAM). The molecular layer was characterized by contact angle measurement, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The surface modification of AlN effectively reduced the dark current of the photodetector by 10 times without degrading the magnitude of photocurrent, especially at low voltages. The photo to dark current ratio (PDCR) was enhanced from 930 to 7835 at −2 V, and the responsivity doubled from 0.3 to 0.6 mA/W at 5 V. Moreover, the rise and fall times of the detector were found to decrease after the surface modification process. Our results suggest that SAM of porphyrin molecules effectively passivated the surface states in AlN, which resulted in improved photodetector performance.

This perspective presents a concise overview of the developments in telluraporphyrinoid chemistry since its inception.

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Regioselective stepwise bromination of meso-tetraaryl [14]­triphyrins­(2.1.1) was explored to investigate the effect of bromine substitution at the β-pyrrole carbons of triphyrin(2.1.1) on the structural, spectral, photophysical, and redox properties. A series of β-monobromo to β-hexabromo triphyrins(2.1.1) 2–7 were synthesized by treating triphyrin(2.1.1) 1 with appropriate equivalents of N-bromosuccinimide at ambient temperature in decent yields. The regiochemistry of bromines in β-brominated triphyrins(2.1.1) 3–5 and 7 was confirmed by X-ray crystallography, and the analysis revealed the effect of bromination of triphyrin(2.1.1) on the structural framework was significant in the case of hexabromotriphyrin(2.1.1) 7 compared to other macrocycles. Absorption spectroscopy showed that stepwise substitution of bromines at β-pyrrole carbons of triphyrin(2.1.1) resulting in bathochromic shifts of absorption bands relative to triphyrin(2.1.1) 1 and hexabromotriphyrin(2.1.1) 7 exhibited absorption bands at longer wavelengths. The redox studies revealed that compounds 2–7 were easier to reduce than triphyrin(2.1.1) 1, and the first reduction potential wave shifted anodically with an increase in the number of bromine substituents at β-pyrrole carbons of triphyrin(2.1.1) 1 from one to six. These structural, spectral, and electrochemical properties were also predicted by density functional theory calculations, and the analysis was consistent with the experimental observations.