Dr. Tunde Blessed Shonde

The growing demand for efficient, low-cost, and scalable direct X-ray detectors has prompted the exploration of materials beyond conventional inorganic semiconductors, e.g., Si, α-Se, and Cd(Zn)Te. While organic semiconductors offer attractive features, including mechanical flexibility and low-temperature solution processability, they often fall short in sensitivity, energy resolution, and detection limits compared to their inorganic counterparts. Here, the first demonstration of direct X-ray detectors is reported based on a new class of materials, organic metal halide complexes (OMHCs), which are composed of metal halide species covalently bonded to organic semiconducting units. Specifically, 4-(4-(diphenylamino) phenyl)-1-(propyl)-pyridinium zinc bromide ((TPA-Py)
ZnBr
) is employed in its glassy form to fabricate high-performance direct X-ray detectors. By applying a facile melt-processing approach, wet-chemistry-synthesized (TPA-Py)
ZnBr
single crystals can be easily transformed into air-stable glassy samples with tunable dimensions for device integration. The resulting glassy OMHC-based X-ray detectors exhibit outstanding performance, including a high dark resistivity (5.37 × 10
Ω cm), an excellent detection sensitivity (2,020 µC Gy
cm
) at an electric field of 10 V mm
, and an ultralow detection limit of 12.44 nGy
s
. These results establish semiconducting OMHC glasses as a highly promising new class of materials for direct X-ray detectors.

Zero-dimensional (0D) organic metal halide hybrids (OMHHs) are emerging materials with significant potential for optoelectronic applications, including direct X-ray detectors. While 0D OMHH single crystals exhibit excellent X-ray detection properties, their scalability remains a significant challenge due to the time-intensive growth process and difficulty in producing large single crystals exceeding a few centimeters. This limitation hinders their practicality for large-area detector applications. Here, we report for the first time the development of amorphous 0D OMHH films via solution processing for efficient direct X-ray detection. By reacting a non-crystalline organic halide, triphenyl(9-phenyl-9H-carbazol-3-yl)phosphonium bromide (TPPCarzBr), with zinc bromide (ZnBr2), we have successfully produced amorphous 0D (TPPCarz)2ZnBr4 films with controlled thickness via facile solution processing. The organic cations (TPPCarz⁺) feature a lower bandgap than the ZnBr42− anions, enabling efficient molecular sensitization, where ZnBr42− anions serve as X-ray absorbers and TPPCarz⁺ cations as charge transporters. Direct X-ray detectors based on 0D (TPPCarz)2ZnBr4 films demonstrate outstanding performance, achieving a stable X-ray detection sensitivity of 2,165 µC Gyair⁻1cm⁻2 at 20 V mm⁻¹ and a detection limit of 6.01 nGyair s⁻¹. The amorphous nature of these films enhances their processability, allowing for fabrication in various sizes and shapes, and making them highly adaptable for scalable detector applications.

Metal halide perovskites and perovskite-related organic metal halide hybrids (OMHHs) have recently emerged as a new class of luminescent materials for light emitting diodes (LEDs), owing to their unique and remarkable properties, including near-unity photoluminescence quantum efficiencies, highly tunable emission colors, and low temperature solution processing. While substantial progress has been made in developing monochromatic LEDs with electroluminescence across blue, green, red, and near-infrared regions, achieving highly efficient and stable white electroluminescence from a single LED remains a challenging and under-explored area. Here, a facile approach to generating white electroluminescence is reported by combining narrow sky-blue emission from metal halide perovskites and broadband orange/red emission from zero-dimensional (0D) OMHHs. For the proof of concept, utilizing TPPcarz+ passivated two-dimensional (2D) CsPbBr3 nanoplatelets (NPLs) as sky blue emitter and 0D TPPcarzSbBr4 as orange/red emitter (TPPcarz+ = triphenyl (9-phenyl-9H-carbazol-3-yl) phosphonium), white LEDs (WLEDs) with a solution processed bilayer structure have been fabricated to exhibit a peak external quantum efficiency (EQE) of 4.8% and luminance of 1507 cd m-2 at the Commission Internationale de L'Eclairage (CIE) coordinate of (0.32, 0.35). This work opens a new pathway for creating highly efficient and stable WLEDs using metal halide perovskites and related materials.

0D organic metal halide hybrids (OMHHs) have recently emerged as a new generation of scintillation materials, due to their high luminescence quantum efficiency, sensitivity, stability, and cost-effectiveness. While numerous 0D OMHH scintillators have been developed to date, most of them are based on solution grown single crystals that require time-consuming synthesis and are limited in size. Here, high-performance X-ray scintillators based on facile solution processed 0D OMHH amorphous films are reported for the first time. By reacting triphenyl(9-phenyl-9H-carbazol-3-yl) phosphonium bromide (TPPcarzBr) with manganese bromide (MnBr2), 0D (TPPcarz) MnBr amorphous films can be prepared via solution processing with mild thermal annealing, which exhibits green photoluminescence with an emission maximum approximate to 517 nm and a photoluminescence quantum efficiency of approximate to 87%. The X-ray scintillation of 0D (TPPcarz) MnBr amorphous films is characterized to exhibit a light yield of 44600 photon MeV-1 and an outstanding linearity with a low limit of detection of 32.42 nGyairs-1 over a wide range of X-ray dose rates. The versatile processability of 0D (TPPcarz) MnBr is illustrated with remarkable recyclability, high cost-effectiveness, and scalability for large-scale production. By taking advantage of the amorphous nature of newly designed OMHHs, the approach opens up new opportunities for developing high-performance, solution-processable scintillators.

The expanding applications of X-ray scintillation across various areas, from healthcare to security detection call for the development of new-generation scintillators that offer enhanced sensitivity, efficiency, and versatility. Here, we report for the first time the use of organic metal halide complexes with aggregation-induced emission (AIE) for X-ray scintillation, which can be facilely synthesized and processed in the solution phase. By reacting an AIE organic molecule, 4-(4-(diphenylamino) phenyl)-1-(propyl)-pyridinium (TPA-PD) with zinc chloride (ZnCl2) in solution at room temperature, an organic metal halide complex, (TPA-PD)(2)ZnCl2, is produced with a high synthetic yield of 87%. Optical and radioluminescence characterizations find that (TPA-PD)(2)ZnCl2 exhibits bluish-green photoluminescence and radioluminescence peaked at around 450 nm, with a photoluminescence quantum efficiency (PLQE) of 65%, and an absolute light yield of 13423 Photon per MeV. Moreover, short photoluminescence and radioluminescence decay lifetimes are recorded at 1.81 ns and 5.24 ns, respectively. For X-ray scintillation, an excellent response dose-response linearity and a low limit of detection of 80.23 nGy(air) S-1 are obtained for (TPA-PD)(2)ZnCl2. By taking advantage of the high X-ray absorption of metal halides and fast radioluminescence of AIE molecules, our design of covalently bonded organic metal halide complexes opens up new opportunities for the development of high-performance solution-processable scintillators.

Metal halide perovskite nanocrystals (NCs) have emerged as highly promising light emitting materials for various applications, ranging from perovskite light-emitting diodes (PeLEDs) to lasers and radiation detectors. While remarkable progress has been achieved in highly efficient and stable green, red, and infrared perovskite NCs, obtaining efficient and stable blue-emitting perovskite NCs remains a great challenge. Here, a facile synthetic approach for the preparation of blue emitting CsPbBr3 nanoplatelets (NPLs) with treatment by an organic sulfate is reported, 2,2-(ethylenedioxy) bis(ethylammonium) sulfate (EDBESO4), which exhibit remarkably enhanced photoluminescence quantum efficiency (PLQE) and stability as compared to pristine CsPbBr3 NPLs coated with oleylamines. The PLQE is improved from approximate to 28% for pristine CsPbBr3 NPLs to 85% for EDBESO4 treated CsPbBr3 NPLs. Detailed structural characterizations reveal that EDBESO4 treatment leads to surface passivation of CsPbBr3 NPLs by both EDBE2+ and SO42- ions, which helps to prevent the coalescence of NPLs and suppress the degradation of NPLs. A simple proof-of-concept device with emission peaked at 462 nm exhibits an external quantum efficiency of 1.77% with a luminance of 691 cd m(-2) and a half-lifetime of 20 min, which represents one of the brightest pure blue PeLEDs based on NPLs reported to date.

Scintillators, one of the essential components in medical imaging and security checking devices, rely heavily on rare-earth-containing inorganic materials. Here, a new type of organic-inorganic hybrid scintillators containing earth abundant elements that can be prepared via low-temperature processes is reported. With room temperature co-crystallization of an aggregation-induced emission (AIE) organic halide, 4-(4-(diphenylamino) phenyl)-1-(propyl)-pyrindin-1ium bromide (TPA-PBr), and a metal halide, zinc bromide (ZnBr2), a zero-dimensional (0D) organic metal halide hybrid (TPA-P)(2)ZnBr4 with a yellowish-green emission peaked at 550 nm has been developed. In this hybrid material, dramatically enhanced X-ray scintillation of TPA-P+ is achieved via the sensitization by ZnBr42-. The absolute light yield (14,700 +/- 800 Photons/MeV) of (TPA-P)(2)ZnBr4 is found to be higher than that of anthracene (approximate to 13,500 Photons/MeV), a well-known organic scintillator, while its X-ray absorption is comparable to those of inorganic scintillators. With TPA-P+ as an emitting center, short photoluminescence and radioluminescence decay lifetimes of 3.56 and 9.96 ns have been achieved. Taking the advantages of high X-ray absorption of metal halides and efficient radioluminescence with short decay lifetimes of organic cations, the material design paves a new pathway to address the issues of low X-ray absorption of organic scintillators and long decay lifetimes of inorganic scintillators simultaneously.

Zero-dimensional (0D) organic metal halide hybrids (OMHHs) have recently emerged as a new class of light emitting materials with exceptional color tunability. While near-unity photoluminescence quantum efficiencies (PLQEs) are routinely obtained for a large number of 0D OMHHs, it remains challenging to apply them as emitter for electrically driven light emitting diodes (LEDs), largely due to the low conductivity of wide bandgap organic cations. Here, the development of a new OMHH, triphenyl(9-phenyl-9H-carbazol-3-yl) phosphonium antimony bromide (TPPcarzSbBr(4)), as emitter for efficient LEDs, which consists of semiconducting organic cations (TPPcarz(+)) and light emitting antimony bromide anions (Sb2Br82-), is reported. By replacing one of the phenyl groups in a well-known tetraphenylphosphonium cation (TPP+) with an electroactive phenylcarbazole group, a semiconducting TPPcarz(+) cation is developed for the preparation of red emitting 0D TPPcarzSbBr(4) single crystals with a high PLQE of 93.8%. With solution processed TPPcarzSbBr(4) thin films (PLQE of 86.1%) as light emitting layer, red LEDs are fabricated to exhibit an external quantum efficiency (EQE) of 5.12%, a peak luminance of 5957 cd m(-2), and a current efficiency of 14.2 cd A(-1), which are the best values reported to date for electroluminescence devices based on 0D OMHHs.

FLASH radiation therapy is a novel technique combining ultra-high dose rates (UHDR) with very short treatment times to strongly decrease normal tissue toxicity while preserving the anti-tumoral effect. However, the radiobiological mechanisms and exact conditions for obtaining the FLASH-effect are still under investigation. There are strong indications that parameters defining the beam structure, such as dose per pulse, instantaneous dose rate and pulse repetition frequency (PRF) are of importance. UHDR irradiations therefore come with dosimetric challenges, including both dose assessment and temporal ones. In this work, a first characterization of 6 real-time point scintillating dosimeters with 5 phosphors (AlO:C,Mg; YO:Eu; AlO:C; (C38H34P)MnBr and (C38H34P)MnCl, was performed in an UHDR pulsed electron beam. The dose rate independence of the calibration was tested by calibrating the detector at conventional and UHDR. Dose rate dependence was observed, however, further investigation, including intermediate dose rates, is needed. Linearity of the response with dose was tested by varying the number of pulses and a linearity with R 0.9989 was observed up to at least 200 Gy. Dose per pulse linearity was investigated by variation of the pulse length and SSD. All point scintillators showed saturation effects up to some extent and the instantaneous dose rate dependence was confirmed. A PRF dependence was observed for the AlO:C,Mg and AlO:C- based point scintillators. This was expected as the luminescence decay time of these materials exceeds the inter-pulse time.

X-ray scintillators based on organic chromophores have the potential to deliver low-cost radiation detection products with fast response signals. However, their relatively low performance compared with that of widely used inorganic scintillators in terms of X-ray attenuation and light output has limited their applications. Here we report a dramatically improved scintillation performance for a BODIPY dye, difluoro(4-(1,1-dimethylethyl)-2-{1-[4-1,1-dimethylethyl)-3,5-dimethyl-2H-pyrrol-2-ylidene-N] ethyl-3,5-dimethyl-1H-pyrrol-2-ylidene-N]ethyl}-3,5-dimethyl-1H-pyrrolato-N) boron (PM 570), via sensitization by a 0D organic metal halide, tetraphenylphosphonium manganese bromide ((C24H20P)(2)MnBr4). By blending PM 570 and (C24H20P)(2)MnBr4 in an appropriate ratio together in a polydimethylsiloxane matrix, we prepare plastic scintillators to exhibit a more than 15-fold increment of radioluminescence from PM 570. Such an enhancement is attributed to the excellent X-ray scintillation property of (C24H20P)(2)MnBr4 and the efficient energy transfer from (C24H20P)(2)MnBr4 to PM 570. These multicomponent plastic scintillators also exhibit an excellent linear response to the X-ray dose rate and a low detection limit of 22.5 nGy s(-1).