Recent Progress and Emerging Applications of Rare Earth Doped Phosphor Materials for Dye‐Sensitized and Perovskite Solar Cells: A Review

Computational, optical and feasibility studies of organic luminescence TMB-PPT blend for photovoltaic application

For enhanced applications of solar cells, organic luminescence materials like long persistent luminescence (LPL) present one of the promising avenues for light enhancement. Currently, most existing luminescent materials are based on an inorganic system that requires rare elements such as europium and dysprosium, with a very high processing temperature. Adopting organic luminescence materials that are free from rare elements is necessary, considering the low-temperature fabrication and low material cost. In this work, we investigate the optical properties of an organic luminescence blend consisting of 2,8-bis(diphenylphosphoryl)dibenzo [b,d]thiophene (PPT) and N,N,N',N'-tetramethylbenzidine (TMB) through computational studies and experimental validations. Optical characteristics of the luminescence materials like optical absorption, photoluminescence, and time-resolved photoluminescence spectroscopy are characterized. To validate the functionality of the organic luminescence blend, the material is incorporated into the perovskite solar cell structure. Unfortunately, the blend is unable to emit sufficient illumination over extended periods due to its low intersystem crossing efficiency and weak spin-orbit coupling. Although the power conversion efficiency of the Luminescence/FTO/TiO2/Perovskite/Carbon structure is observed to be small under dark conditions, the application of organic luminescence materials can be further enhanced and explored.

Tb- and Eu-doped yttrium oxyselenides as novel absorber layers for superstrate thin-film photovoltaics: improved spectral optical absorption and green-red phosphor activation

To generate and deliver alternative sustainable energy in the face of the current energy crisis, new materials that can capture solar energy and transform it into other useful energies are required. Rare-earth (RE) oxychalcogenides are now being used more frequently as up/down-conversion materials in established photovoltaic (PV) devices to boost their PV performance. Here, through an efficient microwave assisted synthesis procedure, novel nanoplate/sheet shaped nanomaterials of yttrium oxyselenide (YOSe) and its analogues doped with Tb and Eu (YOSe:Tb and YOSe:Eu) were successfully synthesized. Analyses of the structure, stability, morphology, light absorption, and electrochemistry were performed. This work showed that the parent YOSe exhibited green (543 nm) and red (615 nm) emission luminescence when doped with Tb and Eu with a luminescence quantum yield (LQY) of 0.56 and 0.53 for YOSe:Tb and YOSe:Eu nanomaterials, respectively. The surface and material conductivity of YOSe improved with the addition of the dopant elements, with the best outcome shown in YOSe:Eu, according to electrokinetic research evidenced by the enhanced current peaks, reduced charge-transfer resistance (Rct) and low impedance magnitude (Zmag) through electrochemical experiments. These improvements were induced by the distinctive properties of the dopant elements. PCEs of 0.25%, 0.67%, and 1.20% were obtained for YOSe, YOSe:Tb, and YOSe:Eu-based PV devices, respectively, using the nanomaterials as novel absorber layers in a superstrate device design. Our results can initiate further exploitation of the doped host structure for effective down-conversion NIR luminescence for applications in PV devices and to boost the PV performance of existing solar cells.

Quantum Modification of Indacenodithieno[3,2-b]thiophene-Based Non-fullerene Acceptor Molecules for Organic Solar Cells of High Efficiency

In order to enhance the efficacy of organic solar cells, six new three-dimensional small donor molecules (IT-SM1 to IT-SM6) have been computationally designed by modifying the peripheral acceptors of the reference molecule (IT-SMR). The frontier molecular orbitals revealed that IT-SM2 to IT-SM5 had a smaller band gap (E_gap) than IT-SMR. They also had smaller excitation energies (E_x) and exhibited a bathochromic shift in their absorption maxima (λ_max) when compared to IT-SMR. In both the gas and chloroform phases, IT-SM2 had the largest dipole moment. IT-SM2 also had the best electron mobility, while IT-SM6 had the best hole mobility owing to their smallest reorganization energy for electron (0.1127 eV) and hole (0.0907 eV) mobility, respectively. The analyzed donor molecules' open-circuit voltage (V_OC) indicated that all of these proposed molecules had greater V_OC and fill factor (FF) values than the IT-SMR molecule. In accordance with the evidence of this work, the altered molecules can seem to be quite proficient for usage by experimentalists and have prospective use in future in the manufacture of organic solar cells with improved photovoltaic properties.

Quantum modeling of dimethoxyl-indaceno dithiophene based acceptors for the development of semiconducting acceptors with outstanding photovoltaic potential

In the current DFT study, seven dimethoxyl-indaceno dithiophene based semiconducting acceptor molecules (ID1-ID7) are designed computationally by modifying the parent molecule (IDR). Here, based on a DFT exploration at a carefully selected level of theory, we have compiled a list of the optoelectronic properties of ID1-ID7 and IDR. In light of these results, all newly designed molecules, except ID5 have shown a bathochromic shift in their highest absorbance (λ _max). ID1-ID4, ID6 and ID7 molecules have smaller band gap (E _gap) and excitation energy (E _x). IP of ID5 is the smallest and EA of ID1 is the largest among all others. Compared to the parent molecule, ID1-ID3 have increased electron mobility, with ID1 being the most improved in hole mobility. ID4 had the best light harvesting efficiency in this investigation, due to its strongest oscillator. The acceptor molecules' open-circuit voltages (V _OC) were computed after being linked to the PTB7-Th donor molecule. Fill factor (FF) and normalized V _OC of ID1-ID7 were calculated and compared to the parent molecule. Based on the outcomes of this study, the modified acceptors may be further scrutinised for empirical usage in the production of organic solar cells with enhanced photovoltaic capabilities.

Quantum chemical modification of indaceno dithiophene-based small acceptor molecules with enhanced photovoltaic aspects for highly efficient organic solar cells

In this computational work, with the aim of boosting the ultimate efficiency of organic photovoltaic cells, seven small acceptors (IDST1-IDST7) were proposed by altering the terminal-acceptors of reference molecule IDSTR. The optoelectronic characteristics of the IDSTR and IDST1-IDST7 molecules were investigated using the MPW1PW91/6-31G(d,p) level of theory, and solvent-state computations were examined using time-dependent density functional theory (TD-DFT) simulation. Nearly all the investigated photovoltaic aspects of the newly proposed molecules were found to be better than those of the IDSTR molecule e.g. in comparison to IDSTR, IDST1-IDST7 exhibit a narrower bandgap (E _gap), lower first excitation energy (E _x), and a significant red-shift in the absorbance maxima (λ _max). According to the findings, IDST3 has the lowest E _x (1.61 eV), the greatest λ _max (770 nm), and the shortest E _gap (2.09 eV). IDST1-IDST7 molecules have higher electron mobility because their RE of electrons is less than that of IDSTR. Hole mobility of IDST2-IDST7 is higher than that of the reference owing to their lower RE for hole mobility than IDSTR. By coupling with the PTB7-Th donor, the open circuit voltage (V _OC) of the investigated acceptor molecules (IDSTR and IDST1-IDST7) was calculated and investigation revealed that IDST4-IDST6 molecules showed higher V _OC and fill factor (FF) values than IDSTR molecules. Accordingly, the modified molecules can be seriously evaluated for actual use in the fabrication of OSCs with enhanced photovoltaic and optoelectronic characteristics in light of the findings of this study.

Engineering of W-shaped benzodithiophenedione-based small molecular acceptors with improved optoelectronic properties for high efficiency organic solar cells

In the current study, with the objective to improve the overall performance of organic solar cells, seven new W-shaped small molecular acceptors – were developed theoretically by the end-group alteration of the reference (WR) molecule. The MPW1PW91 functional with the basis set 6-31G(d,p) was used to explore the optoelectronic properties of the WR and W1–W7 molecules and the time-dependent self-consistent filed (TD-SCF) simulation was used to investigate the solvent-state calculations. The several explored photovoltaic attributes were the absorption spectra, excitation energies, bandgap between the FMOs, oscillator strength, full width at half maximum, light-harvesting efficiency, transition density matrices, open-circuit voltage, fill factor, density of states, binding energy, interaction coefficient, etc. Overall, the results revealed a bathochromic shift in the absorption maxima (λ_max), a reduced HOMO–LUMO gap (E_gap), and smaller excitation energy (E_x) of the altered molecules as compared to the WR molecule. Some of the optoelectronic aspects of a well-known fused ring based acceptor named Y6 are also compared with the studied W-shaped molecules. Additionally, the W1 molecule presented the smallest E_gap, along with highest λ_max and the lowest E_x, amongst all, in both the evaluated media (gas and solvent). The open circuit voltage (V_OC) of all the considered small molecular acceptors was calculated by pairing them with the PTB7-Th donor. Here, W6 and W7 displayed the best results for the V_OC (1.48 eV and 1.51 eV), normalized V_OC (57.25 and 58.41) and FF (0.9131 and 0.9144). Consequently, in light of the results of this research, the altered molecules could be considered for practical implementation in the manufacturing of OSCs with improved photovoltaic capabilities.

The developed molecules have a reduced band gap and lower excitation energy. Their V_OC was calculated by making complexes of them with the PTB7-Th donor.

Novel red color emitting Ca0.995 Mg2 (SO4 )3 :0.5Eu2+ phosphor under UV, blue and green excitation for plant growth LEDs

In the recent few years, Eu²⁺ and Mn⁴⁺ activated phosphors are widely used as potential color converters for indoor plant cultivation lighting application due to their marvellous luminescence characteristics as well as low cost. In this investigation, we are synthesized novel red color emitting Ca_(2-x) Mg₂ (SO₄ )₃ : xmol% Eu²⁺ (x = 0-1.0 mol%) phosphors via solid-state reaction method in reducing atmosphere. The PL excitation spectra of synthesized phosphors exhibited a broad excitation band with three excitation bands peaking at 349 nm, 494 nm and 554 nm. Under these excitations, emission spectra exhibits broad band in the red color region around 634 nm. The PL emission intensity were measured for different concentration of Eu²⁺ . The maximum Eu²⁺ doping concentration in Ca₂ Mg₂ (SO₄ )₃ host was observed for 0.5 mol%. According to Dexter theory, it was determined that dipole-dipole interaction is responsible for concentration quenching. The luminous red color emission of the sample was confirmed by CIE color coordinate. The results of PL excitation and emission spectrum of prepared phosphors are well-matched with excitation and emission wavelengths of phytochrome P_R . Therefore, as per the entire investigation and obtained results it was concluded that the synthesized Ca_0.995 Mg₂ (SO₄ )₃ :0.5mol%Eu²⁺ phosphor has huge potential for plant cultivation application.

Design of a nitridoalumosilicate red phosphor synthesized under mild conditions

A nitridoalumosilicate red phosphor Ca4SiAl3N7:Eu2+ was successfully synthesized at normal pressure and a low temperature (1350 °C).

A review: X-ray excited luminescence of gadolinium based optoelectronic phosphors

X-ray excited fluorescence tomography is an emerging field in the application of bio-imaging and computer tomography. Some rare-earth doped inorganic phosphors like gadolinium oxide (Gd₂ O₃ ), yttrium oxide (Y₂ O₃ ), zinc tungstate (ZnWO₄ ), cesium fluoride (CsF), barium fluorochloride (BaFCl), lanthanum oxybromide (LaOBr) are shown outstanding applications for X-ray excited phosphors. Gadolinium (Gd)-based inorganic phosphors show extraordinary applications in the field of X-ray chromatography and computer chromatography. In this review article, we discussed the general information about X-ray excited luminescence (XEL) phosphor. Further, we discussed importance, synthesis, structural and photoluminescence (PL) properties of rare-earth (Europium (Eu)) doped Gd₂ O₃ . To elaborate the scope of the review, we have discussed synthesis, structural and optical properties of lithium (Li) doped Gd₂ O₃ :Eu. At the end of the review, synthesis, structural and optical properties of Eu doped lutetium oxide (Lu₂ O₃ ) have been discussed and the results compared with Eu doped Gd₂ O₃ . The comparison provided the understanding of structural and optical peak position of host and the dopant (Eu).

High-Performance Perovskite Solar Cells Based on NaCsWO3@ NaYF4@NaYF4:Yb,Er Upconversion Nanoparticles

Extending photoelectric response to the near-infrared (NIR) region using upconversion luminescent (UCL) materials is one promising approach to obtain high-efficiency perovskite solar cells (PSCs). However, challenges remain due to the shortage of highly efficient UCL materials and device structure. NaCsWO₃ nanocrystals exhibit near-infrared absorption arising from the local surface plasmon resonance (LSPR) effect, which can be used to boost the UCL of rare-earth-doped upconversion nanoparticles (UCNPs). In this study, using NaCsWO₃ as the LSPR center, NaCsWO₃@NaYF₄@NaYF₄:Yb,Er nanoparticles were synthesized and the UCL intensity could be enhanced by more than 124 times when the amount of NaCsWO₃ was 2.8 mmol %. Then, such efficient UCNPs were not only doped into the hole transport layer but also used to modify the perovskite film in PSCs, resulting in the highest power conversion efficiency (PCE) reaching 18.89% (that of the control device was 16.01% and the PCE improvement was 17.99%). Possible factors for the improvement of PSCs were studied and analyzed. It is found that UCNPs can broaden the response range of PSCs to the NIR region due to the LSPR-enhanced UCL and increase the visible light reabsorption of PSCs due to the scattering and reflection effect, which generate more photocurrent in PSCs. In addition, UCNPs modify the perovskite film by effectively filling the holes and gaps at the grain boundary and eliminating the perovskite surface defects, which lead to less carrier recombination and then effectively improve the performance of PSC devices.

Photon management to reduce energy loss in perovskite solar cells

Despite the rapid development of perovskite solar cells (PSCs) over the past few years, the conversion of solar energy into electricity is not efficient enough or cost-competitive yet. The principal energy loss in the conversion of solar energy to electricity fundamentally originates from the non-absorption of low-energy photons ascribed to Shockley-Queisser limits and thermalization losses of high-energy photons. Enhancing the light-harvesting efficiency of the perovskite photoactive layer by developing efficient photo management strategies with functional materials and arrays remains a long-standing challenge. Here, we briefly review the historical research trials and future research trends to overcome the fundamental loss mechanisms in PSCs, including upconversion, downconversion, scattering, tandem/graded structures, texturing, anti-reflection, and luminescent solar concentrators. We will deeply emphasize the availability and analyze the importance of a fine device structure, fluorescence efficiency, material proportion, and integration position for performance improvement. The unique energy level structure arising from the 4fn inner shell configuration of the trivalent rare-earth ions gives multifarious options for efficient light-harvesting by upconversion and downconversion. Tandem or graded PSCs by combining a series of subcells with varying bandgaps seek to rectify the spectral mismatch. Plasmonic nanostructures function as a secondary light source to augment the light-trapping within the perovskite layer and carrier transporting layer, enabling enhanced carrier generation. Texturing the interior using controllable micro/nanoarrays can realize light-matter interactions. Anti-reflective coatings on the top glass cover of the PSCs bring about better transmission and glare reduction. Photon concentration through perovskite-based luminescent solar concentrators offers a path to increase efficiency at reduced cost and plays a role in building-integrated photovoltaics. Distinct from other published reviews, we here systematically and hierarchically present all of the photon management strategies in PSCs by presenting the theoretical possibilities and summarizing the experimental results, expecting to inspire future research in the field of photovoltaics, phototransistors, photoelectrochemical sensors, photocatalysis, and especially light-emitting diodes. We further assess the overall possibilities of the strategies based on ultimate efficiency prospects, material requirements, and developmental outlook.