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Utilizing first-principles calculations, this study explores the physical characteristics of K2BGaI6 (B = Tl, Rb) double perovskites with the objective of gaining a deeper understanding of their viability for renewable applications. In evaluating the phase stability, we calculated the formation enthalpies, tolerance factor and optimization energies, demonstrating that both compounds exhibit stability and are conducive to experimental synthesis. The semiconducting nature of perovskites is manifested through an energy gap, with values of 1.11 eV at (L–X) for K2TlGaI6 and 1.2 eV at (L–L) for K2RbGaI6, which is also reflected from density of states. Both perovskites display ductile characteristics, but the hardness factor indicates greater strength for K2RbGaI6. The Kleinman parameter value for K2RbGaI6 and K2TlGaI6 indicates a prevalence of bond stretching. The Debye and melting temperatures of K2RbGaI6 surpass that of K2TlGaI6. The assessment of optical response involves examining various parameters that reveal absorption in both the visible and UV regions. The thermoelectric response is gauged by examining prominent values in electrical conductivity, Seebeck, and ZT parameters at high elevated temperatures. The collective findings favor the utilization of K2BGaI6 (B = Tl, Rb) perovskites in environmentally friendly technologies. [ABSTRACT FROM AUTHOR]

The switch to sustainable power generation sources has gained substantial spotlight due to the essential need to decrease fossil fuels dependence, and alleviate climate change issues. This research aims to explore the first principle calculations for geometrical structure, enthalpy of formation, electronic structure behavior, optical spectra, and photocatalytic performance of the clean new Iodine-based triple perovskite compounds A3B2I9 (A = Rb or Cs, and B = Sb or Bi) using FP-LAPW method based on the density functional theory implemented in Wien2K software. The outcomes prove that these triple perovskite compounds can be formed spontaneously under standard conditions, because they are thermodynamically stable. Moreover, the electronic band structure shows an indirect semiconductor behavior of all studied compounds. Further, the optical spectra highlights that all studied compounds have high visible light absorption due to their suitable forbidden band values [1.8 eV–2.369 eV] which facilitate efficient electron–hole pairs generation maximizing the conversion of light into electrical energy. In addition, all studied compounds are satisfied the limits necessary to split water and then to produce hydrogen. Consequently, these compounds are most likely to be used as Lead-free perovskites in various optoelectronic applications, especially solar cells and hydrogen production from water splitting. [ABSTRACT FROM AUTHOR]

Perovskite-type lead halides exhibit promising performances in optoelectronic applications, for which lasers are one of the most promising applications. Although the bulk structure has some advantages, perovskite has additional advantages at the nanoscale owing to its high crystallinity given by a lower trap density. Although the nanoscale can produce efficient light emission, its comparatively poor chemical and colloidal stability limits further development of devices based on this material. Nevertheless, bulk perovskites are promising as optical amplifiers. There has been some developmental progress in the study of optical response and amplified spontaneous emission (ASE) as a benchmark for perovskite bulk phase laser applications. Therefore, to achieve high photoluminescence quantum yields (PLQYs) and large optical gains, material development is essential. One of the aspects in which these goals can be achieved is the incorporation of a bulk structure of high-quality crystallization films based on inorganic perovskite, such as cesium lead halide (CsPb(Br/Cl)3), in polymethyl methacrylate (PMMA) polymer and encapsulation with the optimal thickness of the polymer to achieve complete surface coverage, prevent degradation, surface states, and surface defects, and suppress emission at depth. Sequential evaporation of the perovskite precursors using a single-source thermal evaporation technique (TET) effectively deposited two layers. The PL and ASEs of the bare and modified films with a thickness of 400 nm PMMA were demonstrated. The encapsulation layer maintained the quantum yield of the perovskite layer in the air for more than two years while providing added optical gain compared to the bare film. Under a picosecond pulse laser, the PL wavelength of single excitons and ASE wavelength associated with the stimulated decay of bi-excitons were achieved. The two ASE bands were highly correlated and competed with each other; they were classified as exciton and bi-exciton recombination, respectively. According to the ASE results, bi-exciton emission could be observed in an ultrastable CsPb(Br/Cl)3 film modified by PMMA with a very low excitation energy density of 110 µJ/cm2. Compared with the bare film, the ASE threshold was lowered by approximately 5%. A bi-exciton has a binding energy (26.78 meV) smaller than the binding energy of the exciton (70.20 meV). [ABSTRACT FROM AUTHOR]

Perovskite halide has many advantages that attracted the attention of researchers in the last years, but many challenges prevent the use of halide perovskites in different applications. One of these challenges is the low thermal stability resulting in phase transitions with temperatures. Here, the photoluminescence (PL) characteristics and related phase transitions of different CH3NH3Pb(BrxI1−x)3 (MA(BrxI1−x)3)3 perovskites structures have been investigated under a wide temperature range. The work that has been conducted demonstrates that under temperature, the exciton behavior of the halide anions, I and Br, has a considerable impact on structural phases and the fluorescence process. The obtained results for the temperature dependence of PL for MAPb(BrxI1−x)3 showed a wide range of emission wavelengths, between 500–800 nm with a decrease in PL intensity with increasing temperature. In addition, the ratio of both bromine and iodine in MAPb(BrxI1−x)3 affects the range of phase transition temperatures, where at x = 0.00, 0.25, and 0.50 the first transition occurs below room temperature (orthorhombic to tetragonal) phase and the other occurs above room temperature (tetragonal to cubic) phase. Furthermore, increasing the proportion of bromine causes all the transitions to occur below room temperature. The presented findings suggest a suitable halide component under a temperature-controlled phase transformation to benefit these materials in photonics devices. [ABSTRACT FROM AUTHOR]

Controlling the crystallinity, homogeneity, and surface morphology is an efficient method of enhancing the perovskite layer. These improvements contribute toward the optimization of perovskite film morphology for its use in high-performance photovoltaic applications. Here, different solvents will be used in order to process the perovskite precursor, to improve the interfacial contacts through generating a smooth film and uniform crystal domains with large grains. The effect that the solvent has on the optical and structural properties of spin-coated methyl ammonium lead iodide (MAPbI3) perovskite thin films prepared using a single-step method was systematically investigated. The spin-coating parameters and precursor concentrations of MAI and PbI2 were optimized to produce uniform thin films using the different solvents N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and γ-butyrolactone (GBL). The effect that the solvent has on the morphology of the MAPbI3 films was examined to determine how the materials can be structurally altered to make them highly efficient for use in perovskite hybrid photovoltaic applications. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) results show that the synthesized MAPbI3 films prepared using DMSO, DMF, and GBL exhibit the best crystallinity and optical characteristics (photoluminescence (PL)), respectively, of the prepared films. The optical properties resulting from the noticeable improvement PL of the films can be clearly correlated with their crystallinity, depending on the solvents used in their preparation. The film prepared in DMSO shows the highest transmittance and the highest bandgap energy of the prepared films. [ABSTRACT FROM AUTHOR]

The high crystal quality of formamidium lead bromide perovskite (CH(NH2)2PbBr3 = FAPbBr3) was infiltrated in a mesoporous TiO2 network. Then, high-quality FAPbBr3 films were evaluated as active lasing media, and were irradiated with a picosecond pulsed laser to demonstrate amplified spontaneous emission (ASE), which is a better benchmark of its intrinsic suitability for gain applications. The behavior was investigated using two excitation wavelengths of 440 nm and 500 nm. Due to the wavelength-dependent absorbance spectrum and the presence of a surface adsorption layer that could be reduced using the shorter 440 nm wavelength, the ASE power dependence was strongly reliant on the excitation wavelength. The ASE state was achieved with a threshold energy density of ~200 µJ/cm2 under 440 nm excitation. Excitation at 500 nm, on the other hand, needed a higher threshold energy density of ~255 µJ/cm2. The ASE threshold carrier density, on the other hand, was expected to be ~4.5 × 1018 cm−3 for both excitations. A redshift of the ASE peak was detected as bandgap renormalization (BGR), and a BGR constant of ~5–7 × 10−9 eV cm was obtained. [ABSTRACT FROM AUTHOR]

Photonic devices based on perovskite materials are considered promising alternatives for a wide range of these devices in the future because of their broad bandgaps and ability to contribute to light amplification. The current study investigates the possibility of improving the light amplification characteristics of CsPbBr3 perovskite quantum dot (PQD) films using the surface encapsulation technique. To further amplify emission within a perovskite layer, CsPbBr3 PQD films were sandwiched between two transparent layers of poly(methyl methacrylate) (PMMA) to create a highly flexible PMMA/PQD/PMMA waveguide film configuration. The prepared perovskite film, primed with a polymer layer coating, shows a marked improvement in both emission efficiency and amplified spontaneous emission (ASE)/laser threshold compared with bare perovskite films on glass substrates. Additionally, significantly improved photoluminescence (PL) and long decay lifetime were observed. Consequently, under pulse pumping in a picosecond duration, ASE with a reduction in ASE threshold of ~1.2 and 1.4 times the optical pumping threshold was observed for PQDs of films whose upper face was encapsulated and embedded within a cavity comprising two PMMA reflectors, respectively. Moreover, the exposure stability under laser pumping was greatly improved after adding the polymer coating to the top face of the perovskite film. Finally, this process improved the emission and PL in addition to enhancements in exposure stability. These results were ascribed in part to the passivation of defects in the perovskite top surface, accounting for the higher PL intensity, the slower PL relaxation, and for about 14 % of the ASE threshold decrease. [ABSTRACT FROM AUTHOR]

High-quality inorganic cesium lead halide perovskite CsPb(Br0.5Cl0.5)3 thin films were successfully achieved through evaporation of the precursors and deposition sequentially by a single-source thermal evaporation system. The different melting points of the precursors were enabled us to evaporate precursors one by one in one trip. The resulting films through its fabrication were smooth and pinhole-free. Furthermore, this technique enabled complete surface coverage by high-quality perovskite crystallization and more moisture stability oppositely of that produce by solution-processed. Then the perovskite films were encapsulated by evaporated a polymethyl methacrylate (PMMA) polymer as a specialized surface passivation approach with various thicknesses. The blue emission, high photoluminescence quantum yield (PLQY), stable, and low threshold of amplified spontaneous emission (ASE) properties of CsPb(Br0.5Cl0.5)3 films in the bulk structure at room temperature were achieved. The effects of the surface-passivation layer and its thickness on the optical response were examined. Detailed analysis of the dependence of ASE properties on the surface passivation layer thickness was performed, and it was determined this achieves performance optimization. The ASE characteristics of bare perovskite thin film were influenced by the incorporation of the PMMA with various thicknesses. The improvement to the surface layer of perovskite thin films compared to that of the bare perovskite thin film was attributed to the combination of thermal evaporation deposition and surface encapsulation. The best results were achieved when using a low PMMA thickness up to 100 nm and reducing the ASE threshold by ~11 μJ/cm2 when compared with free-encapsulation and by ~13 μJ/cm2 when encapsulation occurs at 200 nm or thicker. Compared to the bare CsPb(Br0.5Cl0.5)3, ASE reduced 1.1 times when the PMMA thickness was 100 nm. [ABSTRACT FROM AUTHOR]

Organic–inorganic halide organometal perovskites have demonstrated very promising performance in optoelectronic applications, but their relatively poor chemical and colloidal stability hampers the further improvement of devices based on these materials. Perovskite material engineering is crucial for achieving high photoluminescence quantum yields (PLQYs) and long stability. Herein, these goals are attained by incorporating bulk-structure CsPbBr3, which prevents colloidal degradation, into polymethyl methacrylate (PMMA) polymer in thin-disk form. This technology can potentially realize future disk lasers with no optical and structural contributions from the polymer. The polycrystalline CsPbBr3 perovskite particles were simply obtained by using a mechanical processing technique. The CsPbBr3 was then incorporated into the PMMA polymer using a solution blending method. The polymer enhanced the PLQYs by removing the surface trap states and increasing the water resistance and stability under ambient conditions. In our experimental investigation, the CsPbBr3/PMMA composites were extraordinarily stable and remained strongly luminescent after water immersion for three months and air exposure for over one year, maintaining 80% of their initial photoluminescence intensity. The CsPbBr3/PMMA thin disk produced amplified spontaneous emission for a long time in air and for more than two weeks in water. [ABSTRACT FROM AUTHOR]

The effect of halide composition on the structural, electronic, and optical properties of CsPb(Br1−xClx)3 perovskite was investigated in this study. When the chloride (Cl) content of x was increased, the unit cell volume decreased with a linear function. Theoretical X-ray diffraction analyses showed that the peak (at 2θ = 30.4°) shifts to a larger angle (at 2θ = 31.9°) when the average fraction of the incorporated Cl increased. The energy bandgap (Eg) was observed to increase with the increase in Cl concentration. For x = 0.00, 0.25, 0.33, 0.50, 0.66, 0.75, and 1.00, the Eg values calculated using the Perdew–Burke–Ernzerhof potential were between 1.53 and 1.93 eV, while those calculated using the modified Becke−Johnson generalized gradient approximation (mBJ–GGA) potential were between 2.23 and 2.90 eV. The Eg calculated using the mBJ–GGA method best matched the experimental values reported. The effective masses decreased with a concentration increase of Cl to 0.33 and then increased with a further increase in the concentration of Cl. Calculated photoabsorption coefficients show a blue shift of absorption at higher Cl content. The calculations indicate that CsPb(Br1−xClx)3 perovskite could be used in optical and optoelectronic devices by partly replacing bromide with chloride. [ABSTRACT FROM AUTHOR]

The triplet energy transfer mechanism of novel poly(9,9-di-n-octylflourenyl-2,7-diyl) (PFO)/poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/CsPbBr3 perovskite quantum dot (PQD) hybrid thin films was comprehensively investigated. The concentrations of PFO and MEH-PPV in all the specimens were fixed, while the PQD content was varied with various weight ratios and premixed by a solution blending method before it was spin-coated onto glass substrates. The triplet non-radiative Förster resonance energy transfers (FRETs) in the PFO/MEH-PPV/PQDs ternary blend, the dual FRET from PFO to both PQDs and MEH-PPV, and the secondary FRET from PQDs to MEH-PPV were observed. The values of the Förster radius (Ro) of FRET from PFO to MEH-PPV in the presence of various PQD contents (Case I) increased from 92.3 to 104.7 Å, and they decreased gradually from 68.0 to 39.5 Å for FRET from PFO to PQDs in the presence of MEH-PPV (Case II). These Ro values in both cases confirmed the dominance of FRET in ternary hybrid thin films. Upon increasing the PQD content, the distance between the donor and acceptor molecules (RDA) and the conjugation length (Aπ) in both cases gradually decreased. The small values of Ro, RDA, and Aπ with a decrease in the energy transfer lifetime (τET) due to an increase in the PQD contents in both Cases I and II confirmed the efficient FRET in the hybrid. To prevent intermolecular transfer in PFO, the concentrations of MEH-PPV (Case I) and PQDs (Case II) should be decreased to a range of 0.57–0.39 mM and increased in the range of 1.42–7.25 mM. [ABSTRACT FROM AUTHOR]

The distinctive electronic characteristics of half-metallic materials make them exceptional as they pave the way for innovations in spintronics and other magnetic fields. We predict the ferromagnetism in half-metallic K 2 CeB'X 6 (B' = Ag, Cu & X = Cl, Br) perovskite halides by employing the spin-polarized computations. The tolerance factor, formation energies and optimization plots favor the structural stability of all perovskites. The K 2 CeB'X 6 (B' = Ag, Cu & X = Cl, Br) are half-metallic with a direct band gap of 2.59 eV, 2.53eV and 1.05eV, respectively, in the spin-down state, while the spin-up exhibit metallic character. The magnetic behavior is confirmed by the magnetic moment values. Several parameters for optical response are computed, showing the absorption in the visible and high energy spectrum. The spin-polarized response in terms of thermoelectric characteristics shows outstanding results. We have achieved the highest ZT values in spin-dn channel, which is unity for K 2 CeAgCl 6 , K 2 CeAgBr 6 and 0.98 for K 2 CeCuCl 6 at 300K. These values are continued even at higher temperatures with no significant change. The half-metallic characteristics with excellent thermoelectric attributes in the spin-dn channel provide the evidence to utilize these perovskites for spintronics and green technologies. • The spin-polarized calculation are performed to study the physical properties of K 2 Ce B ' X 6 (B ' = Ag, Cu & X = Cl,Br). • The stability is evaluated through negative formation energies and Goldsmith tolerance factor. • A half metallic nature of all structures is confirmed through the electronic band structures. • An optical band gap with maximum absorption is achieved for these compounds. • The thermoelectric characteristics shows outstanding results with highest ZT values in spin-dn channel. [ABSTRACT FROM AUTHOR]

Magnetic double perovskites have garnered significant interest due to their unique magnetic properties and are promising candidates for various spintronic applications. Spin-polarized method is used to investigate the physical attributes of magnetic cubic double perovskites Cs 2 XCeI 6 (X = Li, Na) using density functional theory. Elastic constants and mechanical properties are evaluated to assess the mechanical stability of studied perovskites. The confirmation of the structure stability is accomplished via formation and cohesive energies, optimization plots, octahedral tilting and tolerance factor. Electronic properties revealed that Cs 2 LiCeI 6 possess an indirect bandgap of 2.06 eV and 2.43 eV in spin up and down channels, and Cs 2 NaCeI 6 have an indirect bandgap of 2.30eV and 2.64 eV in spin up and down channels, respectively. The computed magnetic moment for both perovskites is reported as 1 μ B. Kramers-Kronig complex equations are used to analyze the optical behavior. The peak absorption in the UV range is revealed with minimal energy loss for both perovskites. The maximum peaks for optical conductivity and extinction coefficient also observed in UV spectrum. According to an analysis of the derived properties, optoelectronics and spintronic are two areas for which these double perovskites are well suited. [ABSTRACT FROM AUTHOR]

In this study, we present the effect of doping with antimony trisulfide (Sb 2 S 3) nanobare on the electrical, optical, structural, and morpholigcal properties of CH 3 NH 3 PbI 3 perovskite thin films. Doped with Sb 2 S 3 nanobare, the thin coatings demonstrated an exceptionally high degree of purity, featuring a tetragonal phase within its single-phase structure. This allowed for the creation of (110) textured CH 3 NH 3 PbI 3 films, which comprised micrometer-sized grains arranged in a vertical direction across the entire film thickness and featured high crystallinity. Additionally, the CH 3 NH 3 PbI 3 perovskites films exhibited significant optical absorption at appropriate energy levels and exhibited a high gachin rate of photons. Substance doping methods that can optimize the morphology of the perovskite active layer with large granules are exceedingly desirable in order to reduce charge carrier recombination. The synthesis of perovskite films with dimensions on the order of microns can be achieved by incorporating a regulated quantity of Sb 2 S 3 nanobare into the precursor solution. The incorporation of these textured CH 3 NH 3 PbI 3 :Sb 2 S 3 nanobare films significantly enhanced the power conversion efficiency (PCE) of the perovskite solar cells. The solar cell device configuration utilized in this investigation is as follows: glass/FTO/TiO 2 /CH 3 NH 3 PbI 3 :Sb 2 S 3 nanobars/spiro-OMeTAD/Au. By employing Sb 2 S 3 nanobars at a concentration of 9 mg/mL, we successfully attained an exceptional power conversion efficiency of 15.87 %. The resulting values for these parameters include an open-circuit voltage V OC of 1.09 V, a short-circuit current density J SC of 21.15 mA/cm2, and a fill factor FF of 68.87 %. • Sb 2 S 3 nanobars -doped CH 3 NH 3 PbI 3 perovskite-based solar cells are optimized for increased efficiency. • The effect of the Sb 2 S 3 nanobars on the structural, optical, and solar cell performance was studied. • Sb 2 S 3 nanobars affect carrier transport, surface roughness, crystallinity, and light absorption. • Optimal power conversion efficiency of 15.87 % was achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • The structural, elastic, electronic, transport, and optical properties of lead-free double perovskites K 2 CuBiX 6 (where X can be I, Br, or Cl) have been thoroughly examined through first-principles calculations. • The electronic band structure shows an increment in the energy gap after the replacement of Iodine with Bromine and Chlorine, which is also endorced by the density of states (DOS). An optical band gap with large absorption in the visible and UV region reveal the potential of K 2 CuBiX 6 (X = I, Br, Cl) for the applications in optoelectronics. • The perovskites exhibit substantial potential for renewable energy applications, as they demonstrate significant ZT values, which suggest their availability for thermoelectric devices. Potassium-based perovskites hold significant potential to revolutionize renewable technology by enabling more cost-effective and sustainable energy devices. The DFT incorporated in the Wein2K interface is used to provide an extensive investigation of the structural, mechanical, electrical, optical, and thermoelectric behavior of double perovskites K 2 CuBiX 6 (X = I, Br, Cl). Structural stability is confirmed through optimization curves, tolerance factor and octahedral tilting. Mechanical properties support the ductile character of K 2 CuBiX 6 (X = I, Br, Cl). Electronic band structures reveal that perovskite K 2 CuBiI 6 initially possesses a bandgap of 0.6 eV. This bandgap is increased to 0.97 eV when (I) atom is replaced with (Br) atom. Furthermore, a prominent shift in the bandgap value occurs when the bromine (Br) atom is replaced with a chlorine (Cl) atom, resulting in a bandgap of 1.3 eV. The Kramer-Kronig equations are used to evaluate the optical characteristic, which shows significant absorption in the visible range for all structures, allowing them to be utilized in optoelectronics. Numerous thermoelectric characteristics are calculated using the Boltzmann semi-classical theory. The perovskites exhibit substantial potential for renewable energy applications, as they demonstrate significant ZT values, along with elevated Seebeck coefficients and electrical conductivities, which enhance their suitability for utilization in clean energy technologies. [ABSTRACT FROM AUTHOR]

The crystallization techniques of organic-inorganic hybrid perovskites (OIHP) are considered an effective method for light collector or light emitting applications. In this article, the optical band gap, electron-hole behavior, and energy band alignment are all key optoelectronic properties of crystalline perovskite structures studied in this study. For this reason, a perovskite solution was prepared in a single step and tetrahydrofuran (THF) was used as a solvent to dissolve both perovskite precursors. Rapid crystallization of perovskite in solution was observed, preventing the formation of homogenous perovskite thin films. Subsequently, the effect of THF solvent on the direct crystallization of MAPbI 3 perovskite without thermal annealing was investigated. Thermal annealing is considered necessary for perovskite crystal formation as it gives the molecules enough thermal energy to self-organize and form a well-ordered crystalline layer. The procedures that create perovskite crystals without thermal annealing give a novel method for room temperature film preparation (RT) and pave the way for the manufacture of low-cost, stable perovskite solar cells (PSCs). UV–vis absorption/reflectance, photoluminescence, XRD, and SEM were used to explore the effects of this approach on the optical and structural properties of MAPbI 3 perovskite thin films. • Crystallizing Growth of MAPbI 3 Perovskite Nanorod was demonstrated. • Perovskite precursor solution in THF is dried to form perovskite powder. • Fabrication of perovskite films without annealing. • Perovskite films were tested under ns laser. • The strong light emission allows the observation of ASE. [ABSTRACT FROM AUTHOR]

In this paper, we present a study of the structural and optical properties of organic–inorganic halide-based perovskite semiconductors with band gaps varying from NIR to visible at room temperature. Thin films of nanocrystalline CH 3 NH 3 PbI 3 with different concentrations of methylammonium iodide (MAI) have been successfully deposited onto glass substrates using single step spin-coating technique. The prepared films have been characterized by X-ray diffraction, optical absorption spectroscopy and photoluminescence measurements. X-ray diffraction scans revealed that even for stoichiometric atomic concentrations of MA:Pb:I of 1:1:3, the PbI 2 phase was also present. The PbI 2 phase showed a highly textured along the (001) direction in all the prepared films, with a crystallite size in the range of approximately 30–40 nm. The optical absorbance edge of CH 3 NH 3 PbI 3 thin films is described in terms of direct transition model proposed by Tauc in the strong absorption region. The band gap of the pure PbI 2 film was calculated to be 2.40 eV, whereas the band gap of the pervoskite film with stoichiometric ionic ratio of 1:1 PbI 2 and CH 3 NH 3 I was calculated to be 1.46 eV, while absorption coefficient is ~10 5 cm −1 . Photoluminescence measurements showed a red shift in the perovskite emission with increasing the MAI concentration, confirming the correct placement of the MA ions in the perovskite crystalline structure showing the PbI 2 octahedra. Our results confirm the existence of PbI 2 phase in the highly efficient perovskite solar cells, as demonstrated in the recent publication. [ABSTRACT FROM AUTHOR]