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Room-temperature photoluminescence lifetime for the near-band-edge emission of (000 1 ˉ ) p-type GaN fabricated by sequential ion-implantation of Mg and H
摘要： Photoluminescence (PL) spectra of (000(cid:2)1) N-polar p-type GaN fabricated by using the sequential ion-implantation of Mg and H with subsequent high temperature annealing exhibited the near-band-edge (NBE) emission at 300 K. The longest PL lifetime (sPL) for the NBE emission of the sample with Mg and H concentrations of 1 (cid:2) 1019 and 2 (cid:2) 1020 cm(cid:3)3, respectively, annealed at 1230 (cid:4)C was 18 ps at 300 K. This value is almost comparable to that of the (0001) Ga-polar p-type Mg-doped GaN (p-GaN:Mg) homoepitaxial ?lm of the same Mg concentration. By correlating sPL and the concentration of major vacancy-type defects quanti?ed using positron annihilation spectroscopy, the electron capture-cross-section (rn) of the major nonradiative recombination centers (NRCs), namely, clusters of Ga vacancies (VGas) and N vacancies (VNs) such as (VGa)3(VN)3, is estimated at a few times 10(cid:3)13 cm2. This rn value is also comparable to that of the major NRCs in p-GaN:Mg epilayers, namely, VGa(VN)2 or VGa(VN)3, although the clustering sizes of the defects are different. These rn values are commonly larger than the hole capture-cross-section (rp ? 7 (cid:2) 10(cid:3)14 cm2) of the major NRCs, VGaVN divacancies, in n-type GaN.
关键词： p-type GaN,ion-implantation,Mg and H,electron capture-cross-section,photoluminescence,nonradiative recombination centers
更新于2025-09-23 15:21:21
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An Effective Method for Recovering Nonradiative Recombination Loss in Scalable Organic Solar Cells
摘要： Regarded as a critical step in commercial applications, scalable printing technology has become a research frontier in the field of organic solar cells. However, inevitable efficiency loss always occurs in the lab-to-manufacturing translation due to the different fabrication processes. In fact, the decline of photovoltaic performance is mainly related to voltage loss, which is mainly affected by the diversity of phase separation morphology and the chemical structures of photoactive materials. Fullerene derivative indene-C60 bisadduct (ICBA) is introduced into a PBDB-T-2F:IT-4F system to control the active layer morphology during blade-coating process. Accordingly, as a symmetrical fullerene derivative, ICBA can regulate the crystallization tendency and molecular packing orientation and suppress charge carrier recombination. This ternary strategy overcomes the morphology issues caused by weaker shear impulse in blade-coating process. Benefiting from the reduced nonradiative recombination loss, 1.05 cm2 devices are fabricated by blade coating with a power conversion efficiency of 13.70%. This approach provides an effective support for recovering the voltage loss during scalable printing approaches.
关键词： nonradiative recombination loss,organic solar cells,large-area solar cells,blade coating
更新于2025-09-23 15:21:01
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Decreasing Energy Loss and Optimizing Band Alignment for High Performance CsPbI3 Solar Cells through Guanidine Hydrobromide Post-Treatment
摘要： On account of the superior thermal stability and applicable band gap (~ 1.7 eV), the inorganic halide CsPbI3 perovskite solar cells (PSCs) have aroused intense interest in recent years. Nevertheless, the CsPbI3 PSCs are still facing a problem of high energy loss (Eloss) which leads to low open-circuit voltage (VOC). Herein, we developed efficient CsPbI3 PSCs through guanidine hydrobromide (GABr) post-treatment on the surface of CsPbI3 film. After optimizing, a supreme power conversion-efficiency (PCE) of 18.02% was obtained, which was higher than the original one (16.58%). By further studying, the characterization of passivation was found, which led to the reduced nonradiative recombination rate. Besides, the band alignment between CsPbI3 and interface layer is also optimized, leading to the decreased electron transport barrier for electron collection, and superb hole contact for furnishing a driving force in the hole transferring and forbidding electron to flow in the opposite direction.
关键词： energy loss,GABr,nonradiative recombination,CsPbI3,band alignment
更新于2025-09-23 15:21:01
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Temperature dependence of nonradiative recombination processes in UV-B AlGaN quantum well revealed by below-gap excitation light
摘要： Nonradiative recombination (NRR) processes through defect states and their temperature dependence in UV-B AlGaN MQW sample on sapphire substrate grown by MOCVD technique have been studied by photoluminescence (PL) spectroscopy. We detected NRR centers by adding a below-gap excitation light with photon energies from 0.93 eV to 1.46 eV on an above-gap excitation light of 4.66 eV. All the BGE energies decreased PL intensity at 25 K, and the most-distinct quenching is observed by 1.27 eV BGE at the same BGE photon number density. The temperature-dependent PL intensity for the BGE energy of 1.27 eV is interpreted by three NRR centers. The one-level model dominates over that of two-level model in the temperature range 58 K < T < 88 K. The two-level model prevails in other region of temperature. The combination of one-level and two-level models is consistent with the spectral peak-energy shift as a function of temperature.
关键词： AlGaN,Quantum well,Two-wavelength excited photoluminescence,Recombination model,Nonradiative recombination center
更新于2025-09-23 15:19:57
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Evaluating the role of phenethylamine iodide as a novel anti-solvent for enhancing performance of inverted planar perovskite solar cells
摘要： Inverted perovskite solar cells (PSCs) have attracted much interest due to their improved operational stability in the past few years. However, despite the recent advances of their performance, they still suffer from low power conversion efficiencies with a reduced open-circuit voltage (Voc), as compared to PSCs with a regular structure, due to the presence of defect states. In this work, a promising and more effective strategy than the typical post-treatment passivation method is demonstrated for the decrease of nonradiative recombination in quadruple-cation RbCsMAFA inverted PSCs, through the employment of phenethylammonium iodide in the anti-solvent deposition step during the perovskite formation. As a result, a Voc value as high as 1.17 V is achieved, while control devices (where the typical chlorobenzene anti-solvent was used) exhibited a significantly lower Voc of 1.09 V. Additionally, the devices exhibited high moisture stability by maintaining nearly 80% of their initial efficiency for over 500 h exposure in ambient conditions.
关键词： efficiency,nonradiative recombination,perovskite solar cells,passivation,PEAI
更新于2025-09-23 15:19:57
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Simulation of perovskite solar cell temperature under reverse and forward bias conditions
摘要： We have developed a model to calculate the temperature of an illuminated perovskite solar cell (PSC) under the forward bias and that of a shaded one under the reverse bias at di?erent ambient conditions. The results show that the dissipated power due to the reverse bias (PRB) should be more than around 6 W to have a higher temperature in the shaded solar cell than that in the illuminated solar cell at the solar irradiance of 1000 W=m2, and this result is almost ambient temperature and wind velocity independent. It is also found that the generated thermal power due to the nonradiative recombination (PRec) becomes signi?cant at the open circuit voltage (Voc) condition, leading to illuminated solar cell temperature (Tcr) higher than that at the short circuit current (Jsc) condition by about 12.7 K, 13.3 K, and 13.9 K at the ambient temperatures of 270 K, 300 K, and 330 K, respectively. In addition, the in?uence of the thickness of the illuminated solar cell on its temperature at the Voc condition is investigated, which reveals that, by increasing the thickness from 100 nm to 300 nm, the solar cell temperature can increase by 20 K.
关键词： temperature,nonradiative recombination,perovskite solar cell,reverse bias,forward bias
更新于2025-09-19 17:13:59
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Soft Lattice and Defect Covalency Rationalize Tolerance of ?2a??CsPbI3 Perovskite Solar Cells to Native Defects
摘要： Although all-inorganic lead halide perovskite solar cells have shown tremendous improvement over the past few years, they are still inferior to the hybrid organic-inorganic perovskites in the solar power conversion efficiency. Recently, a conceptually new β-CsPbI3 perovskite has demonstrated an impressive 18.4% efficiency combined with good thermodynamic stability at ambient conditions. We use ab initio non-adiabatic molecular dynamics to show that native point defects in β-CsPbI3 are generally benign for nonradiative charge recombination, regardless of whether they introduce shallow or deep trap states. Moreover, formation of new covalently bound species in the presence of defects slows down the recombination. These results indicate that halide perovskites do not follow the simple models used to explain defect-mediated charge recombination in the conventional semiconductors. The strong tolerance of electron-hole recombination against defects arises due to the softness of the perovskite lattice, which permits separation of electrons and holes upon defect formation, and allows only low-frequency vibrations to couple to the electronic subsystem. Both factors decrease significantly the non-adiabatic coupling and slow down the dissipation of electronic energy to heat. We suggest that a halide-rich synthesis environment may further improve the efficiency, and propose that strong defect tolerance is general to metal halide perovskites because they exhibit much lower bulk moduli compared to the conventional semiconductors used in photovoltaic, photocatalytic, electrocatalytic, lasing, light-emitting, detecting and other opto-electronic devices.
关键词： Electron-phonon coupling,Nonradiative recombination,All-inorganic perovskites,Time-dependent density functional theory,Defects
更新于2025-09-19 17:13:59
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Auger Recombination in Quantum Well Laser with Participation of Electrons in Waveguide Region
摘要： A new mechanism of nonradiative recombination of nonequilibrium carriers in semiconductor quantum wells is suggested and discussed. For a studied Auger recombination process the energy of localized electron-hole pair is transferred to barrier carriers due to Coulomb interaction. The analysis of the rate and the coefficient of this process is carried out. It is shown, that there exists two processes of thresholdless and quasithreshold types, and thresholdless one is dominant. The coefficient of studied process is a non-monotonous function of quantum well width having maximum in region of narrow quantum wells. Comparison of this process with CHCC process shows that these two processes of nonradiative recombination are competing in narrow quantum wells, but prevail at different quantum well widths.
关键词： waveguide region,Auger recombination,nonradiative recombination,quantum well laser,semiconductor
更新于2025-09-16 10:30:52
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Solvent engineering of LiTFSI towards high-efficiency planar perovskite solar cells
摘要： The performance and stability of perovskite solar cell (PSC) are inseparable from the quality of perovskite film, and the solvent engineering is being seemed as an effective strategy to enhance the properties of perovskite. Acetonitrile (ACN) is often used as a solvent to dissolve bis(trifluoromethane)sulfonimide lithium salt (LiTFSI), but ACN can corrode the perovskite film, which hinders the promotion of PSC efficiency and durability. Herein, a solvent engineering approach is implemented to search for suitable alternatives for ACN to abate the degradation of the perovskite films. The results demonstrate that isopropanol (IPA) with smaller polarity can effectively dissolve LiTFSI and slow down the degradation of the perovskite layer compared with ACN, which can result in the reduction of defects as well as the nonradiative recombination. Consequently, the devices using LiTFSI/IPA as additive achieve superior power conversion efficiencies (PCEs) with relatively less hysteresis effects and get a champion PCE of 19.43%, while the device using LiTFSI/ACN gets an inferior PCE of 17.12%.
关键词： Trap density,Nonradiative recombination,Solvent engineering,Isopropanol,Perovskite solar cells
更新于2025-09-16 10:30:52
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Non-radiative recombination at dislocations in InAs quantum dots grown on silicon
摘要： We study the impact of misfit dislocations on the luminescence from InAs quantum dots (QDs) grown on Si substrates. Electron channeling contrast imaging is used together with cathodoluminescence mapping to locate misfit dislocations and characterize the resulting nonradiative recombination of carriers via near-infrared light emission profiles. With a 5 kV electron beam probe, the dark line defect width due to a typical misfit dislocation in a shallow QD active layer is found to be approximately 1 lm, with a 40%–50% peak emission intensity loss at room temperature. Importantly, we find that at cryogenic temperatures, the dislocations affect the QD ground state and the first excited state emission significantly less than the second excited state emission. At the same time, the dark line defect width, which partially relates to carrier diffusion in the system, is relatively constant across the temperature range of 10 K–300 K. Our results suggest that carrier dynamics in the QD wetting layer control emission intensity loss at dislocations, and that these defects reduce luminescence only at those temperatures where the probability of carriers thermalizing from the dots into the wetting layer becomes significant. We discuss the implications of these findings toward growing dislocation-tolerant, reliable quantum dot lasers on silicon.
关键词： silicon substrates,nonradiative recombination,quantum dot lasers,InAs quantum dots,cathodoluminescence,misfit dislocations
更新于2025-09-16 10:30:52