Carrier Capture Cross Sections Research Articles

Active Passivation of Anion Vacancies in Antimony Selenide Film for Efficient Solar Cells.

Binary antimony selenide (Sb2Se3) is a promising inorganic light-harvesting material with high stability, nontoxicity, and wide light harvesting capability. In this photovoltaic material, it has been recognized that deep energy level defects with large carrier capture cross section, such as VSe (selenium vacancy), lead to serious open-circuit voltage (VOC) deficit and in turn limit the achievable power conversion efficiency (PCE) of Sb2Se3 solar cells. Understanding the nature of deep-level defects and establishing effective method to eliminate the defects are vital to improving VOC. In this study, a novel directed defect passivation strategy is proposed to suppress the formation of VSe and maintain the composition and morphology of Sb2Se3 film. In particular, through systematic study on the evolution of defect properties, the pathway of defect passivation reaction is revealed. Owing to the inhibition of defect-assisted recombination, the VOC increases, resulting in an improvement of PCE from 7.69% to 8.90%, which is the highest efficiency of Sb2Se3 solar cells prepared by thermal evaporation method with superstrate device configuration. This study proposes a new understanding of the nature of deep-level defects and enlightens the fabrication of high quality Sb2Se3 thin film for solar cell applications.

Analysis of defects dominating carrier recombination in CeO2 single crystal for photocatalytic applications

In photocatalytic water splitting and CO2 reduction, recently, cerium oxide (CeO2) has been widely investigated. Defects that can directly dominate carrier recombination are essential for the photocatalytic performance of CeO2. In this study, several photoluminescence (PL) peaks are observed on the (100) face of an undoped CeO2 single crystal, indicating the presence of defects. Moreover, we characterize carrier recombination using time-resolved photoluminescence (TR-PL) and microwave photoconductivity decay (μ-PCD) measurements. The temperature dependence of decay curves is the result of carrier trapping and emission at deep levels. These decay curves are observed separately using a 565 nm band-pass filter (BPF) based on the PL spectra. The trap energy level ( ET ) and majority carrier capture cross-section ( σT ) of each defect are also analyzed using rate equations to fit the experimental results. The temperature-dependent time constants are well reproduced by a recombination model using hole traps HTinfrared and HTvisible at ET of 0.76 and 0.55 eV from the conduction or valence band, with estimated σT of the order of 10−21 and 10−22 cm2 for without and with the BPF, respectively. These findings regarding the presence of multiple defects in a single crystal indicate the necessity to focus on defect control.

Multilayers strategy with a mixed CdTe/ZnTe absorber layer for optical trapping and efficiency improvement in CdTe-based solar – SCAPS modelling

This work is a theoretical contribution to improving the performance of CdTe-based thin-film solar cells (TFSC) by optimising the collection of photons in the absorber structure. The basic data are retrieved from experimental reference work and the reference structure is as follows: CdS/CdTe/ZnTe with an efficiency of 20.16%, where ZnTe is used as a BSF to limit backward recombination. The first approach is to incorporate a ZnTe thin layer at the CdS/CdTe heterojunction, to subdivide the CdTe active layer into two (02) sub-layers and to identify the optimum structure as a function of their position in the stack. Investigating the work function of back contact materials enables to better enhance the device′s performance and stability. To take into consideration the discontinuities in the material properties, grain boundaries and performance loss factors, the impacts of charge carrier capture cross sections, bulk and interfacial defects are investigated. SCAPS software is employed for all the numerical modelling, which enables to calculate the current-voltage (J-V), power-voltage (P-V), external quantum efficiency (EQE) and other PV parameters and to draw energy band diagram to better appraise charge carrier transportation. The doping level in the CdTe active layer, the thicknesses and external temperature are also investigated to optimize our device properties. In terms of the obtained fill factor (FF) and efficiency (PCE), the performances were improved with the following structure CdS/CdTe/ZnTe/CdTe/ZnTe, FF = 81.6% and PCE = 23.45%, with 500 nm thickness of CdTe. These results are opening a promising new perspective in high efficiency CdTe TFSC.

Studies on the performance of FASnI3:Zn2+-based lead-free perovskite solar cells: A numerical simulation

The search of stable, lead-free absorber material for perovskite solar cells (PSC) resulted in many alternatives, particularly, zinc (Zn) doped formamidinium tin iodide (FASnI3). This work facilitates in investigating the behavior of four different Zn doping ratios 0 %, 2 %, 5 %, and 10 % (say Zn-0, Zn-2, Zn-5, and Zn-10) on the performance of FTO/PCBM/FASnI3:Zn2+/MoOx/Au solar cell structure. A precise evaluation on the impact of the four various Zn doping ratios in the mentioned solar structure in terms of thickness of perovskite absorber layer, hole transport layer, and electron transport layer were executed. The investigation through numerical study further deals with the role of interfacial defect density and capture cross-section of charge carriers on the performance of suggested PSCs with varying Zn doping ratios. It is evident from the optimization results that PSC having absorber layer thickness of 400 nm yields better power conversion efficiency (PCE) of 11.49 % for Zn-5. The PCE is further improved to 13.98 % for capture cross section of 2 ×10−15 cm2. The entire work witnessed distinguishable superior behavior from FASnI3-based PSC doped with Zn ratio: Zn-5 in comparison to the PSCs doped with other Zn ratios. Furthermore, impact of the series and shunt resistances on performance parameters are also examined.

Electric-Tree Resistant Performance and Thermal Charge-Carrier Dissipation Mechanism of Voltage Stabilizer-Modified EPDM

In order to improve electric-tree resistant performance and dielectric breakdown strength of ethylene-propylene-diene misch-polymere (EPDM) material used for cable accessory reinforce insulation, the two specific aromatic ketone compounds—vinylphenylacetone (VPE) and 4-propylene oxyxy-2-hydroxydibenzenone (AOHBP) are employed as two paradigms of voltage stabilizer for chemical-graft modifications. Electric-tree resistances and insulation performances of modified EPDM materials and their charge trapping mechanism of thermoelectron inhibitions are studied by the accelerated electric-tree aging experiments, alternating current (AC) dielectric breakdown tests, surface potential trap-level analyses and first-principles calculations. Both the two species of voltage stabilizers are effective for promoting electric-tree inception voltage and dielectric breakdown strength, leading to a high extension of electric-tree morphology and smaller dimension of electric-trees growth, in which AOHBP is more significant. The two species of voltage stabilizers have been successfully grafted onto EPDM molecular-chains in thermal-chemistry crosslinking reactions of EPDM, introducing multiple shallow levels of charge traps, which reduces the energy released by trapping charge carriers and thus alleviates electric-tree aging of EPDM. The AOHBP and VPE represent a high electron affinity and a small electronic energy gap, which is competent of assimilating the kinetic energies of hot charge carriers whilst restricting Auger electronic excitation. Especially, the benzene group in voltage stabilizer renders shallow level charge traps with a larger carrier capture cross-section than deep traps and simultaneously possesses the high atomic vibration frequencies similar as electronic-transition energies, which results in effective dissipation on the kinetic energies of hot charge carriers. This mechanism dominates to increase electric-tree resistance and insulation strength of EPDM. The present study proves the important role of voltage stabilizers in improving insulation performance of EPDM material, and reveals the refrigeration mechanism on hot charge carriers for restricting electric-tree growth, which provides a significant strategy of chemical modifications for developing high-insulation cable accessory materials.

Materials and interfaces properties optimization for high-efficient and more stable RbGeI3 perovskite solar cells: optoelectrical modelling

In this research work, we investigated the effects of a broad set of materials properties and external operating parameters on the opto-electrical output of a hybrid RbGeI3-based perovskite solar cell (PSC) as a means of enhancing its performance. We first performed a judicious numerical modelling of the reference cell with the following structure FTO/TiO2/RbGeI3/Spiro-OMeTAD/Ag, with data retrieved from the experiment. SCAPS program enables to model the device, considering charge carriers transport governing equations. Investigations are directed on addressing the current challenges that include thinner, less environmentally harmful, cost-effectiveness, and more stable solar devices over time. Analysis of the effects of different hole transport material (HTM) on current–voltage (J-V) and external quantum efficiency (QE) characteristics, helps to identify CuI as an ideal HTM. Optimal cell output were achieved by investigating the effects of metal contact work function, defect states, RbGeI3 thickness, light transmission/reflection at the front/back contact, as well as operating temperature. As a result, efficiency increased significantly from 10.11 to 18.10%, and fill factor that represents a stability indicator, increased from 63.68 to 76.95%. Moreover, an optimum open-circuit voltage Voc = 0.70 V and a high short-circuit current density of Jsc = 33.51 mA/cm2 were recorded. An additional study on the capture cross-section of charge carriers ({sigma }_{n,p}) on PV characteristics, enabled to achieve a power conversion efficiency (PCE) of 29.71% and FF of 88% at a value of {sigma }_{n,p} selected to be 10–22 cm2. This contribution aims at designing and producing thinner, more efficient, more stable and more environmentally clean and economically viable PSCs.

The modelling and simulation of perovskite solar cell consisting textile-based electrodes

Perovskite solar cell (PSC) consisting textile-based electrodes has been created novel features for future energy supply. Recently, Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 perovskite has appeared as a favourable candidate for flexible perovskite solar cells. However, a confined performance was acquired when the conventional Spiro-OMeTAD were used as hole transport layer (HTL) material because of suboptimal valance band offset (ΔEV) between Perovskite/HTL layers. In this study, a theoretical drift–diffusion​ modelling is used by finite volume method (FVM) to investigate performance of textile perovskite solar cell with double hole transport layers (HTLs) with graded band gap energies. Copper thiocyanate (CuSCN) and Nickel Oxide (NiO) are replaced as double HTLs, which dramatically enhanced the performance due to optimal upward step by step valance band offsets (ΔEV) between Perovskite/Textile Composite Electrode layers. It is shown that the decreasing of the metal–semiconductor schottky barrier height of electrodes leads to significant increase in fill factor (FF). Also, it is revealed that the enriching of perovskite carrier diffusion length by equipoising of carrier capture cross section, carrier total defect density and carrier thermal velocity substantially promote the overall device efficiency. The short-circuit current (Jsc) of 20.65 mA/cm 2, open-circuit voltage (Voc) of 1.19 V, fill factor (FF) of 73.57%, and power conversion efficiency (PCE) of 18.20% have been obtained by optimization of electrodes properties and perovskite layers. Remarkably, the advantageous of low cost, flexible, and chemical stable conducive textile composite, extends new opportunities in the commercial expansion of highly efficient photovoltaic textile in optoelectronic industry field.

Performance enhancement of Sb2Se3-based solar cell with hybrid buffer layer and MoSe2 as a hole transport material using simulator device

In this work, we first compared the experimental and simulated J-V characteristics of the Sb2Se3-based solar cell without and with a hybrid buffer layer using SCAPS-1D software. The introduction of a second buffer layer reduces the current leakage caused at the front contact of the solar cell and the power conversion efficiency (PCE) increases from 3.75% to 5.18%; and the use of the ternary compound cadmium zinc sulfide (CdZnS), as an alternative electron transport layer (ETL) to the traditional cadmium sulfide (CdS), increases the PCE from 5.18% to 7.13%. Thereafter, different thicknesses of the SnO2/CdZnS hybrid buffer layer were simulated, and the optimization resulted in a value of 50 nm, with thicknesses of 10 nm and 40 nm for the SnO2 and CdZnS layers respectively. Furthermore, the optimization of the Sb2Se3 absorber allows to obtain a bulk defect density of 1011 cm−3 and a carrier capture cross section of 10–14 cm2. Finally, the low doping problem of the absorber is solved by forming a MoSe2 layer at the Sb2Se3/Mo interface. MoSe2 acts as a hole transport material (HTM) and is used for high mobility of charge carriers within it; moreover, its presence improves the performance of the Sb2Se3-based solar cell and a PCE of 18.77% (JSC = 34.37 mA/cm2, VOC = 660 mV, FF = 82.78%) is obtained. Our simulation results also show that the n-i-p configuration of the Sb2Se3-based solar cell is more stable.

Electronic Properties of the Boron–Oxygen Defect Precursor of the Light-Induced Degradation in Silicon

In this work, we study the electronic properties of the boron–oxygen precursor defect responsible for light-induced degradation in crystalline silicon via deep-level transient spectroscopy. Even though this degradation has been known for many decades, and has resulted in severe silicon solar cell degradation, its root cause is poorly understood. The detection of a deep defect correlated to BO degradation has only been reported recently using deep-level transient spectroscopy. The resulting trap has been labeled as H390. In this work, we confirm the existence of this trap and report on the observation of a second defect (H400), which appears to be similarly associated with the BO light-induced degradation. To the best of our knowledge, this level has not been previously reported and could result from a second latent form of the BO light-induced degradation defect, a topic that has been largely debated in the literature. The concentration of both levels increases following dark annealing and decreases following minority carrier injection. The two levels disappear during BO activation and appear during BO deactivation, confirming a link between the observed levels and the latent state of the BO defect. Furthermore, consistent with previous studies, the two traps are metastable and change configurations after hole capture. Finally, we determine the minority carrier capture cross-section of the active BO defect by comparing the latent defect concentration with the minority carrier lifetime.

An all optical approach for comprehensive in-operando analysis of radiative and nonradiative recombination processes in GaAs double heterostructures

We demonstrate an all optical approach that can surprisingly offer the possibility of yielding much more information than one would expect, pertinent to the carrier recombination dynamics via both radiative and nonradiative processes when only one dominant deep defect level is present in a semiconductor material. By applying a band-defect state coupling model that explicitly treats the inter-band radiative recombination and Shockley–Read–Hall (SRH) recombination via the deep defect states on an equal footing for any defect center occupation fraction, and analyzing photoluminescence (PL) as a function of excitation density over a wide range of the excitation density (e.g., 5–6 orders in magnitude), in conjunction with Raman measurements of the LO-phonon plasmon (LOPP) coupled mode, nearly all of the key parameters relevant to the recombination processes can be obtained. They include internal quantum efficiency (IQE), minority and majority carrier density, inter-band radiative recombination rate (Wr), minority carrier nonradiative recombination rate (Wnr), defect center occupation fraction (f), defect center density (Nt), and minority and majority carrier capture cross-sections (σt and σtM). While some of this information is thought to be obtainable optically, such as IQE and the Wr/Wnr ratio, most of the other parameters are generally considered to be attainable only through electrical techniques, such as current-voltage (I-V) characteristics and deep level transient spectroscopy (DLTS). Following a procedure developed herein, this approach has been successfully applied to three GaAs double-heterostructures that exhibit two distinctly different nonradiative recombination characteristics. The method greatly enhances the usefulness of the simple PL technique to an unprecedented level, facilitating comprehensive material and device characterization without the need for any device processing.

Effect of Doping, Photodoping, and Bandgap Variation on the Performance of Perovskite Solar Cells

AbstractMost traditional semiconductor materials are based on the control of doping densities to create junctions and thereby functional and efficient electronic and optoelectronic devices. The technology development for halide perovskites had initially only rarely made use of the concept of electronic doping of the perovskite layer and instead employed a variety of different contact materials to create functionality. Only recently, intentional or unintentional doping of the perovskite layer is more frequently invoked as an important factor explaining differences in photovoltaic or optoelectronic performance in certain devices. Here, numerical simulations are used to study the influence of doping and photodoping on photoluminescence quantum yield and other device relevant metrics. It is found that doping can improve the photoluminescence quantum yield by making radiative recombination faster. This effect can benefit, or harm, photovoltaic performance given that the improvement of photoluminescence quantum efficiency and open‐circuit voltage is accompanied by a reduction of the diffusion length. This reduction will eventually lead to inefficient carrier collection at high doping densities. The photovoltaic performance may improve at an optimum doping density which depends on a range of factors such as the mobilities of the different layers and the ratio of the charge carrier capture cross sections.

TCAD simulation for capture/emission of carriers by traps in SiN: trap-assisted tunneling model extended for capture of carriers injected via Fowler–Nordheim tunneling

We propose the novel trap-assisted tunneling (TAT) model that incorporates the ability to calculate dissipation of the kinetic energy of carriers propagating in the conduction or valence band. The proposed model allows us to evaluate capture efficiency (or the capture cross section) of carriers injected into the SiN charge trap layer via Fowler–Nordheim tunneling. By applying our TAT model to large planar metal-oxide-nitride-oxide-semiconductor (MONOS) capacitors, experimental data showing that electron capture efficiency depends on the tunnel oxide thickness are physically interpreted. Furthermore, three-dimensional technology computer-aided design (TCAD) simulation using SiN trap parameters roughly extracted from planar MONOS data shows that the incremental step pulse programming characteristics calculated for the charge trap memory (CTM) prototype device are comparable with measured data. We have found that additional time to calculate SiN trap charges is less than only 5% of all remaining calculation time.

DASP: Defect and Dopant ab-initio Simulation Package

Abstract In order to perform automated calculations of defect and dopant properties in semiconductors and insulators, we developed a software package, the Defect and Dopant ab-initio Simulation Package (DASP), which is composed of four modules for calculating: (i) elemental chemical potentials, (ii) defect (dopant) formation energies and charge-state transition levels, (iii) defect and carrier densities and (iv) carrier dynamics properties of high-density defects. DASP uses the materials genome database for quick determination of competing secondary phases when calculating the elemental chemical potential that stabilizes compound semiconductors. DASP calls the ab-initio software to perform the total energy, structural relaxation and electronic structure calculations of the defect supercells with different charge states, based on which the defect formation energies and charge-state transition levels are calculated. Then DASP can calculate the equilibrium densities of defects and electron and hole carriers as well as the Fermi level in semiconductors under different chemical potential conditions and growth/working temperature. For high-density defects, DASP can calculate the carrier dynamics properties such as the photoluminescence (PL) spectrum and carrier capture cross sections which can interpret the deep level transient spectroscopy (DLTS). Here we will show three application examples of DASP in studying the undoped GaN, C-doped GaN and quasi-one-dimensional SbSeI.

Modeling diffusion length damage coefficient in GaAs and InGaP solar cells under electron irradiation

A method is proposed for calculating the diffusion length damage coefficient for minority carriers (KL) in GaAs and InGaP solar cells under electron irradiation using the Shockley–Read–Hall (SRH) model for defect-assisted recombination. In the SRH model, the damage coefficient KL is proportional to the product kσc, where k is the defect introduction rate under particle radiation and σc is the minority carrier capture cross section of the said defects. The introduction rate k is evaluated using the atomic theory for displacement under electron radiation, and the calculation for σc is adapted from Henry and Lang’s high-temperature multiphonon emission formulation. A linear scaling relationship is observed between k,KL and nonionizing energy loss—validated by bibliographic data in the radiation energy range E≈0.7–12 MeV. Our model reproduces the increasing trend in KL with doping, as observed in the literature, while also capturing the anisotropy between the p-type and n-type materials, with the p-type exhibiting greater radiation resistance than its n-type counterpart. The calculated KL is fed into the physical model for solar cell operation to obtain the post-irradiated Isc,Voc,Pmax at a given fluence Φ. The degradation of the electrical quantities is consistent with the measurements recorded in the literature. The findings show that InGaP is more radiation resistant than GaAs. It is demonstrated that calculating k not only aids in determining the degradation of solar cell parameters from first principles, but also in obtaining the empirical function for degradation: a−blog(1+ckΦ), used in fitting the experimental measurements. The limitations and potential scope of improvements in the model are also discussed.

Decay of excess carriers in a two-defect model semiconductor: A time-resolved photoluminescence study

The study of charge carrier decay dynamics in semiconductors plays an important role in determining various device properties, for example, the bulk minority carrier lifetime and the potential drop at interfaces. Time-resolved photoluminescence spectroscopy is an efficient technique to extract carrier decay time constants, with the simplest case being that of a mono-exponential decay controlled by a single type of recombination center. However, many modern materials often display multi-exponential decay behavior influenced by a broad distribution of defects. Utilizing CuIn1-xGaxSe2 as a reference system, we present a comprehensive and systematic theoretical study of the decay kinetics in a non-interacting two-defect-level system by using both the classical analytical approach developed by Hornbeck and Haynes and a homogeneous kinetic rate equation model solved numerically. We show how the trapping level's carrier capture cross-section symmetry factor and the initial injection level controls the parameter range for the agreement between these two approaches, analyzing the validity of multi-exponential fits for extracting the carrier lifetime. Further, we analytically and numerically demonstrate that information on the carrier recombination lifetime is contained in the fast time constant, whereas the agreement of the subsequent slow time constant with the analytical model depends on the energetic position of the defect level within the bandgap.

Optical activation and detection of charge transport between individual colour centres in diamond

Charge control of color centers in semiconductors promises opportunities for novel forms of sensing and quantum information processing. Here, we articulate confocal fluorescence microscopy and magnetic resonance protocols to induce and probe charge transport between discrete sets of engineered nitrogen-vacancy (NV) centers in diamond, down to the level of individual defects. In our experiments, a "source" NV undergoes optically-driven cycles of ionization and recombination to produce a stream of photo-generated carriers, one of which we subsequently capture via a "target" NV several micrometers away. We use a spin-to-charge conversion scheme to encode the spin state of the source color center into the charge state of the target, in the process allowing us to set an upper bound to carrier injection from other background defects. We attribute our observations to the action of unscreened Coulomb potentials producing giant carrier capture cross-sections, orders of magnitude greater than those typically attained in ensemble measurements. Besides their fundamental interest, these results open intriguing prospects in the use of free carriers as a quantum bus to mediate effective interactions between paramagnetic defects in a solid-state chip.

First-principles identification of deep energy levels of sulfur impurities in silicon and their carrier capture cross sections

Studies of the deep energy levels and nonradiative carrier capture induced by sulfur doping in silicon were initiated 60 years ago; however, the defect configurations, their deep energy levels, and the carrier capture cross sections are still not well understood. In this study, we focus on SSi substitution, and perform a first-principles study of its defect configurations and the deep energy levels using hybrid exchange-correlation functional. We discover a new distortive configuration for SSi + besides the previously obtained structure with higher symmetry. For both SSi + configurations, the deep transition levels (0/+) and (+/2+) are determined as 0.35 eV and 0.68 eV below the conduction band minimum, respectively. As a benchmark calculation, the hole-capture cross sections for neutral and +1 charged states are obtained based on the distortive structure. The cross section for SSi + agrees with the experiment, demonstrating the multi-phonon process for SSi + capturing a hole, whereas the cross section of SSi 0 is significantly lower than the experimental data because hole capture by SSi 0 is an Auger-type process. Our calculations provide a benchmark for the evaluation of the cross section of carrier capture in semiconductors using multi-phonon nonradiative recombination theory.

Deep level transient spectroscopy characterization without the Arrhenius plot.

Defect characterization by deep level transient spectroscopy (DLTS) requires the extraction of two key quantities of the carrier emission rate from the defects-activation energy (Ea) and pre-exponential factor (ν0)-the latter is related to the carrier capture cross section. This task, ubiquitous to thermally activated processes besides defect-carrier interaction, is traditionally accomplished by constructing an Arrhenius plot with DLTS peak locations and fitting it with a line. We present a transformation method based on the Arrhenius equation that extracts Ea and ν0without constructing or line-fitting the Arrhenius plot and bypasses peak identification. This method is developed on the basis of the fundamental temperature-rate duality relationship and extracts Ea and ν0 by matching the curvatures the Arrhenius-transformed spectra of the iso-thermal and iso-rate DLTS scans in the 2D temperature-rate plane. The extraction can be conducted with data in a small temperature range and is, therefore, capable of unambiguously resolving Ea and ν0 at any temperature point and their temperature dependence, if any.

First-principles study on non-radiative carrier captures of point defects associated with proton generation in silica

The non-radiative carrier captures of point defects associated with proton generation in both crystalline (α-quartz) and amorphous silica (a-SiO2) have been investigated by using first-principles calculations based on the density functional theory. Major point defects related to proton generation are considered, including the dimer and puckered configuration of oxygen vacancy, doubly hydrogenated oxygen vacancy, and hydroxyl E′ center. The carrier capture cross sections of the defects are calculated in terms of a one-dimensional static coupling method. The neutral dimer and doubly hydrogenated oxygen vacancies show a large hole capture cross section, and the positively charged puckered oxygen vacancy and the hydroxyl E′ center show a large electron capture cross section. These results further support that dissociation of molecular hydrogen at a positively charged dimer oxygen vacancy and that of a positively charged doubly hydrogenated oxygen vacancy are the main reactions in silica to generate protons that play a key role in ionization damage of silicon devices.

Carrier recombination and diffusion in high-purity diamond after electron irradiation and annealing

Carrier-transport mechanisms are studied in high-purity diamond irradiated with 6 MeV electrons in the dose range of 1012–1016 cm−2 and annealed at different temperatures up to 1450 °C. Lifetimes and diffusion coefficients are extracted using two pump–probe techniques based on free-carrier absorption and transient-grating principles and then correlated with the corresponding defect evolution from spectroscopic measurements. The neutral monovacancy is revealed as the main carrier recombination center in the as-irradiated diamond, providing bipolar carrier lifetimes of a few nanoseconds at the highest irradiation dose. Carrier-capture cross sections are reduced during annealing as vacancies aggregate into divacancies at ≤1000 °C and extended vacancy clusters at 1450 °C.