Time-resolved Photoluminescence Experiments Research Articles

Efficient Energy Transfer from Quantum Dots to Closely-Bound Dye Molecules without Spectral Overlap.

Quantum dots (QDs) are semiconductor nanocrystals whose optical properties can be tuned by altering their size. By combining QDs with dyes we can make hybrid QD-dye systems exhibiting energy transfer (ET) between QDs and dyes, which is important in sensing and lighting applications. In conventional QDs that need a shell to passivate surface defects, ET usually proceeds through Förster resonance energy transfer (FRET) that requires significant spectral overlap between QD emission and dye absorbance, as well as large oscillator strengths of those transitions. This considerably limits the choice of dyes. In contrast, perovskite QDs do not require passivating shells for bright emission, which makes ET mechanisms beyond FRET accessible. This work explores the design of a CsPbBr3 QD-dye system to achieve efficient ET from CsPbBr3 QDs to dyes with dimethyl iminium binding groups where the close binding of dyes surface facilitates spatial wavefunction overlap. Using steady-state and time-resolved photoluminescence experiments, we demonstrate that efficient ET from CsPbBr3 to dyes with minimal spectral overlap proceeds via the Dexter exchange-type mechanism, which overcomes the conventional restriction of spectral overlap that severely limits the tunability of these systems. This approach opens new avenues for QD-molecule hybrids for a wide range of applications.

Tetrazole and Oxadiazole Derivatives as Thermally Activated Delayed Fluorescence Emitters.

Organic light-emitting diodes (OLEDs) are promising lighting solutions for sustainability and energy efficiency. Incorporating thermally activated delayed fluorescence (TADF) molecules enables OLEDs to achieve internal quantum efficiency (IQE), in principle, up to 100 %; therefore, new classes of promising TADF emitters and modifications of existing ones are sought after. This study explores the TADF emission properties of six designed TADF emitters, examining their photophysical responses using experimental and theoretical methods. The design strategy involves creating six distinct types of a donor-acceptor (D-A) system, where tert-butylcarbazoles are used as donors, while the acceptor component incorporates three different functional groups: nitrile, tetrazole and oxadiazole, with varying electron-withdrawing character. Additionally, the donor-acceptor distance is adjusted using a phenylene spacer, and its influence on TADF functionality is examined. The clear dependency of an additional spacer, inhibiting TADF, could be revealed. Emitters with a direct donor-acceptor connection are demonstrated to exhibit TADF moderate emissive behavior. The analysis emphasizes the impact of charge transfer, singlet-triplet energy gaps (ΔEST), and other microscopic parameters on photophysical rates, permitting TADF. Among the emitters, TCz-CN shows optimal performance as a blue-green emitter with an 88 % photoluminescence quantum yield (PLQY) and fast rate of reversible intersystem crossing of 2×106 s-1 and 1×107 s-1, obtained from time-resolved photoluminescence (TRPL) experiment in PMMA matrix and quantum mechanical calculations, respectively. This comprehensive exploration identifies molecular bases of superior TADF emitters and provides insights for future designs, advancing the optimization of TADF properties in OLEDs.

Linker Engineering toward Tunable Emission Behavior of Porous Interpenetrated Zr-Organic Frameworks.

Conjugated molecules with donor-acceptor-donor (D-A-D) moieties have garnered significant attention for their ability to form luminescent metal-organic frameworks (LMOFs). D-A-D molecules feature tunable bandgaps, which can be varied systematically to control the fluorescence wavelength of LMOFs. In this study, we prepared and characterized the fluorescence properties of two porous interpenetrated Zr-organic frameworks (PIZOFs) constructed using 4,4'-(benzo[c][1,2,5]selenadiazole-4,7-diylbis(ethyne-2,1-diyl))dibenzoic acid (L-Se) or 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))dibenzoic acid (L-S) as linkers. The corresponding MOFs are denoted as PIZOF-Se and PIZOF-S, respectively. Through our investigation, we explored the correlation between the structure of the frameworks and their respective optical properties. Our findings revealed that there are distinct differences in the fluorescence properties of the two PIZOFs. Specifically, the fluorescence of PIZOF-S is red-shifted from that characteristic of the corresponding linker, L-S. By contrast, the fluorescence of PIZOF-Se is substantially blue-shifted from that of linker L-Se. The emission of mixed-linker MOFs is explored by combining L-S or L-Se with structurally analogous, but nonfluorescent linker, 4,4'-((perfluoro-1,4-phenylene)bis(ethyne-2,1-diyl))dibenzoic acid (L-F). Based on steady-state and time-resolved photoluminescence experiments, as well as confocal fluorescence microscopy combined with fluorescence lifetime imaging (FILM), we demonstrated that linker engineering is an effective method to tune the emission behavior of LMOFs.

Extending Infrared Emission via Energy Transfer in a CsPbI3-Cyanine Dye Hybrid.

Directing energy flow in light harvesting assemblies of nanocrystal-chromophore hybrid systems requires a better understanding of factors that dictate excited-state processes. In this study, we explore excited-state interactions within the CsPbI3-cyanine dye (IR125) hybrid assembly through a comprehensive set of steady-state and time-resolved absorption and photoluminescence (PL) experiments. Our photoluminescence investigations reveal the quenching of CsPbI3 emission alongside the simultaneous enhancement of IR125 fluorescence, providing evidence for a singlet energy transfer. The evaluation of both photoluminescence (PL) quenching and PL decay measurements yield ∼94% energy transfer efficiency for the CsPbI3-IR125 hybrid assembly. Transient absorption spectroscopy further unveils that this singlet energy transfer process operates on an ultrafast time scale, occurring within 400 ps with a rate constant of energy transfer of 1.4 × 1010 s-1. Our findings highlight the potential of the CsPbI3-IR125 hybrid assembly to extend the emission of halide perovskites into the infrared region, paving the way for light energy harvesting and display applications.

APTES functionalization in SBA-15: the effect on SO2 capture and detection applications.

The development of adsorbents for air pollutant remediation and effective monitoring is of interest. Then, the effect of the APTES functionalization ratio on the impact of the adsorption and detection of SO2 molecules was evaluated. The higher APTES functionalization material (SBA-15_6.1APTES) shows a high uptake of 1.15 mmol g-1 at 0.001 bar and 298 K. Fluorescence, time-resolved photoluminescence, and quantum yield experiments revealed a turn-on effect specifically for SO2 molecules, indicating high selectivity, suggesting host-to-guest energy transfer. Attractively, XPS measurement provided an understanding of the mechanism, suggesting hydrogen bonding and dipole-dipole interactions as the main interactions between SO2 molecules and SBA-15_6.1APTES. DFT calculations were performed to confirm these interactions. Furthermore, this study highlights the application of SBA-15 materials with different amino modifications for SO2 treatment and provides insight into the interaction mechanism using experimental techniques.

Excitonic Quantum Coherence in Light Emission from CsPbBr3 Metal-Halide Perovskite Nanocrystals.

The decay of excited states via radiative and nonradiative paths is well understood in molecules and bulk semiconductors but less so in nanocrystals. Here, we perform time-resolved photoluminescence (t-PL) experiments on CsPbBr3 metal-halide perovskite nanocrystals, with a time resolution of 3 ps, sufficient to observe the decay of both excitons and biexcitons as a function of temperature. The striking result is that the radiative rate constant of the single exciton increases at low temperatures with an exponential functional form, suggesting quantum coherent effects with dephasing at high temperatures. The opposing directions of the radiative and nonradiative decay rate constants enable enhanced brightening of PL from excitons to biexcitons due to quantum effects, promoting a faster approach to the quantum theoretical limits of light emission. Ab initio quantum dynamics simulations reproduce the experimental observations of radiation controlled by quantum spatial coherence enhanced at low temperatures.

Enhancing Multiexcitonic Emission in Metal-Halide Perovskites by Quantum Confinement.

Semiconductor metal halide perovskite nanocrystals have been under intense investigation for their promise in a variety of optoelectronic applications, which arises from their remarkable properties of defect tolerance and efficient light emission. Recently, quantum dot versions of perovskite nanocrystals have been available, enabling investigation of how quantum size effects control optical function and performance in these quantum dots (QD), past their well-known covalent II-VI analogues. We perform time-resolved photoluminescence (t-PL) experiments on CsPbBr3 perovskite nanocrystals spanning in diameter from 5.8 nm strongly confined quantum dots to 18 nm weakly confined quantum dots. Experiments are performed with sufficient time resolution of 3 ps to observe the interaction energies and recombination kinetics from excitons to multiexcitons. Comparing the same sized QD reveals that perovskite QD have a larger radiative rate constant for emission from X than CdSe QD due to a larger oscillator strength. The multiexciton (MX) regime reveals that perovskite QD emit brightly and with more focused bandwidth than equivalent sized CdSe QD enabling more spectrally pure brightness. The MX kinetics reveals that the perovskite QD maintain efficient radiative decay, effectively competing with Auger recombination. These experiments reveal that the strongly confined QD of perovskites can be efficient multiexcitonic emitters, such as in high brightness light emitting diodes, especially in the blue.

Temperature dependent temporal coherence of metallic-nanoparticle-induced single-photon emitters in a WSe2 monolayer

In recent years, much research has been undertaken to investigate the suitability of two-dimensional materials to act as single-photon sources with high optical and quantum optical quality. Amongst them, transition-metal dichalcogenides, especially WSe2, have been one of the subjects of intensive studies. Yet, their single-photon purity and photon indistinguishability remain the most significant challenges to compete with mature semiconducting systems such as self-assembled InGaAs quantum dots. In this work, we explore the emission properties of quantum emitters in a WSe2 monolayer which are induced by metallic nanoparticles. Under quasi-resonant pulsed excitation, we verify clean single-photon emission with a g (2)(0) = 0.036 ± 0.004. Furthermore, we determine the temperature dependent coherence time via Michelson interferometry, where a value of (13.5 ± 1.0) ps is extracted for the zero-phonon line at 4 K, which reduces to (9 ± 2) ps at 8 K. Associated time-resolved photoluminescence experiments reveal a decrease of the decay time from (2.4 ± 0.1) ns to (0.42 ± 0.05) ns. This change in decay time is explained by a model which considers a Förster-type resonant energy transfer process which yields a strong temperature induced energy loss from the single-photon emitters to the nearby Ag nanoparticle.

Fabricated ZnO@ZnIn2S4 S-scheme heterojunction photocatalyst for enhanced electron-transfer and CO2 reduction

Step-scheme (S-scheme) heterojunctions can efficiently promote the separation of photogenerated carriers while maintaining the strong oxidation/reduction ability of photocatalysts; thus, research attention on S-scheme heterojunctions is increasing year by year. In this study, the S-scheme ZnO@ZnIn2S4 (ZnO@ZIS) heterojunction was prepared successfully. Then, electron spin resonance (ESR) characterization was applied to prove the successful construction of the S-scheme heterojunction. Photoluminescence (PL), time-resolved photoluminescence (TRPL), and photoelectrochemical experiments have demonstrated efficient interfacial charge transport in ZnO@ZIS. Finally, the mechanism of CO2 activation and electron transport was investigated by in situ Fourier transform infrared spectroscopy (FT-IR) and discrete Fourier transform (DFT) calculation analysis. The 40-ZnO@ZIS composite showed the best activity under light, and its CO and CH4 yields reached 39.76 and 3.92 μmol∙g−1∙h−1, respectively. This study provides a solution for optimizing the photocatalytic reduction activity of semiconductor photocatalysts by constructing S-scheme heterojunction materials to improve the CO2 reduction capacity.

Spectroelectrochemistry of CdSe/CdxZn1-xS Nanoplatelets.

We report an unexpected enhancement of photoluminescence (PL) in CdSe-based core/shell nanoplatelets (NPLs) upon electrochemical hole injection. Moderate hole doping densities induce an enhancement of more than 50% in PL intensity. This is accompanied by a narrowing and blue-shift of the PL spectrum. Simultaneous, time-resolved PL experiments reveal a slower luminescence decay. Such hole-induced PL brightening in NPLs is in stark contrast to the usual observation of PL quenching of CdSe-based quantum dots following hole injection. We propose that hole injection removes surface traps responsible for the formation of negative trions, thereby blocking nonradiative Auger processes. Continuous photoexcitation causes the enhanced PL intensity to decrease back to its initial level, indicating that photocharging is a key step leading to loss of PL luminescence during normal aging. Modulating the potential can be used to reversibly enhance or quench the PL, which enables electro-optical switching.

Detection of SO2 using a chemically stable Ni(II)-MOF.

The MOF-type Ni2(dobpdc) shows a high chemical stability towards SO2, high capacity for SO2 capture at low pressure (4.3 mmol g-1 at 298 K and up to 0.05 bar), and exceptional cycling performance. Fluorescence experiments demonstrated the SO2 detection properties of Ni2(dobpdc) with a remarkable SO2 detection selectivity. Finally, time-resolved photoluminescence experiments provided a plausible mechanism of SO2 detection by this Ni(II)-based MOF material.

Evaluating Recombination Mechanisms in RbF Treated Cu(In${}_\mathrm{x}$Ga$_\mathrm{1-x}$)Se$_{2}$ Solar Cells

Rubidium fluoride (RbF) postdeposition treatment (PDT) has been shown to improve the performance of Cu(In <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${}_\mathrm{x}$</tex-math></inline-formula> Ga <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_\mathrm{1-x}$</tex-math></inline-formula> )Se <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> (CIGS) photovoltaic devices. In this study, temperature-dependent current voltage (JVT) and time-resolved photoluminescence (TRPL) experiments were combined with modeling using the solar cell capacitance simulator (SCAPS) computer code to investigate the effect of the RbF PDT. Two devices, one as-deposited and one with RbF PDT, were deposited by a three stage coevaporation process. JVT measurements suggest the dominant recombination mechanism may be tunneling-enhanced recombination via bandtail states, but that defect states in the bandgap can also be important. RbF PDT is shown to decrease the characteristic energy of the bandtails. TRPL data show an increase in the minority carrier lifetime after RbF PDT, leading to an improved open-circuit voltage. SCAPS modeling indicates that the dominant recombination mechanism is dependent on the specific defect makeup of a device, suggesting that small changes in processing conditions can impact device behavior. This explains the observation that, for some devices, defect states in the gap dominate while others, as is the case here, appear to be dominated by bandtails.

Identity of the reversible hole traps in InP/ZnSe core/shell quantum dots.

Density functional theory calculations are combined with time-resolved photoluminescence experiments to identify the species responsible for the reversible trapping of holes following photoexcitation of InP/ZnSe/ZnS core/shell/shell quantum dots (QDs) having excess indium in the shell [P. Cavanaugh et al., J. Chem. Phys. 155, 244705 (2021)]. Several possible assignments are considered, and a substitutional indium adjacent to a zinc vacancy, In3+/VZn 2-, is found to be the most likely. This assignment is consistent with the observation that trapping occurs only when the QD has excess indium and is supported by experiments showing that the addition of zinc oleate or acetate decreases the extent of trapping, presumably by filling some of the vacancy traps. We also show that the addition of alkyl carboxylic acids causes increased trapping, presumably by the creation of additional zinc vacancies. The calculations show that either a single In2+ ion or an In2+-In3+ dimer is much too easily oxidized to form the reversible traps observed experimentally, while In3+ is far too difficult to oxidize. Additional experimental data on InP/ZnSe/ZnS QDs synthesized in the absence of chloride demonstrates that the reversible traps are not associated with Cl-. However, a zinc vacancy adjacent to a substitutional indium is calculated to have its highest occupied orbitals about 1eV above the top of the valence band of bulk ZnSe, in the appropriate energy range to act as reversible traps for quantum confined holes in the InP valence band. The associated orbitals are predominantly composed of p orbitals on the Se atoms adjacent to the Zn vacancy.

Resolving decay-time dependent photoluminescence induced by phonon-dressed excitons in ZnO

Time-resolved photoluminescence (PL) experiments on ZnO crystals have been conducted at room temperature to elucidate the origins of a near-band edge (NBE) emission. A temporal profile of the PL spectra exhibits a two-curve structure with different decaying rates and is reproduced reasonably by a biexponential function, indicating that there are at least two origins with different decay times in the NBE emission. By taking free exciton (FX)--longitudinal optical (LO) phonon interactions into account in the analysis of the PL spectra, the faster and slower decaying emissions are found to be associated with stronger and weaker FX-LO phonon coupling, respectively. We propose that the NBE emissions with different decay times are related to crystal imperfections; the fast-decaying emission originates from the region with a higher density of defects or impurities, while the slower one is from the regions with better crystallinity.

Pyrene-substituted cyclic triimidazole: An appealing and versatile luminescent scaffold for explosive detection

Two derivatives of cyclic triimidazole and pyrene, namely the blue emitting 3-(pyren-1-yl)triimidazo[1,2-a:1′,2′-c:1″,2″-e] [1,3,5]triazine, TTPyr, and the yellow-orange emitting 11-(pyren-1-yl)triimidazo[1,2-a:1′,2′-c:1″,2″-e][1,3,5]triazine-3,7-dicarbaldehyde, (CHO)2TTPyr, are here exploited for titration experiments with various nitroaromatic energetic hazardous materials and proposed as sensor species for the quantitative detection of explosives. The 565 nm fluorescence of (CHO)2TTPyr represents a valid alternative to the TTPyr 420 nm one for analytes absorbing in the blue region. (CHO)2TTPyr displays varying degrees of fluorescence quenching towards different nitroaromatics, among which picric acid (PA) detection has the highest sensitive response with a Stern-Volmer quenching constant value equal to 1.25 × 104 M−1 and a calculated detection limit of 0.63 ppm. From time resolved photoluminescence experiment, a static mechanism is recognized as responsible for the observed quenching. The hypothesis of a dark complex formation is supported through the isolation and characterization of a TTPyr/PA adduct with 2:1 stoichiometry.

Interdash Coupling within Dense Ensembles of Quantum Dashes: Comparison of InAs /( In , Al , Ga ) As / InP and InAs /( In , Al ) As

Lasers, light-emitting diodes, and other optoelectronic devices employing $\mathrm{In}\mathrm{As}$/$\mathrm{In}\mathrm{P}$ quantum dots (QDs) instead of quantum wells (QWs) as their active parts benefit from the quasi-zero-dimensional (0D) density of states while maintaining the emission at the communication-relevant range of $1.55\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$. However, for certain application purposes, the substitution of QWs with QDs is advantageous only if QDs can either be treated as isolated objects or exhibit quantum-mechanical coupling between deeply confined states. Here, we compare two material systems of $\mathrm{In}\mathrm{As}$/($\mathrm{In}$,$\mathrm{Al}$,$\mathrm{Ga}$)$\mathrm{As}$/$\mathrm{In}\mathrm{P}$ and $\mathrm{In}\mathrm{As}$/($\mathrm{In}$,$\mathrm{Al}$)$\mathrm{As}$/$\mathrm{In}\mathrm{P}$ elongated QDs (quantum dashes, QDashes) of comparable surface densities and interdash distances. We investigate the presence and type of coupling between QDashes, focusing on the direct tunnel coupling for both types of carriers manifested already at low temperature. In the time-resolved photoluminescence (PL) experiment, we observe a significant dispersion of the PL decay time for $\mathrm{In}\mathrm{As}$/($\mathrm{In}$,$\mathrm{Al}$,$\mathrm{Ga}$)$\mathrm{As}$ QDashes, resulting from the migration of carriers from high- to low-energy QDashes due to substantial tunnel coupling. In the case of $\mathrm{In}\mathrm{As}$/($\mathrm{In}$,$\mathrm{Al}$)$\mathrm{As}$ QDashes, the dispersionless time dependence points toward the absence of such coupling. We confirm this interpretation with multiband $\mathbit{k}\ensuremath{\cdot}\mathbit{p}$ calculations. We check that the proposed coupling scenario is possible and show its much higher probability for $\mathrm{In}\mathrm{As}$/($\mathrm{In}$,$\mathrm{Al}$,$\mathrm{Ga}$)$\mathrm{As}$ than for $\mathrm{In}\mathrm{As}$/($\mathrm{In}$,$\mathrm{Al}$)$\mathrm{As}$ QDashes. Finally, in temperature-dependent PL, we observe the redistribution of holes among QDashes via thermal excitation to wetting-layer states for both systems, constituting an additional interdash coupling channel at elevated temperatures. Our results indicate that the $\mathrm{In}\mathrm{As}$/($\mathrm{In}$,$\mathrm{Al}$)$\mathrm{As}$ QDash system is preferential for optoelectronic applications where QD isolation is highly sought after, whereas $\mathrm{In}\mathrm{As}$/($\mathrm{In}$,$\mathrm{Al}$,$\mathrm{Ga}$)$\mathrm{As}$ QDashes exhibit quantum-mechanical coupling between deeply confined states.

Defect-induced distinct exciton-exciton interactions in WS2 monolayers

The optoelectronic properties of atomically thin transition metal dichalcogenides (TMDs) are largely influenced by defect populations (DPs). In this work, we fabricate WS2 monolayers with different DPs by varying the fabrication methods and further reveal their distinct exciton-exciton interactions. Steady-state photoluminescence (PL) experiments show that the monolayer with the lowest DP shows optimal PL intensity at low excitation power; however, it is overtaken and significantly surpassed by monolayers with higher DPs at high excitation powers. Excitation-power-dependent experiments demonstrate that these monolayers exhibit distinct PL saturation behaviors with the threshold power differing by four orders of magnitude. Combined with in situ PL imaging and time-resolved PL experiments, we attribute such PL evolution discrepancies to the different DPs within these monolayers, which largely influence the exciton diffusion behavior and subsequently bring about distinct nonradiative exciton-exciton annihilations (EEAs). Valley polarization experiments are further employed to re-examine the DPs of these monolayers. This work reveals the distinct PL behaviors and underlying exciton dynamics in TMD monolayers with different DPs, which can largely facilitate the engineering of relevant high-performance devices for practical applications.

Carrier dynamics of AlGaAs/AlAs asymmetric double quantum wells with different barrier thickness

Optical properties and carrier dynamics of AlGaAs/AlAs asymmetric double quantum wells (ADQWs) with varied barrier thickness are studied by excitation-power-dependent photoluminescence (PL) and temperature-dependent time-resolved PL (TRPL) experiments. The origin of the transition energies derived from the time-integrated spectra is confirmed by theoretical calculation using the Schrödinger equation. The carrier kinetics and the temporal behavior of the emission in the narrow well (NW) and wide well (WW) are physically revealed with varying barrier thicknesses by the TRPL measurements. For a better understanding of the carrier transport mechanism, the electron tunneling times for the ADQWs are theoretically estimated based on a rate-equation model. The calculation indicates that the electron tunneling time decreases with increasing temperature, which may be induced by enhanced phonon-assisted scattering.

Carrier Diffusion in GaN : A Cathodoluminescence Study. II. Ambipolar versus Exciton Diffusion

We determine the diffusion length of excess carriers in $\mathrm{Ga}\mathrm{N}$ by spatially resolved cathodoluminescence spectroscopy utilizing a single quantum well as a carrier collector or carrier sink. Monochromatic intensity profiles across the quantum well are recorded for temperatures between 10 and 300 K. A classical diffusion model accounts for the profiles acquired between 120 and 300 K, while for temperatures lower than 120 K, a quantum capture process has to be taken into account in addition. Combining the diffusion length extracted from these profiles and the effective carrier lifetime measured by time-resolved photoluminescence experiments, we deduce the carrier diffusivity as a function of temperature. The experimental values are found to be close to theoretical ones for the ambipolar diffusivity of free carriers limited only by intrinsic phonon scattering. This agreement is shown to be fortuitous. The high diffusivity at low temperatures instead originates from an increasing participation of excitons in the diffusion process.

Voltage Loss Comparison in CdSe/CdTe Solar Cells and Polycrystalline CdSeTe Heterostructures

Cd(Se)Te solar cells have considerable headroom to increase voltage. Voltage losses occur due to incomplete absorption above bandgap <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E_g</i> and band tail absorption below <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E_g</i> ; such losses are quantified using radiative voltage. The largest voltage losses are attributed to nonradiative recombination, which is quantified via carrier lifetime and radiative efficiency. We compare radiative voltage, radiative efficiency, and carrier lifetime for Cu-doped CdSe/CdTe solar cells and for undoped polycrystalline CdSeTe heterostructures passivated with Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . Using external quantum efficiency spectrum and a CdSeTe absorption spectrum obtained from absolute photoluminescence (PL), we show that the radiative voltage is greater than 1.1 V. Time-resolved PL experiments and modeling show that a major part of voltage losses can be attributed to recombination in the absorber bulk. The front interface recombination makes a larger impact within the first few nanoseconds after pulsed excitation, and the comparison of time-gated and time-integrated PL can be used to assess relative contributions of front interface and bulk recombination rates.