Nonradiative Decay Channels Research Articles

Molecular Engineering through Control of Structural Deformation for Highly Efficient Ultralong Organic Phosphorescence.

It is an enormous challenge to achieve highly efficient organic room-temperature phosphorescence (RTP) with a long lifetime. We demonstrate that, by bridging the carbazole and halogenated phenyl ring with a methylene linker, RTP phosphors CzBX (X=Cl, Br) present high phosphorescence efficiency (ΦPh ). A ΦPh up to 38 % was obtained for CzBBr with a lifetime of 220 ms, which is much higher than that of compounds CzPX (X=Cl, Br) with a C-N bond as a linker (ΦPh <1 %). Single-crystal analysis and theoretical calculations revealed that, in the crystal phase, intermolecular π-Br interactions accelerate the intersystem crossing process, while tetrahedron-like structures induced by sp3 methylene linkers restrain the nonradiative decay channel, leading to the high phosphorescence efficiency in CzBBr. This research paves a new road toward highly efficient and long-lived RTP materials with potential applications in anti-counterfeiting or data encryption.

Molecular Engineering through Control of Structural Deformation for Highly Efficient Ultralong Organic Phosphorescence

AbstractIt is an enormous challenge to achieve highly efficient organic room‐temperature phosphorescence (RTP) with a long lifetime. We demonstrate that, by bridging the carbazole and halogenated phenyl ring with a methylene linker, RTP phosphors CzBX (X=Cl, Br) present high phosphorescence efficiency (ΦPh). A ΦPh up to 38 % was obtained for CzBBr with a lifetime of 220 ms, which is much higher than that of compounds CzPX (X=Cl, Br) with a C−N bond as a linker (ΦPh&lt;1 %). Single‐crystal analysis and theoretical calculations revealed that, in the crystal phase, intermolecular π‐Br interactions accelerate the intersystem crossing process, while tetrahedron‐like structures induced by sp3 methylene linkers restrain the nonradiative decay channel, leading to the high phosphorescence efficiency in CzBBr. This research paves a new road toward highly efficient and long‐lived RTP materials with potential applications in anti‐counterfeiting or data encryption.

Luminescence of a Two-Particle Complex from a Spherical Quantum Dot and Plasmon Nanoglobule in an External Magnetic Field

Based on a specially created theoretical model, frequency dependences of the luminescence intensity of the two-component “exciton-activated semiconductor quantum dot (QD)–plasmon nanoparticle (NP)” system in a constant magnetic field are calculated. In contrast to previous models, it goes beyond the scope of the approximation of dipole polarizability of a spherical NP. The induced NP dipole moment was calculated taking into account the inhomogeneous character of the field created by the QD containing an exciton. It is shown that, with a change in induction of the external magnetic field, one can observe transformation of exciton luminescence spectra of such system as a result of the exciton–plasmon interaction between cluster particles and magnetization of the NP electron plasma. The competition of radiative and nonradiative decay channels of the excited state of a two-particle complex is taken into account. It is shown that, in rate spectra of the nonradiative energy transfer from the QD to the NP, as well as of spontaneous emission of the nanocomplex, stripes of higher order multipole transitions are formed in addition to dipole stripes; they are split into doublet components in the magnetic field.

Inhibiting Radiative Transition-Mediated Multifunctional Polymeric Nanoplatforms for Highly Efficient Tumor Phototherapeutics.

It is highly desired to explore ideal phototherapeutic nanoplatforms, especially containing satisfactory phototherapeutic agents (PTAs), for potential cancer therapies. Herein, we proposed an effective strategy for designing a highly efficient PTA through inhibiting radiative transition (IRT). Specifically, we developed an ultralow radiative BODIPY derivative (TPA-IBDP) by simply conjugating two triphenylamine units to iodine-substituted BODIPY, which could simultaneously facilitate the nonradiative decay channels of singlet-to-triplet intersystem crossing and intramolecular charge transfer. In comparison to the normal BODIPY compound, TPA-IBDP exhibited an outstanding singlet oxygen yield (31.8-fold) and a higher photothermal conversion efficiency (PCE; over 3-fold), respectively, benefiting from the extended π-conjugated donor-to-accepter (D-A) structure and the heavy atom effect. For tumor phototherapy using TPA-IBDP, TPA-IBDP was conjugated with a H2O2-responsive amphiphilic copolymer POEGMA10-b-[PBMA5-co-(PS-N3)2] to construct a multifunctional phototherapeutic BODIPY-based nanoplatform (PB). PB produced abundant singlet oxygen (1O2) and heat along with negligible fluorescence emission under near-infrared laser irradiation. Additionally, PB could generate a GSH-depletion scavenger (quinone methide, QM) after reacting with the abundant intracellular H2O2 in tumor for the cooperative enhancement of IRT-mediated phototherapy. We envision that this highly efficient multifunctional phototherapeutic nanoplatform cooperated by GSH-depletion could be a valuable paradigm for tumor treatments.

Quantum Hamiltonian for the surface charge density on a ring torus and radiative decay of plasmons

Photon scattering and the ensuing excitation of surface plasmons in single rings, single composite rings, and many-ring systems was recently shown to provide dispersion and field distributions [K. V. Garapati et al., J. Phys. Commun. 2, 015031 (2018)] of potential for specific applications in particle and molecular trapping [R. Alaee et al., Appl. Phys. Lett. 109, 141102 (2016); M. Salhi et al., Phys. Rev. A 92, 033416 (2015)], in addition to metamaterials and sensing. Following photon or electron interactions with metallic nanorings, both radiative and nonradiative decay channels are important in the consideration of the nanoparticle as a photon or phonon source, and in related applications. Here, we quantize the electronic normal modes of the ring torus and obtain the radiative decay of plasmons. Due to a geometry-related complexity, we employ a perturbation approach to obtain analytical expressions for the radiative decay channel for a vacuum bounded single solid nanoring. In quantizing the fields, the frequency spectrum of the charge density normal modes of the nanoring is obtained and shown to agree with the exact quasistatic plasmon dispersion relations. Higher-order corrections beyond the presented zero- and first-order calculations may be obtained following the presented results. The results are of potential interest in quantum sensing such as entangling photons and plasmons, or plasmons and trapped molecules.

Excitonic Fine Structure in Emission of Linear Carbon Chains.

We studied monatomic linear carbon chains stabilized by gold nanoparticles attached to their ends and deposited on a solid substrate. We observe spectral features of straight chains containing from 8 to 24 atoms. Low-temperature PL spectra reveal characteristic triplet fine structures that repeat themselves for carbon chains of different lengths. The triplet is invariably composed of a sharp intense peak accompanied by two broader satellites situated 15 and 40 meV below the main peak. We interpret these resonances as an edge-state neutral exciton and positively and negatively charged trions, respectively. The time-resolved PL shows that the radiative lifetime of the observed quasiparticles is about 1 ns, and it increases with the increase of the length of the chain. At high temperatures a nonradiative exciton decay channel appears due to the thermal hopping of carriers between parallel carbon chains. Excitons in carbon chains possess large oscillator strengths and extremely low inhomogeneous broadenings.

Compositional Tuning of Carrier Dynamics in Cs2Na1-x Ag x BiCl6 Double-Perovskite Nanocrystals.

We devised a hot-injection synthesis to prepare colloidal double-perovskite Cs2NaBiCl6 nanocrystals (NCs). We also examined the effects of replacing Na+ with Ag+ cations by preparing and characterizing Cs2Na1–xAgxBiCl6 alloy NCs with x ranging from 0 to 1. Whereas Cs2NaBiCl6 NCs were not emissive, Cs2Na1–xAgxBiCl6 NCs featured a broad photoluminescence band at ∼690 nm, Stokes-shifted from the respective absorption by ≥1.5 eV. The emission efficiency was maximized for low Ag+ amounts, reaching ∼3% for the Cs2Na0.95Ag0.05BiCl6 composition. Density functional theory calculations coupled with spectroscopic investigations revealed that Cs2Na1–xAgxBiCl6 NCs are characterized by a complex photophysics stemming from the interplay of (i) radiative recombination via trapped excitons localized in spatially connected AgCl6–BiCl6 octahedra; (ii) surface traps, located on undercoordinated surface Bi centers, behaving as phonon-assisted nonradiative decay channels; and (iii) a thermal equilibrium between trapping and detrapping processes. These results offer insights into developing double-perovskite NCs with enhanced optoelectronic efficiency.

Trapping and Detrapping in Colloidal Perovskite Nanoplatelets: Elucidation and Prevention of Nonradiative Processes through Chemical Treatment.

Metal-halide perovskite nanocrystals show promise as the future active material in photovoltaics, lighting, and other optoelectronic applications. The appeal of these materials is largely due to the robustness of the optoelectronic properties to structural defects. The photoluminescence quantum yield (PLQY) of most types of perovskite nanocrystals is nevertheless below unity, evidencing the existence of nonradiative charge-carrier decay channels. In this work, we experimentally elucidate the nonradiative pathways in CsPbBr3 nanoplatelets, before and after chemical treatment with PbBr2 that improves the PLQY. A combination of picosecond streak camera and nanosecond time-correlated single-photon counting measurements is used to probe the excited-state dynamics over 6 orders of magnitude in time. We find that up to 40% of the nanoplatelets from a synthesis batch are entirely nonfluorescent and cannot be turned fluorescent through chemical treatment. The other nanoplatelets show fluorescence, but charge-carrier trapping leads to losses that are prevented by chemical treatment. Interestingly, even without chemical treatment, some losses due to trapping are mitigated because trapped carriers spontaneously detrap on nanosecond-to-microsecond timescales. Our analysis shows that multiple nonradiative pathways are active in perovskite nanoplatelets, which are affected differently by chemical treatment with PbBr2. More generally, our work highlights that in-depth studies using a combination of techniques are necessary to understand nonradiative pathways in fluorescent nanocrystals. Such understanding is essential to optimize synthesis and treatment procedures.

Influence of the Substrate on the Optical and Photo-electrochemical Properties of Monolayer MoS2.

Substrates influence the electrical and optical properties of monolayer (ML) MoS2 in field-effect transistors and photodetectors. Photoluminescence (PL) and Raman spectroscopy measurements have shown that conducting substrates can vary the doping concentration and influence exciton decay channels in ML-MoS2. Doping and exciton decay dynamics are expected to play a major role in the efficiency of light-driven chemical reactions, but it is unclear to what extent these factors contribute to the photo(electro)catalytic properties of ML-MoS2. Here, we report spatially resolved PL, Raman, and photo-electrochemical current measurements of 5-10 μm-wide ML-MoS2 triangles deposited on pairs of indium-doped tin oxide (ITO) electrodes that are separated by a narrow insulating quartz channel [i.e., an ITO interdigitated array (IDA) electrode]. Optical microscopy images and atomic force microscopy measurements revealed that the ML-MoS2 triangles lie conformally on the quartz and ITO substrates. The PL spectrum of MoS2 shifts and decreases in intensity in the ITO region, which can be attributed to differences in nonradiative and radiative exciton decay channels. Raman spectra showed no significant peak shifts on the two substrates that would have indicated a substrate-induced doping effect. We spatially resolved the photo-electrochemical current because of hole-induced iodide oxidation and observed that ML-MoS2 produces lower photocurrents in the quartz region than in the ITO region. The correlated PL, Raman, and photocurrent mapping data show that the MoS2/quartz interface diminishes fast nonradiative exciton decay pathways but the photocurrent response in the quartz region is likely limited by inefficient in-plane carrier transport to the ITO electrode because of carrier recombination with S vacancies in MoS2 or charged impurities in the quartz substrate. Nonetheless, the experimental methodology presented herein provides a framework to evaluate substrate engineering strategies to tune the (photo)electrocatalytic properties of two-dimensional materials.

Excited State Dynamics of 8-Vinyldeoxyguanosine In Aqueous Solution Studied by Time-Resolved Fluorescence Spectroscopy and Quantum Mechanical Calculations.

The fluorescent base guanine analog, 8-vinyl-deoxyguanosine (8vdG), is studied in solution using a combination of optical spectroscopies, notably femtosecond fluorescence upconversion and quantum chemical calculations, based on time-dependent density functional theory (TD-DFT) and including solvent effect by using a mixed discrete-continuum model. In all investigated solvents, the fluorescence is very long lived (3–4 ns), emanating from a stable excited state minimum with pronounced intramolecular charge-transfer character. The main non-radiative decay channel features a sizeable energy barrier and it is affected by the polarity and the H-bonding properties of the solvent. Calculations provide a picture of dynamical solvation effects fully consistent with the experimental results and show that the photophysical properties of 8vdG are modulated by the orientation of the vinyl group with respect to the purine ring, which in turn depends on the solvent. These findings may have importance for the understanding of the fluorescence properties of 8vdG when incorporated in a DNA helix.

Люминесценция двухчастичного комплекса из сферической квантовой точки и плазмонной наноглобулы во внешнем магнитном поле

On the basis of a specially created theoretical model, calculations of the frequency dependences of the glow intensity of the two-component exciton-activated semiconductor quantum dot (QD) - plasmon nanoparticle (NP) system in a constant magnetic field were made. In contrast to the previous models, we went beyond the approximation of the dipole polarizability of a spherical nanoparticle. When calculating the induced dipole moment of the NP, the inhomogeneous nature of the field created by the exciton-containing QD was taken into account. It is shown that with a change in the induction of the external magnetic field, the transformation of the exciton luminescence spectra of such a system is observed as a result of the exciton-plasmon interaction between the cluster particles and the magnetization of the NP electron plasma. The competition of radiation and non-radiative decay channels of the excited state of a two-particle complex is accounted for. It is shown that in the spectra of the rate of non-radiative energy transfer from QD to NP, as well as spontaneous emission of the nanocomplex, in addition to dipole bands, bands of multipole transitions of higher orders are formed, splitting into doublet components in the magnetic field.

Manipulating Nonradiative Decay Channel by Intermolecular Charge Transfer for Exceptionally Improved Photothermal Conversion.

In-depth studies of nonradiative (NR) decay, seeking to maximize NR decay rate or manipulate other NR decay channels, are of greatest significance for improving the photothermal conversion efficiency (η) of organic materials for phototheranostics; however, to date, relevant work remains scarce. Here, we present an insightful study of NR decay in BODIPY (BDP) dye, in an aggregated state, i.e., in BDP nanoparticles (BDP NPs), which show an efficient additional NR decay channel from the aggregation-stabilized intermolecular charge transfer (CT) state, resulting in exceptionally high η (61%) for highly efficient phototheranostics in vivo. BDP NPs exhibit two ultrafast NR decay channels with ultrashort lifetimes of 1.7 and 50 ps, which is in stark contrast to the only S1 → S0 NR channel with a long lifetime of 373 ps in the isolated BDP dye. More importantly, the ultrafast NR channel (1.7 ps) in BDP NPs depletes a substantial portion of the excited-state population (71%), which accounts for its much better photothermal effect as compared with the isolated BDP dye. Finally, BDP NPs display a highly efficient photoacoustic imaging (PAI) guided photothermal therapy (PTT) of tumors in live mice. This study presents a deeper fundamental understanding of NR decay in organic materials, setting a valuable guideline that may be widely applicable to similar molecular structure to develop more advanced organic materials not only for photothermal-related applications.

Following excited states in molecular systems using density-based indexes: A dual emissive system as a test case

Dual emission from single molecular species is a particularly appealing phenomenon to test the efficiency of theoretical approaches for the description of a complex excited state scenario.Recently, the Phen-PENMe2 molecule (Phen-PENMe2 = 5-(4-dimethylaminophenylenylethylyn)-1,10-phenanthroline) has been experimentally characterized and its dual emission has been ascribed to the presence of two emissive states of different electronic nature and corresponding to two structurally different species. Nonetheless, the full mechanism ruling the structural interconversion leading to dual emission has not yet been disclosed.To this end, in this paper the dual emissive behavior of Phen-PENMe2 has been unveiled by a combined use of time dependent density functional theory (TD-DFT) and density-based indexes (DCT and Π) allowing identifying the radiative and non-radiative decay pathways at work in this system. In particular, the possible presence of an anti-Kasha emission mechanism as well as the presence of several non-radiative decay channels allowing enhancing either of the two emissions has been proven.More generally, the results obtained in the present study highlight how this simple and inexpensive computational approach may be of help and general interest for the rational design of new dual emissive systems.

Tunable Twisting Motion of Organic Linkers via Concentration and Hydrogen-Bond Formation

Benzothiadiazole dibenzoic acid (BTDB) derivative is a well-known organic linker in various metal–organic framework structures as well as a fluorescent probe in biological systems. Here, we demonstrate that the radiative and nonradiative decay channels of BTDB can be interplayed and precisely controlled through concentration and hydrogen-bond interactions as directly evidenced experimentally and theoretically. This leads to excited-state structural changes that significantly suppress the torsional motion around the benzothiadiazole moiety, leading to an enormous increase in the emission quantum yields from ∼1 to 70%. These changes are associated with the existence of two equilibria, where dimers and small oligomers form in dimethylformamide (DMF), with high formation constants of 18 000 M–1 and 1.2 × 1013 M–3, respectively. These evolving species, i.e., the dimers and oligomers, are formed via hydrogen bonds between carboxylic acid groups present at the far edge of the rodlike BTDB molecules. The estimated repeating number for this small-oligomer formation via bonded monomers is eight in DMF, as shown by emission spectra analysis. With deprotonation as a control experiment, these associated species can easily collapse with the initial monomer species, confirming the role of the hydrogen-bond formation in the observed phenomena. Theoretical studies and NMR experiments not only confirm the existence of the dimers, but also demonstrate the important role of the hydrogen bonds in the excited-state dynamics. These new findings provide a better understanding of the photophysical behaviors of organic linkers used in a wide range of chemical and biological applications.

Theoretical Rationalization of the Dual Photophysical Behavior of C60+

Interest in fullerenes has been renewed recently in astrophysics as a consequence of their detection in circumstellar environments. In particular, C60+ was detected in the diffuse interstellar medium and its presence has been related to some diffuse interstellar bands (DIBs) whose origin was previously unknown. A single recent laboratory experiment ( J. Phys. Chem. A 2017, 121, 7356-7361) shows that upon laser excitation at 785 nm, C60+ in neon matrixes exhibits a radiative decay at 965 nm, while UV photoexcitation does not lead to any significant luminescence. To rationalize this original dual photophysical behavior, we have performed time-dependent density functional theory (TD-DFT) calculations on C60+ to investigate the potential energy surfaces of the relevant electronic states, completed by the simulations of vibrationally resolved absorption and emission spectra. The proposed photophysical pathways shed light on the experimental measurements: The near-IR laser excitation populates the 11th doublet excited state (D11) that decays to the lowest first bright excited state D5, from which photoluminescence is predicted. Indeed, D5 is largely separated from the lower electronic states (D0-D4). Thus, D5 behaves effectively as the first excited state, while the D0-D4 set of states act as the electronic ground state. In addition, there are no low-lying conical intersections between D5 and lower excited states energetically accessible upon near-IR excitation that can provide efficient nonradiative decay channels for this state, leaving radiative decay as the most likely deactivation pathway. However, a sloped conical intersection between D5 and D4 was located around 2.9 eV above D0. While it is too high in energy to be accessible upon near-IR excitation, it provides a funnel for efficient nonradiative decay down to the ground state (D0) accessible upon UV light excitation. Thus, the photophysics of C60+ is controlled by the ability to access this funnel: Upon near-IR excitation, the system fluoresces because the funnel for nonradiative decay cannot be reached, while UV irradiation provides a different route by opening up a radiationless decay channel via this funnel, accounting for the absence of fluorescence.

Wave Function Control of Charge-Separated Excited-State Lifetimes.

Control of excited-state processes is crucial to an increasing number of important device technologies that include displays, photocatalysts, solar energy conversion devices, photovoltaics, and photonics. However, the manipulation and control of electronic excited-state lifetimes and properties continue to be a challenge for molecular scientists. Herein, we present the results of ground-state and transient absorption spectroscopies as they relate to magnetic exchange control of excited-state lifetimes. We describe a novel mechanism for controlling these excited-state lifetimes that involves varying the magnetic exchange interaction between a stable organic radical and the unpaired electrons present in the open-shell configuration of a charge-separated excited state. Specifically, we show that the excited-state lifetime can be controlled in a predictable manner based on an a priori knowledge of the pairwise magnetic exchange interactions between excited-state spins. These magnetic exchange couplings affect the excited-state electronic structure in a manner that introduces variable degrees of spin forbiddenness into the nonradiative decay channel between the excited state and the electronic ground state.

Tetraphenylpyrazine Based AIE Luminogens: Unique Excited State Decay and Its Application in Deep‐Blue Light‐Emitting Diodes

AbstractCarbazole‐modified tetraphenylpyrazine (TPP) derivatives TPP‐Cz, TPP‐PhCz, TPP‐2Cz, and TPP‐2PhCz are prepared with different patterns by inserting a π‐bridge and adopting two‐armed forms to produce aggregation‐induced emission (AIE)‐type deep‐blue emitters for organic light‐emitting diode (OLED) applications. Systematic spectral analysis and detailed theoretical calculation of these TPP derivatives reveal their special excited state behaviors. Unlike the traditional AIE unit, which features enhanced emission from solution to aggregate with the nonradiative decay channel blocked, a tenfold increase in the radiative decay rate of these TPP‐based AIE luminogens (AIEgens) is observed from the solution to film states. The formation of a stable quinone conformation of the TPP center and its peripheral phenyl group in the excited state is the main reason for this behavior. The distribution changes in the total reorganization energy are further integrated, and a feasible molecular design strategy is proposed for the TPP family. Nondoped OLEDs are fabricated, and the AIEgens exhibit good performance with valuable blue emission (x + y &lt; 0.3). The TPP‐Cz‐based optimized devices exhibit more stable external quantum efficiencies and an ideal roll‐off with unchanged Commission Internationale de l'Elcairage (CIE) coordinates of (0.16, 0.11). These findings demonstrate the great potential of TPP with its unique excited state characteristics as a deep‐blue AIEgen.

The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes.

Fluorophores with high quantum yields are desired for a variety of applications. Optimization of promising chromophores requires an understanding of the non-radiative decay channels that compete with the emission of photons. We synthesized a new derivative of the famous laser dye 4-dicyanomethylen-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM), i.e., merocyanine 4-(dicyanomethylene)-2-tert-butyl-6-[3-(3-butyl-benzothiazol-2-ylidene)1-propenyl]-4H-pyran (DCBT). We measured fluorescence lifetimes and quantum yields in a variety of solvents and found a trend opposite to the energy gap law. This motivated a theoretical investigation into the possible non-radiative decay channels. We propose that a barrier to a conical intersection exists that is very sensitive to the solvent polarity. The conical intersection is characterized by a twisted geometry which allows a subsequent photoisomerization. Transient absorption measurements confirmed the formation of a photoisomer in unpolar solvents, while the measurements of fluorescence quantum yields at low temperature demonstrated the existence of an activation energy barrier.

Non-radiative decay of an eumelanin monomer: to be or not to be planar.

In order to understand the photoprotection process in eumelanin, it is imperative to understand the photoprocesses in its monomers. Eumelanin is a polymeric structure made of di-hydroxyindole (DHI) as the basic motif. There have been studies on the ground and low-lying excited state potential energy surfaces (PESs) and a few of the important modes have been identified in the eumelanin monomer. However, to properly depict the fate of a molecule after an initial photoexcitation, it is important to look at the dynamical picture and in this work, we have studied the excited state dynamics of a eumelanin monomer. We observe that there are planar OH elongation modes that can be important for the de-excitation mechanism. There are also non-planar modes that distort the phenyl ring of the DHI molecule. In the excited state dynamics, it is the non-planar modes that are more relevant to the non-radiative deactivation process of the monomer. We further notice that due to the non-planarity in the molecules along the deactivation path, the excited states involved in the processes are mixed ππ* and πσ* in nature. Furthermore, it is noticed that this deactivation process occurs well below a ps timescale.

Functionalizing plasmonic nanoparticles through adding a shell to improve electronic properties of c-Si thin-film solar cells

Embedding plasmonic nanoparticles (p-NPs) inside the solar cell’s active layer is capable of enhancing active layer optical absorption; however, such inclusion has some detrimental effects on the electronic properties of the solar cells. In addition, p-NPs are highly catalytic, their presence enables other non-radiative decay channels besides generation of electron–hole pairs, and the electrons usually get absorbed by these p-NPs. This results in the unfavorable fact that the potential enhancement in the carrier generation rate and the generated current is no longer in line with the enhancement in the optical absorption. In this paper, we propose to functionalize p-NPs by adding a dielectric or semiconductor shell, to passivate the p-NP without deteriorating scattering and/or plasmonic effects. Ag@SiO2 and Ag@TiO2 core–shell p-NPs have been intensely studied using extensive computational electromagnetic simulations to model the spectral response of the active layer’s optical absorption as well as electronic properties as a function of both shell composition and thickness. It is shown that a 5 nm TiO2 shell is apt to optically passivate the p-NP without any reduction in optical absorption, while improving the short circuit current density (J sc ) of the thin-film solar cell by 33.3%.