Bulk Defects Research Articles

Influence of surface damage and bulk defects on the interstrip isolation of p-type silicon strip sensors

Silicon strip sensors of upcoming tracking detectors in high luminosity colliders usually consist of a p-doped bulk with n-type strip implants. The general consensus is that such a design requires an additional interstrip isolation structure such as a p-stop implant. If there is no additional implant between the strips, it is expected that the strip isolation will be insufficient. Before irradiation, impurities and defects in the material lead to positive charge in the oxide and Si/SiO_2 interface which attracts electrons from the bulk. Those electrons accumulate just beneath the surface and between the n+ strip or pixel implants, which decreases the interstrip resistance significantly. Ionising radiation introduces even more charge inside the silicon dioxide, which further decreases the interstrip resistance. Contrary to that expectation of a decreasing interstrip resistance due to irradiation, a high interstrip resistance was sometimes observed after proton irradiation. Hence, bulk defects induced by proton irradiation seem to have a non-negligible impact on the strip isolation. Therefore, an irradiation campaign with sensors without any interstrip isolation implant has been performed. The use of sensors without isolation structures provides deeper insight into the dominant isolation effects. The sensors' performance is first evaluated before irradiation. Afterwards, a set of sensors is irradiated with different particles in order to systematically introduce a mixture of surface and bulk defects. This enables the distinction and leads to a better understanding of the different effects. Finally, a combined TCAD model is derived which is able to describe the beneficial effect of bulk defects and the complicated interplay between surface and bulk damage.

Numerical investigation on performance improvement of WS2 thin-film solar cell with copper iodide as hole transport layer

In the present work, device modeling of tungsten disulfide-based thin-film solar cell with copper iodide as hole transport layer has been performed using the Solar Cell Capacitance Simulator in One Dimension software program (SCAPS-1D). The SCAPS-1D simulator is also utilized to investigate the photovoltaic performances of tungsten disulfide (WS2)-based solar cells. This numerical study provides a comparison of the performances between the reference WS2-based solar cell structure without hole transport layer (HTL) consisting of Al/FTO/CdS/WS2/Ni and the proposed configuration of Al/FTO/CdS/WS2/CuI/Ni. The influences of thickness, doping density, bulk defect density, defect density at buffer/absorber and absorber/HTL interfaces, operating temperature, series and shunt resistances, and back surface recombination velocity on the solar cell output parameters have also been analyzed. It is revealed that the carrier recombination at the back side has notable effects on the overall photovoltaic performances of the WS2 heterojunction solar cell without HTL. The carrier recombination loss at the back surface can be reduced by incorporation of an ultra-thin 0.1 μm copper iodide (CuI) HTL into the reference WS2-based solar cell and thus improves the overall performances of the proposed photovoltaic device. The conversion efficiency of 22.09% has been found for the reference WS2 solar cell without HTL. On the other hand, the efficiency of the proposed solar cell with CuI HTL has been obtained to be 29.87% at the optimized device structure. Therefore, these findings may contribute insightful approach to fabricate viable, inexpensive, and highly efficient heterojunction thin-film solar cell.

Alleviating halide perovskite surface defects

Alleviating halide perovskite surface defects

Fluorine Passivation of Defects and Interfaces in Crystalline Silicon.

Defects and impurities in silicon limit carrier lifetimes and the performance of solar cells. This work explores the use of fluorine to passivate defects in silicon for solar cell applications. We present a simple method to incorporate fluorine atoms into the silicon bulk and interfaces by annealing samples coated with thin thermally evaporated fluoride overlayers. It is found that fluorine incorporation does not only improve interfaces but can also passivate bulk defects in silicon. The effect of fluorination is observed to be comparable to hydrogenation, in passivating grain boundaries in multicrystalline silicon, improving the surface passivation quality of phosphorus-doped poly-Si-based passivating contact structures, and recovering boron-oxygen-related light-induced degradation in boron-doped Czochralski-grown silicon. Our results highlight the possibility to passivate defects in silicon without using hydrogen and to combine fluorination and hydrogenation to further improve the overall passivation effect, providing new opportunities to improve solar cell performance.

Enhancing gate turn-off thyristor blocking characteristics by low temperature defect passivation technology

In the past, gate turn-off (GTO) thyristors were commonly used to either increase the length of the drift region or reduce the doping concentration to increase high-voltage and high-power applications. However, this results in an on-resistance (R on) increase. In this study, we applied a supercritical fluid (SCF) treatment to devices which has the advantage of high permeability and low-temperature processing to passivate SiC-GTO bulk defects. After the proposed defect passivation, the breakdown voltage has been improved by 8% without increasing on-state resistance. In addition, the leakage current has also been suppressed more than 30% in average. This study also uses electrical analysis to understand the characteristics of the devices after SCF treatment, and then discusses the passivation mechanism of materials of the devices from this treatment.

Prediction of the charge carriers stationary distribution in the active region of the p-i-n structures by the perturbation theory methods

The p-i-n diode is an electronic device that is widely used for switching a microwave signals. The theory of the p-i-n diode is based on linear mathematical models that satisfactorily explain the diodes switching properties at low microwave power levels. The developed methods for modeling the corresponding devices on p-i-n diodes turned out to be untenable when studying the properties of diodes and diode structures under the with high-power microwave signals (typical for high-power switches and protective devices). Here are faced with the need to take into account the mutual influence of diffusion-drift, wave, thermal processes, in which the nonlinear components of the mathematical models will dominate. The development of the computer technology and the corresponding mathematical methods (for example, the perturbation theory methods) determines the possibility of improving the existing p-i-n diodes mathematical models and the possibility of the new approaches developing to the analysis of the nonlinear processes in p-i-n diodes and similar electronic devices. The goal of this paper is to improve the mathematical model and methods for predicting the electron-hole plasma stationary distribution in the active region of surface-oriented p-i-n structures based on the use of the boundary functions method. The mathematical model of the electron-hole plasma stationary distribution in the integrated surface-oriented p-i-n structures active region is constructed in the form of the nonlinear singularly perturbed boundary value problem for the system of equations of the charge carriers current continuity and Poisson. An approximate solution of the corresponding boundary value problem is found in the form of the asymptotic series leading terms in powers of a small parameter. A scheme for finding the problem solution is proposed, which automatically includes the classical formulations of problems for modeling the p-i-n structures characteristics and allows you to make significant amendments to the solution. This ensures an increase in the level of adequacy of modeling and understanding of the features of a number of physical processes (diffusion-drift, recombinant, injection) in the p-i-n diodes active region. We consider the proposed approach a promising tool for studying nonlinear thermal, diffusion-drift, generation-recombination stationary and non-stationary processes occurring in the p-i-n structures elements under the action of the external microwave radiation, and predicting new physical effects in the studied systems, for example, due to the influence of local surface and bulk defects on the p-i-n structures characteristics.

Metal organic framework-templated fabrication of exposed surface defect-enriched Co3O4 catalysts for efficient toluene oxidation

Exposed surface defect-enriched Co3O4 catalysts derived from metal organic framework (MOF) were fabricated by the promotion of surface Mn species for toluene oxidation. The incorporation of Mn species into Co3O4 surface lattice could give rise to the local lattice distortion in spinel structure, resulting in highly exposed surface defect rather than bulk defect. More Co3+ species were also exposed on the surface of MnOx/Co3O4 samples owing to the electron transfer from Co to Mn species by the occupation of surface Mn in octahedral Co3+ sites. Accordingly, the low-temperature reducibility and high mobility of lattice oxygen were significantly improved in virtue of the highly exposed surface defect and predominately surface Co3+ sites, thus promoting the catalytic activity and stability for toluene oxidation. Moreover, the toluene conversion decreased with the increase of weight hourly space velocity (WHSV). In situ DRIFTS results confirmed the continuous oxidation process for toluene degradation, and the conversion of benzoate into maleic anhydride should be the rate-controlling step.

High efficiency ETM-free perovskite cell composed of CuSCN and increasing gradient CH3NH3PbI3

To enhance device performance and reduce fabrication cost, a series of electron transporting material (ETM)-free perovskite solar cells (PSCs) is developed by TCAD Atlas. The accuracy of the physical mode of PSCs is verified, due to the simulations of PEDOT:PSS–CH3NH3PbI3–PCBM and CuSCN–CH3NH3PbI3–PCBM p–i–n PSCs showing a good agreement with experimental results. Different hole transporting materials (HTMs) are selected and directly combined with n-CH3NH3PbI3, and the CuSCN–CH3NH3PbI3 is the best in these ETM-free PSCs. To further study the CuSCN–CH3NH3PbI3 PSC, the influences of back electrode material, gradient band gap, thickness, doping concentration, and bulk defect density on the performance are investigated. Energy band and distribution of electric field are utilized to optimize the design. As a result, the efficiency of CuSCN–CH3NH3PbI3 PSC is achieved to be 26.64%. This study provides the guideline for designing and improving the performances of ETM-free PSCs.

Co-catalyst-free large ZnO single crystal for high-efficiency piezocatalytic hydrogen evolution from pure water

Piezocatalytic materials have been widely used for catalytic hydrogen evolution and purification of organic contaminants. However, most studies focus on nano-size and/or polycrystalline catalysts, suffering from aggregation and neutralization of internal piezoelectric field caused by polydomains. Here we report a single crystal ZnO of large size and few bulk defects crafted by a hydrothermal method for piezocatalytic hydrogen generation from pure water. It is noteworthy that single-side surface areas of both original as-prepared ZnO and Ga-doped ZnO bulk crystals are larger than 30 cm2. The high quality of ZnO and Ga-doped ZnO bulks are further uncovered by high-resolution transmission electron microscope (HRTEM), photoluminescence (PL) and X-ray diffraction (XRD). Remarkably, an outstanding hydrogen production rate of co-catalyst-free Ga-doped ZnO bulk crystal (i.e., a maximum rate of 5915 μmol h−1 m−2) is observed in pure water triggered by ultrasound in dark, which is over 100 times higher than that of its powder counterpart (i.e., 52.54 μmol h−1 m−2). The piezocatalytic performance of ZnO bulk crystal is systematically studied in terms of varied exposed crystal facet, thickness and conductivity. Different piezocatalytic performances are attributed to magnitude and distribution of piezoelectric potential, revealed by the finite element method (FEM) simulation. The density functional theory (DFT) calculations are employed to investigate the piezocatalytic hydrogen evolution process, indicating a strong H2O adsorption and a low energy barrier for both H2O dissociation and H2 generation on the stressed Zn-terminated (0001) ZnO surface.

Multimodal host\u2013guest complexation for efficient and stable perovskite photovoltaics

Formamidinium lead iodide perovskites are promising light-harvesting materials, yet stabilizing them under operating conditions without compromising optimal optoelectronic properties remains challenging. We report a multimodal host–guest complexation strategy to overcome this challenge using a crown ether, dibenzo-21-crown-7, which acts as a vehicle that assembles at the interface and delivers Cs+ ions into the interior while modulating the material. This provides a local gradient of doping at the nanoscale that assists in photoinduced charge separation while passivating surface and bulk defects, stabilizing the perovskite phase through a synergistic effect of the host, guest, and host–guest complex. The resulting solar cells show power conversion efficiencies exceeding 24% and enhanced operational stability, maintaining over 95% of their performance without encapsulation for 500 h under continuous operation. Moreover, the host contributes to binding lead ions, reducing their environmental impact. This supramolecular strategy illustrates the broad implications of host–guest chemistry in photovoltaics.

Imaging CdCl2 defect passivation and formation in polycrystalline CdTe films by cathodoluminescence

Polycrystalline thin-film solar cells are attractive for low-cost photovoltaics, but their efficiencies are hindered by material quality issues. State-of-the-art CdTe solar cells use ${\mathrm{CdCl}}_{2}$ annealing treatments whose effects are still being discovered at a fundamental level. Here, a series of CdTe samples with different annealing temperatures is investigated with high-resolution hyperspectral cathodoluminescence mapping measured at both room temperature and low temperature on the same microscopic areas. A statistical analysis over a large number of grains is combined with a local analysis at grain boundaries. The results elucidate the dynamic interplay between grain boundary and intragrain defect passivation and formation, in the midst of grain growth. The ${\mathrm{CdCl}}_{2}$ annealing initially contributes to an increase of the grain size and the passivation of both grain boundaries and grain interiors, increasing the overall luminescence and diffusion length. For higher annealing temperatures, a further increase of grain size is counterbalanced by the rise of bulk defects. The results illustrate the tradeoffs that lead to an optimal annealing temperature, as well as new methods for understanding defect passivation and creation in thin film solar cells.

Combined specular and off-specular reflectometry: elucidating the complex structure of soft buried interfaces

Neutron specular reflectometry (SR) and off-specular scattering (OSS) are nondestructive techniques which, through deuteration, give a high contrast even among chemically identical species and are therefore highly suitable for investigations of soft-matter thin films. Through a combination of these two techniques, the former yielding a density profile in the direction normal to the sample surface and the latter yielding a depth-resolved in-plane lateral structure, one can obtain quite detailed information on buried morphology on length scales ranging from the order of ångströms to ∼10 µm. This is illustrated via quantitative evaluation of data on SR and OSS collected in time-of-flight (ToF) measurements of a set of films composed of immiscible polymer layers, protonated poly(methyl methacrylate) and deuterated polystyrene, undergoing a decomposition process upon annealing. Joint SR and OSS data analysis was performed by the use of a quick and robust originally developed algorithm including a common absolute-scale normalization of both types of scattering, which are intricately linked, constraining the model to a high degree. This, particularly, makes it possible to distinguish readily between different dewetting scenarios driven either by the nucleation and growth of defects (holes, protrusionsetc.) or by thermal fluctuations in the buried interface between layers. Finally, the 2D OSS maps of particular cases are presented in different spaces and qualitative differences are explained, allowing also the qualitative differentiation of the in-plane structure of long-range order, the correlated roughness and bulk defects by a simple inspection of the scattering maps prior to quantitative fits.

(Invited) Interface Treatment Related Defects During Ge Gate Stack Formation

Germanium as a high mobility channel material is currently of considerable interest since Ge has both higher electron and hole mobility as compared to silicon (1). The deposition of high-k dielectrics on Ge has been a significant challenge because of high interface defects density, Dit (2). By considering the interface reaction kinetics, thermal budget various atomic layer deposition (ALD) schemes and interface treatments can be identified to get a stable dielectric with a robust interface. However, understanding of the interface kinetics and defect distribution into gate stack and/or Ge is still limited.In this work, we report the impact of different interface treatments on the p type Ge prior to any high-k layer deposition on defect generation. Ge surface was oxidized by a controlled chemical oxidation, slot-plane-antenna plasma oxidation and oxidation through vapor O3 treatment before ALD deposition of 1nm Al2O3/3.5nm ZrO2 for gate stack formation. These devices were characterized to evaluate the interface and possible bulk defects by deep level transient spectroscopy (DLTS), capacitance spectroscopy, conductance method in addition to standard I-V and C-V measurements. DLTS has the advantage to have the spectrum comparison among the interface treatments. Signature of these spectra can reveal the difference, which is more accurate than the defects estimated by Conductance method. DLTS also provides the signature of slow traps (~1ms) (Fig. 1) originating from the bulk or interface depending on the type of GeOx formation.Furthermore, we evaluate the defect distribution when the gate stack was subjected to a slot-plane antenna plasma oxidation prior to metal deposition. A TiN/Hf1-xZrxO2/Al2O3/Ge gate stack with six different Zr content was investigated (Fig. 2). Al2O3 was used to impede the Ge diffusion into the gate stack. Interface state density (Dit) and C-V hysteresis show that the mid-gap Dit tend to increase with decrease in EOT, possibly due to the undesirable native oxide formation on Ge.The author would like to thank Drs. Y.M. Ding (Western Digital Corporation, Shanghai, China), M.N. Bhuyian (Globalfoundries, Malta, NY, USA), K.L. Ganapathi (Indian Institute of Technology Madras, India), N. Bhat, (Indian Institute of Science, Bangalore, India) and K. Tapily, R. D. Clark, S. Consiglio, C. S. Wajda, G. Nakamura, and G. J. Leusink of TEL Technology Center, America, Albany, NY, for their help in this work. References Arimura et al, IEDM Technical Digest, (2020)N. Bhuyian et al, ECS Journal of Solid-St. Sci. and Tech., vol. 7(2), N1-N6, (2018)G. Kolla et al, J. Vac. Sci. Technol. B, 36(2), 021201 (2018)Ding et al, IEEE Trans. on Dev. and Materials Reliability, 17(2), 349-354, (2017)Ding, et al, J. of Vac. Sci. and Technol. B, 34(2), 021203, 2016. Figure 1

Interface and defect engineering enable fast and high-efficiency Li extraction of metatitanic acid adsorbent

Considering the striking theoretical Lithium (Li) uptake capacity, environmental benignity and low cost, metatitanic acid (H2TiO3, abbreviated to HTO) is considered to be one of the most promising lithium ion sieve (LIS) adsorbent for liquid-phase Li extraction technology. However, the discouraging adsorption kinetics seriously hampers its industrial application. Herein, the traditional HTO-LIS is promoted by the combined strategies of pore-structure construction, surface heteroatom modification and alien Zn ion bulk doping, which ameliorates the surface characterization of the HTO adsorbent towards fast Li+ capturing from the solution, facilitating the activation and replacement of Li+ on the interface. Further, the oxygen bulk defect originated from Zn doping accelerates the Li+ transfer in solid-phase via the depressed diffusion energy barrier. The interfacial modification and defect engineering synergistically cooperate to extremely speed up the Li extraction process that the Li uptake rate of the optimized sample (PN-HZTO-0.04) increases to 457% compared to the pristine HTO-0 adsorbent. Remarkably, in the optimized Solid/Liquid ratio adsorption test, the adsorption efficiency of above 96% are achieved in 2 h, without obvious capacity degradation and Ti dissolution loss during adsorption/desorption cycles, representing excellent recycling ability.

New Insights into the Bulk and Surface Defect Structures of Ceria Nanocrystals from Neutron Scattering Study

Neutron diffraction and pair distribution function studies coupled with Raman spectroscopy have successfully unraveled the detailed oxygen defect structures of ceria nanocubes and nanorods. Two types of defect sites are revealed for the ceria nanocrystals: surface and bulk defects. It is proposed that the surface oxygen defects in both types of CeO2 nanocrystals are predominantly the partially reduced Ce3O5+x, with the bulk defect structures dominated by interstitial Frenkel-type oxygen vacancies. Ceria nanorods possess much higher concentration of surface oxygen defects relative to the nanocubes, albeit with only slightly higher concentration of bulk Frenkel-type oxygen vacancies. Upon annealing the nanorod sample at 600 °C under vacuum (∼10–4 to 10–5 mbar), a partially reduced ceria phase with long-range oxygen vacancy ordering (Ce3O5+x) has been observed experimentally for the first time. This intriguing observation that surface defect phases can take on ordered defect sublattices under certain conditions is of great value in understanding the temperature-dependent catalytic performance of ceria nanocrystals. Furthermore, a drastic decrease of the surface vacancies in the ceria nanocrystals is observed upon exposure to SO2, especially for the nanorods, a likely origin for the sulfur poisoning effect on ceria-based materials. This study suggests that tailoring surface morphology is a promising strategy to control defect properties of ceria nanomaterials. It also provides fundamental insights to stabilize surface oxygen defects in CeO2 nanocrystals to achieve high redox performance under corrosive environments such as under SO2/SOx exposure.

Functionalized carbon nanotube bridge interface drove Bi2O2CO3/g-C3N4 S-scheme heterojunction with enhanced visible-light photocatalytic activity

• FCNT-Bi 2 O 2 CO 3 /30% g-C 3 N 4 S-scheme heterostructure was easily prepared by one-step hydrothermal method. • The exposure of crystal planes and bulk defects improve the degradation performance of organic pollutant. • The actual water matrix (such as the Yangtze River and the Yellow River) has little effect on FCNT-Bi 2 O 2 CO 3 /30% g-C 3 N 4 . Appropriate interfacial contact and defect engineering in heterojunction materials play a critical role to improve photocatalytic activity. In this article, a carbon bridge connected Bi 2 O 2 CO 3 /g-C 3 N 4 step-scheme heterojunction photocatalysts were fabricated by a simple one-step hydrothermal method. Among them, the functionalized carbon nanotube as a bridge has excellent electrochemical energy storage performance and favorable stability. Under visible light irradiation, the FCNT-Bi 2 O 2 CO 3 /30% g-C 3 N 4 exhibited the best photocatalytic activity for the degradation tetracycline with 96%. The enhanced photocatalytic activity could be due to the doping of acidified nanotubes causing shallow potential defects in the heterostructure, exposing the {0 0 1} crystal plane and causing bulk defects, which in turn facilitate the separation of photogenerated charge carriers. Moreover, the obtained FCNT-Bi 2 O 2 CO 3 /g-C 3 N 4 step-scheme heterojunction photocatalysts exhibited better activity than pure g-C 3 N 4 and Bi 2 O 2 CO 3 . In addition, the formation and practical application of composite heterostructures are discussed in detail. This investigation provides new insight for designing and constructing novel S-scheme heterojunction photocatalysts.

Foamer-Derived Bulk Nitrogen Defects and Oxygen-Doped Porous Carbon Nitride with Greatly Extended Visible-Light Response and Efficient Photocatalytic Activity.

Constructing bulk defects and doping are feasible ways to essentially narrow the band gap and improve the light absorption of photocatalysts. Herein, inspired by bread foaming, the foaming agent azoformamide or azodicarbonamide (AC) was introduced during the thermal polymerization of urea. In the polymerization process, a large number of bubbles produced by AC decomposition seriously interfered with the polymerization of urea, resulting in the breaking of the hydrogen bonds and van der Waals interaction in carbon nitride, distortion of its structure, and partial oxidation, thus forming a series of porous carbon nitrides U/ACx (x is the ratio of AC to urea; where x = 0.25, 0.5, and 1) with bulk N defects and O doping. Its band gap was reduced to 1.91 eV and the absorption band edge was greatly extended to 650 nm. The optimal U/AC0.5 exhibits the highest visible light photocatalytic hydrogen production rate of about 44.7 μmol·h-1 (10 mg catalysts) and shows superior photocatalytic performance for the oxidation of diphenylhydrazine to azobenzene, with conversion and selectivity of almost 100%, and is one of the most active defective carbon nitrides, especially under long-wavelength (λ ≥ 550 nm) light irradiation. It paves the way for the design of highly efficient and wide-spectral-response photocatalysts.

Synergistic Effect of RbBr Interface Modification on Highly Efficient and Stable Perovskite Solar Cells.

Compact TiO2 films are one of the most widely used electron transport layers (ETLs) in planar perovskite solar cells (PSCs). However, the performance of the PSC device is controlled by the comprehensive qualities of the functional layers and their bilateral surfaces. In this work, the alkali metal halide of RbBr as the interfacial modifier is introduced into the interface of the TiO2 ETL and perovskite absorber. By spin-coating the proper content of RbBr, the surface of the TiO2 film consisting of smooth morphology and low density of oxygen-deficiency defect is readily obtained. The perovskite layer successively fabricated on the RbBr-modified TiO2 film demonstrates large grain size, low surface roughness, and low bulk defect density, which enhances the electron extraction and decreases nonradiation recombination. By virtue of the modulation of the perovskite crystal quality and the passivation of the interfacial defects, the light-harvesting efficiency of the corresponding device is increased to 21.15 from 19.21% for the PSC without a RbBr insertion layer. More importantly, the passivation strategy enables impressive device stability by retaining 90% of its initial efficiency in an ambient environment for 500 h. This study provides a promising and feasible strategy to regulate surface passivation engineering and simultaneously facilitate the perovskite crystal growth for the achievement of efficient and stable perovskite photovoltaics.

Graphene quantum dot-embedded perovskite photodetectors with fast response and enhanced sensitivity through bulk defect passivation

Graphene quantum dots (GQDs) synthesized by single phase solution chemistry are embedded in metal halide perovskite (MHP) films because they can act as passivating defects that are present throughout the MHP film, not only at the interface but also throughout the bulk of the film. The perovskite photodetectors composed of indium-doped tin oxide/SnO2/MHP with embedded GQDs/poly triarylamine/Au have the reduced dark current, increased detectivity, and fasted response speed due to lower trap density throughout the bulk MHP layer.

Study of defect properties and recombination mechanism in rubidium treated Cu(In, Ga)Se2 solar cells

Heavy alkali-metal treatment of Cu(In,Ga)Se2 (CIGSe) absorbers has been emerging as a key process for achieving over 23% high conversion efficiencies in CIGSe solar cells. Here, we investigate the effect of rubidium fluoride post-deposition treatment (RbF-PDT) on the electronic and carrier recombination properties of narrow bandgap (narrowgap) gap and wide bandgap (widegap) CIGSe solar cells using thermal admittance spectroscopy (TAS), transient photocapacitance spectroscopy (TPC), as well as time-resolved photoluminescence (TRPL). We find that the activation energy of the main capacitance step in TAS spectra of narrowgap and widegap CIGSe solar cells reduces after RbF-PDT. On the other hand, capacitance–voltage (C–V) and temperature-dependent current–voltage (IVT) measurements demonstrate that the built-in potential, as well as the activation energy Ea, increases upon RbF-PDT both for narrowgap and widegap samples, pointing to reduced interface recombination. TPC revealed an appreciable reduction of the optical response of bulk defects in the narrowgap and widegap CIGSe, suggesting improvement of bulk properties after RbF treatment. TRPL confirmed that RbF-PDT significantly reduces carrier recombination in the bulk of narrowgap and widegap CIGSe absorbers and at the surface, leading to extended carrier lifetimes. Analysis of open-circuit voltage (VOC) losses due to nonradiative recombination in the bulk of the CIGSe showed a strong correlation between enhanced carrier lifetime and improved VOC for narrow gap CIGSe cells. In contrast, although we observed a substantial decrease of VOC losses in widegap CIGSe bulk, the analysis indicated that the key to photovoltaic performance enhancement is improved interface quality.