Deep Level Defects Research Articles

The Effect of Nanopipes and an Inserted n‐AlGaN Interlayer on GaN Avalanche Photodiodes Performance

The effect of nanopipe defects on the device performance of Gallium nitride (GaN) avalanche photodiodes (APDs) is investigated and the influence mechanism is analyzed. It is discovered that nanopipes can incorporate more carbon impurities, resulting in the introduction of more deep energy level defects into the epitaxial layers. This causes an increase in device leakage and challenges in distinguishing between light current and dark current. It is found that an inserted n‐AlGaN interlayer can effectively block nanopipes and improve device performance significantly.

High transparent and stability indium praseodymium oxide thin-film transistors with tungsten doping by solution method

Indium-oxide-based thin-film transistors are widely investigated and exhibit higher carrier mobility than amorphous silicon. Lanthanide-doped Indium oxide TFTs show relatively high negative bias illumination stress (NBIS) stability but at the cost of mobility. To improve the NBIS stability by the solution method, we doped Tungsten (W) into Praseodymium-doped Indium oxide (InPrO) and fabricated InPrWO TFT. We proposed that W doping could densify the films and suppress oxygen vacancy. With the increase of W doping concentration from 0 to 3 mol%, the contact angle of precursor solutions first decreased and then increased, reaching minimums of ∼13° at 1 mol%. When the W doping concentration increased from 0 to 1 mol%, the density of films increased from 6.155 to 6.479 g/cm3. While doping concentration increased from 1 to 3 mol%, the density of films decreased. Transmittance of InPrWO films was higher than 90 % from 300 to 800 nm. The localized defects of InPrWO films were investigated by μ-PCD. With 1 mol% W doping, deep-level and shallow-level defects were relatively the least. XPS result revealed that W was successfully doped into the films. Besides, the oxygen vacancy ratio first decreased and then increased when the W doping concentration increased. InPrWO film with 1 mol% W doping had the least oxygen vacancy ratio, resulting in the highest stability. The TFT fabricated with optimal 1 mol% W doped InPrWO film showed excellent electrical characteristics (μsat = 5.4 cm2/Vs, Vth = -0.3 V, Ion/Ioff = 8.0 × 105, and SS = 0.30 V/dec). With the W doping concentration increased, the NBIS stability first increased and then decreased, having minimum shift ΔVth = -2.1 V at 1 mol%. We improved the quality of films and NBIS stability of TFT by doping W into InPrO and appropriate post-processing, satisfying the development trend of high transparency and high stability TFTs for future displays.

Achieving highly efficient kesterite solar cells using simultaneous surface Ge substitution and rear interface engineering strategies

The progress in the device performance of kesterite-based thin-film solar cells (TFSCs) have been stagnant due to unstable rear contact properties and large open circuit voltage (Voc)-deficit characteristics. Several individual strategies have been developed to solve these issues. In this work, we investigate the simultaneous impact of Ge substitution and rear interface engineering with a MoOx intermediate layer on Mo back contact. The simultaneous application of both strategies delivers a synergetic effect, improving microstructure, Voc-deficit, band-tailing states, and device parameters and reducing Sn-related deep-level defects, resulting in enhanced power conversion efficiency (from 8.1 to 11.55%). This effective strategy offers new insight and a way to solve unstable rear contact properties and large Voc-deficit, further improving the device performances of kesterite-based TFSCs.

Cs-treatments in Kesterite Thin-Film Solar Cells for Efficient Perovskite Tandems.

Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells are an attractive choice for a bottom cell of the low-cost and environmental tandem solar cells with perovskite. However, the progress in developing efficient perovskite/CZTSSe tandem solar cells has been hindered by the lack of high performance of the CZTSSe bottom cell. Here, an efficient CZTSSe bottom cell is demonstrated by adopting a facile and effective CsF treatment process. It is found that the CsF treatment not only facilitates grain growth and improves phase homogeneity by suppressing the detrimental deep-level defects and secondary phases, but also induces larger band bending and stronger drift force at the P-N junction. As a result, the carrier extraction/transport can be effectively accelerated, while reducing the interfacial recombination. These combined effects eventually result in a significant performance enhancement from 8.38% to 10.20%. The CsF-treated CZTSSe solar cell is finally applied to the mechanically-stacked perovskite/CZTSSe 4-terminal tandem cell by coupling a semi-transparent perovskite top cell, which exhibits the highest reported tandem efficiency of 23.01%.

Comparative of HPHT and CVD diamond: performance and defect analysis for alpha radiation detector

Currently, the high-purity single crystal diamond preparation is still a challenging task, which restricts the application of diamond in electronics. In this paper, the chemical vapor deposition (CVD) IIa type single crystal diamond was prepared on the IIa type high pressure high temperature (HPHT) substrate by combining the chamber design with the plasma purifying technology, and the performance of diamond detectors using both IIa type single crystal diamonds were compared based on the defect analysis. The dislocations in diamonds were directly observed by synchrotron radiation X-ray white-beam topography. The CVD diamond shows the comparatively low dislocation density resulting from the high-quality HPHT diamond substrate. No observable NV impurity could be found in photoluminescence (PL) spectrum. The trace impurity of substitutional nitrogen (Ns) was characterized by electron paramagnetic resonance (EPR). It shows the very low concentration in the CVD diamond (2.1 ppb) compared with the several tens ppb in HPHT diamond. This value is comparable with the electronic-grade diamond reported by Element Six. Furthermore, both of the HPHT and CVD single crystal diamonds were packaged as the α-particle radiation detectors with the typical sandwich structure and used Ni/Al (50 nm/500 nm) as metal electrodes. The energy resolution of HPHT and CVD diamond detectors were 2.04% and 0.86%, respectively. Based on Schottky contact and defect regulation, at 0 voltage, the CVD diamond detector achieved response of α-particle radiation and the charge collection efficiency (CCE) was 10.76%. Under positive voltage, the CCE of HPHT and CVD diamond detectors were 38.11% and 86.65%, respectively. The deep level trapping effect of Ns impurities on charge carriers resulted in low CCE of HPHT diamond detector. The spatial polarization effect caused by defects leaded to the formation of an internal electric field, which was the main reason affecting the transport of charge carriers in CVD diamond.

Synergetic Regulation of Interface Defects and Carriers Dynamics for High-Performance Lead-Free Perovskite Solar Cells.

Severe nonradiative recombination and open-circuit voltage loss triggered by high-density interface defects greatly restrict the continuous improvement of Sn-based perovskite solar cells (Sn-PVSCs). Herein, a novel amphoteric semiconductor, O-pivaloylhydroxylammonium trifluoromethanesulfonate (PHAAT), is developed to manage interface defects and carrier dynamics of Sn-PVSCs. The amphiphilic ionic modulators containing multiple Lewis-base functional groups can synergistically passivate anionic and cationic defects while coordinating with uncoordinated Sn2+ to compensate for surface charge and alleviate the Sn2+ oxidation. Especially, the sulfonate anions raise the energy barrier of surface oxidation, relieve lattice distortion, and inhibit nonradiative recombination by passivating Sn-related and I-related deep-level defects. Furthermore, the strong coupling between PHAAT and Sn perovskite induces the transition of the surface electronic state from p-type to n-type, thus creating an extra back-surface field to accelerate electron extraction. Consequently, the PHAAT-treated device exhibits a champion efficiency of 13.94% with negligible hysteresis. The device without any encapsulation maintains 94.7% of its initial PCE after 2000h of storage and 91.6% of its initial PCE after 1000h of continuous illumination. This work provides a reliable strategy to passivate interface defects and construct p-n homojunction to realize efficient and stable Sn-based perovskite photovoltaic devices.

In-doping collaboratively controlling back interface and bulk defects to achieve efficient flexible CZTSSe solar cells

Focusing on the low open circuit voltage (VOC) and fill factor (FF) in flexible Cu2ZnSn(S,Se)4 (CZTSSe) solar cells, indium (In) ions are introduced into the CZTSSe absorbers near Mo foils to modify the back interface and passivate deep level defects in CZTSSe bulk concurrently for improving the performance of flexible device. The results show that In doping effectively inhibits the formation of secondary phase (Cu(S,Se)2) and VSn defects. Further studies demonstrate that the barrier height at the back interface is decreased and the deep level defects (CuSn defects) in CZTSSe bulk are passivated. Moreover, the carrier concentration is increased and the VOC deficit (VOC,def) is decreased significantly due to In doping. Finally, the flexible CZTSSe solar cell with 10.01% power conversion efficiency (PCE) has been obtained. The synergistic strategy of interface modification and bulk defects passivation through In incorporation provides a new thought for the fabrication of efficient flexible kesterite-based solar cells.

Photoluminescence of CdTe and CdZnTe compounds doped with 2% selenium

The addition of 2 % of selenium in CdTe and CdZnTe (CZT) exhibited an additional acceptor-bound exciton in photoluminescence (PL). From the PL and inductively coupled plasma mass spectrometer (ICP/MS) analyses, the additional acceptor-bound exciton emission is associated with a Cu impurity in the relatively low-purity (5N) precursor CdSe starting material. In addition, thermal quenching of the acceptor/donor bound exciton emissions do not require a shift to any higher excited states or to the free exciton state. ICP/MS analysis also showed a higher concentration of Sn in CdZnTeSe (CZTS) compared to CdTe and CZT which is known to form a deep level trap at around EC – 0.83 eV. The trapping and de-trapping times indicate that the Sn-related deep trap acts as an electron trapping center. The relatively low electron mobility-lifetime product of CZTS might be correlated with the concentration of Sn in the impure CdSe material. Pulse height spectra using an Eu-152 gamma-ray source was taken for a 2-mm-thick planar CZTS detector. The spectra clearly showed all the expected gamma peaks with energy lower than 344.3 keV.

Neutron radiation induced effects in 4H-SiC PiN diodes

Silicon carbide (SiC) is a wide band gap semiconductor and an attractive candidate for applications in harsh environments such as space, fusion, or future high luminosity colliders. Due to the large band gap, the leakage currents in SiC devices are extremely small, even after irradiation to very high fluences, enabling operation without cooling and at high temperatures. This study investigates the effect of neutron irradiation on 50 μm p-n 4H-SiC diodes using current-voltage, capacitance-voltage, and charge collection efficiency (CCE) measurements up to neutron fluences of 1 × 1016 n eq/cm2. The leakage currents of the investigated devices remained extremely small, below 10 pA at 1.1 kV reverse bias. In the forward bias, a remarkable drop of the current was observed, which was attributed to an increased epi resistivity due to compensation of the epi layer doping by deep-level defects. The CCE was evaluated for alpha particles from a radioactive source, a 62.4 MeV proton beam at the MedAustron ion therapy center and using UV-TCT. The charge collection efficiency in reverse bias was shown to scale directly with the 1 MeV equivalent fluence Φeq as CCE∝Φeq -0.63±0.01. A CCE better than 50% was able to be obtained for fluences up to 1 × 1015 n eq/cm2. Because of the low currents in the forward direction, particle detection was also possible in forward bias, where the CCE was found to be increased relative to reverse bias. Furthermore, a significant dependency on the amount of injected charge was observed, with the CCE surpassing 100% in alpha and UV-TCT measurements, requiring further systematic investigation.

Auxiliary Diagnostic Signal for Deep-Level Detection.

We propose and demonstrate that temperature-dependent curve-fitting error values of the Schottky diode I-V curve in the forward regime can be an auxiliary diagnostic signal as the temperature-scan Capacitance DLTS (CDLTS) signals and helps to work time-efficiently with high accuracy when using the Laplace Transform (LT)-DLTS or Isothermal Capacitance transient spectroscopy (ICTS) method. Using Be-doped GaAs showing overlapping DLTS signals, we verify that the LT-DLTS or ICTS analysis within a specific temperature range around the characteristic temperature Tpeak coincides well with the results of the CDLTS and Fourier Transform DLTS performed within the whole temperature range. In particular, we found that the LT-DLTS signals appeared intensively around Tpeak, and we confirmed it with the ICTS result. The occurrence of the curve fitting error signal is attributed to the relatively increased misfit error by the increased thermal emission from the deep-level trap in the case near the Tpeak, because the applied transport model excludes defect characteristics.

Sulfur-graded kesterite structured film drives improvement of VOC.

Realizing the graded bandgap in absorber layer is very essential for high efficient thin film solar cells. However, such bandgap modification in kesterite-structured Cu2ZnSnSe4 is normally realized via high temperature sulfurization process (above 500°C), which is not only difficult to control the sulfurization depth, but also introduces additional deep defects because of the decomposition of absorber layer at such high temperature. In this study, a low-temperature sulfurization process (150°C) is developed. Such process not only inhibits the decomposition of Cu2ZnSnSe4 films and controls the elemental distribution very well, but also increase the surface bandgap of the absorber layer and form a gradient energy bandgap. Also, the density of deep-level defects in the Cu2ZnSnSe4 layer is reduced. As a consequence, the open circuit voltage of the solar cell is improved by 60 mV. This study paves the way towards the high efficient kesterite solar cell and other solar cells.

Bifunctional Interface Passivation via Copper Acetylacetonate for Efficient and Stable Perovskite Solar Cells.

Manipulating interface defects can minimize interfacial nonradiative recombination, thus increasing the stability and performance of perovskite solar cells (PSCs). Here, copper acetylacetonate [Cu(acac)2] as a passivator is used to treat the interface between Spiro-OMeTAD and perovskite. Owing to the strong chelation, the uncoordinated Pb2+ could react with -C═O/-COH functional groups, firmly anchoring acetylacetonate at this interface or the grain boundaries (GBs) of perovskite films to construct multiple ligand bridges, accompanied by the p-type copper iodide formation with copper substituting lead. Simultaneously, Cu+-Cu2+ pairs transfer electrons from Pb0 to I0, suppressing deep level defects of Pb0 and I0 near the perovskite interface. These can be beneficial to hole-transferring. Moreover, the Schiff base complexes with hydrophobicity, from the reaction of acetylacetonate with perovskite, can lead to tightly packed adjacent perovskite surfaces and self-seal the GBs of the perovskite, inhibiting moisture diffusion for long-term stability. Consequently, the Cu(acac)2-based PSC has achieved more than 24% champion efficiency while retaining ca. 92% of the initial power conversion efficiency after 1680 h of storage.

Photocurrent performance and enhancement of opto-electronic properties of spray pyrolysis deposited ZnO thin films via V-doping

This study reports on the deposition of highly transparent conducting n-type zinc oxide (ZnO) thin films on FTO substrates, via an optimized doping process. Our work is focused on doping zinc oxide with vanadium (V) using spray pyrolysis technique and ensure the synthesis of nanoparticles-shaped ZnO, with an improved optical, microstructural and electrical properties for solar cells applications, as optical window material. Undoped and V-doped ZnO thin films, with careful optimized amounts (2, 4, 6 and 8 at.%), were grown at maintained 550∘C pre-heated substrate during the deposition process, which enables us to obtain nano-sized ZnO particles. We proved that 4 at.% is the optimum V content that enhances the crystallinity of the grown thin film noticeably. With an average transmittance of 80%, the deposited thin films revealed high transparency in the visible domain with a slight decrease in optical transmission which might result from additional scattering. UV-Visible analysis showed that increasing V amounts, a resulting decrease in the energy bandgap ([Formula: see text]) is obtained from 3.26[Formula: see text]eV to 3.17[Formula: see text]eV for 4 at.% of V content. Moreover, deep level defects in zinc oxide can be reduced with vanadium doping and consequently strengthen the UV emission. The UV emission peak intensity rises with increasing V-doping amount then decreases slightly at 8% of V content. The electrical properties measurements showed a decrease in resistivity from 2.8 10[Formula: see text][Formula: see text][Formula: see text][Formula: see text]⋅[Formula: see text]cm to 0.9 10[Formula: see text][Formula: see text][Formula: see text][Formula: see text]⋅[Formula: see text]cm when doping with 4 at.% of V. The crucial effect of the V-doping of ZnO was also demonstrated via the enhancement of carrier mobility that attains 38.5[Formula: see text]cm2/V[Formula: see text]⋅[Formula: see text]s at the optimum vanadium content. The photocurrent analysis revealed much higher visible light absorption in the V-doped zinc oxide thin films than that of undoped film. The photocatalytic activity enhancements are attributed to the lower recombination rate of the photogenerated electron-hole pairs, the narrowed bandgap, yielding a higher photocatalytic performance.

Defect-engineered graphene-on-silicon-carbide platform for magnetic field sensing at greatly elevated temperatures

High-temperature electrical properties of p-type hydrogen-intercalated quasi-free-standing epitaxial Chemical Vapor Deposition graphene on semi-insulating vanadium-compensated on-axis 6H-SiC(0001) and high-purity on-axis 4H-SiC(0001) originate from the double-carrier system of spontaneous-polarization-induced holes in graphene and thermally-activated electrons in the substrate. In this study, we pre-epitaxially modify SiC by implanting hydrogen (H+) and helium (He+) ions with energies ranging from 20 keV to 50 keV to reconstruct its post-epitaxial defect structure and suppress the thermally-developed electron channel. Through a combination of dark current measurements and High-Resolution Photo-Induced Transient Spectroscopy between 300 K and 700 K, we monitor the impact of ion bombardment on the transport properties of SiC and reveal activation energies of the individual deep-level defects. We find that the ion implantation has a negligible effect on 6H-SiC. Yet in 4H-SiC, it shifts the Fermi level from ∼600 meV to ∼800 meV below the minimum of the conduction band and reduces the electron concentration by two orders of magnitude. Specifically, it eliminates deep electron traps related to silicon vacancies in the charge state (2-/-) occupying the h and k sites of the 4H-SiC lattice. Finally, we directly implement the protocol of deep-level defect engineering in the technology of amorphous-aluminum-oxide-passivated Hall effect sensors and introduce a mature sensory platform with record-linear current-mode sensitivity of approximately 80 V/AT with -0.03-%/K stability in a broad temperature range between 300 K and 770 K, and likely far beyond 770 K.

Deep and shallow level defect passivation via fluoromethyl phosphonate for high performance air-processed perovskite solar cells

Air-processed perovskite solar cells (PSCs) with high performance are considered to be the inevitable trend of low-cost commercial manufacturing. Nevertheless, the deep- and shallow-level defects of humid-air-processed perovskite films are the main sources of photoelectric conversion efficiency (PCE) deficit. Herein, a difluoromethyl phosphonic acid diethyl ester (2F-PAE) with tri-chelation sites is implanted into perovskite absorber to passivate uncoordinated Pb2+/Pb clusters and raise formation energies of vacancies in perovskite films. The P = O/C-O groups in 2F-PAE offer tri-chelation sites to bind tightly with uncoordinated Pb2+/Pb clusters, which passivates deep-level defects and regulates perovskite crystallization. -CF2 groups in 2F-PAE generate electrostatic interaction with FA+, which helps to passivate shallow-level defects. The formation energies of Pb, I and FA vacancies can be increased by more than twice under the synergistic passivation of P = O, C-O and -CF2. Thus, the open-circuit voltage (VOC) of the humid-air-processed PSCs with 2F-PAE increases to 1.188 V. 2F-PAE passivated PSCs dramatically improve the PCE from 20.54 % to 23.69 %. PSCs using 2F-PAE display excellent moisture and thermal stability, retaining 82 % of its initial efficiency after 1500 h under continuous illumination, while the control PSCs maintain only 44 %. This strategy offers crucial insights for selecting multifunctional molecules to boost the performance of PSCs.

Self-assembled monolayers as hole transport layers for efficient thermally evaporated blue perovskite light-emitting diodes

Perovskite light-emitting diodes (PeLEDs) based on thermal evaporation technique have demonstrated great potential in newly-developed wide color gamut display applications. However, it is still a challenging task to obtain high efficiency thermally evaporated blue PeLEDs. One of the key issues is the lack of desirable functional materials with both hole transport function and perovskite buried interface modification function, which can alleviate the accumulation of high density of deep-level defects between hole transport layer (HTL) and perovskite emitting layer (EML) and weaken the interfacial nonradiative recombination process. In this study, we developed a new multifunctional wide-bandgap self-assembled monolayers (SAMs) suitable for thermally evaporated blue PeLEDs, named (2-(3-bromo-6-(4-formylphenyl)-9H-carbazol-9-yl)ethyl)phosphonic acid (CZPC). The interactions between the carbonyl groups (C = O) contained in CZPC and uncoordinated Pb2+ are critical for improving crystallinity and suppressing nonradiative losses at the buried perovskite-hole transporter interface. In addition, the phosphonic acid groups bonding with indium tin oxide (ITO) can form a self-assembled monolayer to facilitate carrier injection and transport. Finally, simplified thermally evaporated sky-blue (488 nm) PeLEDs utilize CZPC as HTL and no additional functional layers such as hole injection layer are used show excellent device performance with a maximum external quantum efficiency (EQE) of 5.42 %, accompanied by the CIE color coordinates of (0.07, 0.25) and a full width at half maximum (FWHM) of 24 nm. This work lays a foundation for the further exploration of SAMs on high-performance thermally evaporated blue PeLEDs towards ultra-high resolution display applications.

High external quantum efficiency monolayer MoS2(1−x)Se2x phototransistor with alloying-induced near-infrared absorption

Due to intriguing electrical and optical properties, two-dimensional MoS2 has gained significant attention and emerged as a promising material in photonic and optoelectronic fields. Nevertheless, the intrinsic optical absorption of monolayer MoS2 is limited in the visible region only, restricting applications toward near-infrared (NIR) photodetection. Herein, we engineered the optical properties of MoS2 via alloying with Se to extend its optical absorption to the NIR region, and the phototransistor was fabricated based on monolayer MoS2(1−x)Se2x (x = ∼0.1). When under 780 nm (∼1.59 eV) illumination, the device delivered a photoresponsivity of 75.38 A/W, a specific detectivity of ∼1012 Jones, and an external quantum efficiency up to 11 230%. Additionally, it was revealed by density functional theory calculations that NIR absorption originated from the transition of valence states of sulfur vacancy (Vs) interband energy states between +1 and 0, providing an interband energy level of 1.58 eV away from the conduction band minima. Moreover, alloying of Se can suppress deep-level defects formed via Vs, further boosting device performance. This work has demonstrated high-performance NIR phototransistors based on ternary monolayer MoS2(1−x)Se2x, providing both a viable solution and fundamental mechanisms for NIR-blind MoS2 with extended optical absorption.

Regulation of Anti‐Thermal Quenching and Emission Color in Eu2+‐Activated Na‐Beta‐Alumina Phosphors for Full‐Spectrum Illumination

AbstractBroadband cyan‐emitting phosphors are crucial to close the cyan gap of phosphor‐converted white light‐emitting diodes (pc‐WLEDs) for full‐spectrum illumination. In this work, efficient cyan‐emitting Eu2+‐activated phosphor is achieved through structural modulation, which exhibits anti‐thermal quenching behavior. Redshift from blue (469 nm) to cyan (500 nm) emission and enhancement of emission is achieved by codoping Mg2+ and Ge4+ into Eu2+‐activated Na‐beta‐alumina phosphor. The introduction of Mg2+ ions dominates the redshift, while Ge4+ dominates the enhancement of emission. Furthermore, the introduction of Mg2+ and Ge4+ reduces the content of deep trap levels related to VNa defect, which decreases the degree of anti‐thermal quenching and results in better thermal stability. The prototype pc‐WLED by using the cyan‐emitting phosphor exhibits higher color‐rendering index and potential to close the cyan gap of pc‐WLEDs for full‐spectrum illumination. This work presents a paradigm for exploring phosphors with highly efficient and thermally stable emissions.

Effect of proton irradiation induced localized defect clusters on recovery time and leakage current in silicon photoconductive semiconductor switches

Pulse recovery time in semiconducting devices depends strongly on minority carrier lifetime, bandgap-type-dependent recombination, impurity concentration, and subband placement. In indirect bandgap solids, such as silicon, it is dominated by Shockley–Reed–Hall (SRH) recombination via trap-based recombination centers yielding slow recombination. The sluggish recombination then limits the pulse repetition rate and consequently the average power to a load. For decades, fabrication and irradiation techniques, such as Au- and Pt-diffusion, and energized electron-, proton-, and alpha particle-beam bombardment have been used to adjust minority carrier lifetime in silicon. These techniques generate shallow- and/or deep-level lattice defects to promote/retard trap-assisted SRH recombination. Despite investigating the characteristics of the generated defects on target material, the prior-art falls short in comprehensively addressing their effects on device-level architecture, specifically photoconductive switching devices. In this work, the effect of proton irradiation-induced localized crystal defect clusters on minority carrier lifetime in silicon photoconductive semiconductor switches is investigated when bombarded with 2.5–5 MeV beam energies with fluences between 9 × 1012–11 × 1013 cm−2 at room temperature. Photo-illuminated recovery characteristics for proton-beam (p-beam) irradiated device models with three distinct defect profiles have been studied using Silvaco TCAD and results have been compared with the electron-beam (e-beam) irradiation model with three different distinct defect profiles. At 30× lower defect density, recovery time trends in the p-beam irradiated device model were seen to be on the same order of magnitude as the e-beam irradiated model. At similar defect densities (1 × 1016 cm−3), the profile with a uniformly distributed bulk defect profile performed 10× better from a recovery time viewpoint compared with the e-beam irradiation. Furthermore, three orders of magnitude reduction in leakage currents were noticed in p-beam irradiated models.

Epitaxial growth strategy for construction of Tm3+ doped and [hk1] oriented Sb2S3 nanorods S-scheme heterojunction with enhanced photoelectrochemical performance

With the advantages of high absorption coefficient, non-toxicity and low cost, Sb2S3 shows great potential as a narrow bandgap photocathode in the field of PEC hydrogen production. However, the separation and transportation of photogenerated carriers in the reported Sb2S3 photocathode are inefficient due to its anisotropy and the Fermi level being pinned by deep-level defects. Therefore, Tm3+ doped Sb2S3 nanorods with the selective carrier transport orientation were epitaxially grown on SnSe2 film by a simple hydrothermal strategy to modulate the defect property of Sb2S3, optimize carrier transportation and separation efficiency, and improve the PEC performance of photoelectrodes. Experimental results showed that the doping of Tm3+ weakening the Fermi level pinning while achieving the conversion of Sb2S3 to n-type conducting property. The S-scheme heterojunction formed by Tm3+ doped Sb2S3 nanorods labeled as Sb2S3: Tm3+ and SnSe2 nanosheets provided a stronger driving force to optimize carrier interface transportation. The photocurrent density (−0.91 mA cm−2) is increased about 18 times compared to the pristine Sb2S3 photocathode. This work developed an effective doping strategy to weaken the Fermi level pinning and provided a novel idea for the epitaxial growth of Sb2S3 nanorods to optimize the carrier transportation.