Shallow Defect Levels Research Articles

Tailoring Multifunctional Amine Salts Based on Anisole Liquid Soaking for Fabricating Efficient and Stable Perovskite Solar Cells.

The post-treatment based on spin-coating (SC) organic amine salts is commonly used for surface modification of perovskite films to eliminate defects. However, there is still a lack of systematic study and a unified understanding of the functions and mechanisms of different organic amine salts. The SC method is also not conducive to the industrialization of solar cells. In this work, we study three different organic amine salts, and a passivation strategy for perovskite films based on green anisole liquid soaking (ALS) has been developed. Phenylethylammonium iodide (PEAI), diethylamine hydroiodide (DEAI), and guanidine hydroiodide (GAI) organic amine salt passivators are selected to modify perovskite films, and their effect and working mechanism are also systematically estimated. It is found that PEAI passivates shallow-level defects on the surface of perovskite films, while DEAI incorporates into the perovskite lattice to suppress point defects, and GAI eliminates excess PbI2 residuals in perovskite films. These three organic-amine-salt-modified devices achieve enhanced power conversion efficiencies (PCE) of 21.82% (PEAI-ALS), 21.74% (DEAI-ALS), and 22.21% (GAI-ALS), which is much higher than that of the pristine device without treatment (19.95%). The PCE of the PEAI-ALS device retains nearly 94% of the initial efficiency after 1200 h in unpackaged conditions and about 40% ambient humidity, achieving the best stability performance. Particularly, the PEAI-ALS device has the best comprehensive performance in efficiency and stability. And PEAI is estimated by the SC method and ALS method, and it is found that the PEAI-ALS device achieves a higher PCE compared to the PEAI-SC device (21.51%). We believe that the post-treatment based on a combination of appropriate amine salts and ALS enables a universal approach for fabrication of perovskite solar cells with enhanced photovoltaic performance.

Selection of dopants and doping sites in semiconductors: the case of AlN

The choices of proper dopants and doping sites significantly influence the doping efficiency. In this work, using doping in AlN as an example, we discuss how to choose dopants and doping sites in semiconductors to create shallow defect levels. By comparing the defect properties of CN, ON, MgAl, and SiAl in AlN and analyzing the pros and cons of different doping approaches from the aspects of size mismatch between dopant and host elements, electronegativity difference and perturbation to the band edge states after the substitution, we propose that MgAl and SiAl should be the best dopants and doping sites for p-type and n-type doping, respectively. Further first-principles calculations verify our predictions as these defects present lower formation energies and shallower defect levels. The defect charge distributions also show that the band edge states, which mainly consist of N- s and p orbitals, are less perturbed when Al is substituted, therefore, the derived defect states turn out to be delocalized, opposite to the situation when N is substituted. This approach of analyzing the band structure of the host material and choosing dopants and doping sites to minimize the perturbation on the host band structure is general and can provide reliable estimations for finding shallow defect levels in semiconductors.

Heterogeneous Nucleation Regulation Amends Unfavorable Crystallization Orientation and Defect Features of Antimony Selenosulfide Film for High-Efficient Planar Solar Cells.

Antimony selenosulfide (Sb2(S,Se)3) has obtained widespread concern for photovoltaic applications as a light absorber due to superior photoelectric features. Accordingly, various deposition technologies have been developed in recent years, especially hydrothermal deposition method, which has achieved a great success. However, device performances are limited with severe carrier recombination, relating to the quality of absorber and interfaces. Herein, bulk and interface defects are simultaneously suppressed by regulating heterogeneous nucleation kinetics with barium dibromide (BaBr2) introduction. In details, the Br adsorbs and dopes on the polar planes of cadmium sulfide (CdS) buffer layer, promoting the exposure of nonpolar planes of CdS, which facilitates the favorable growth of [hk1]-Sb2(S,Se)3 films possessing superior crystallinity and small interface defects. Additionally, the Se/S ratio is increased due to the replacement of Se by Br, causing a downshift of the Fermi levels with a benign band alignment and a shallow-level defect. Moreover, Ba2+ is located at grain boundaries by coordination with S and Se ions, passivating grain boundary defects. Consequently, the efficiency is increased from 7.70 % to 10.12 %. This work opens an avenue towards regulating the heterogeneous nucleation kinetics of Sb2(S,Se)3 film deposited via hydrothermal deposition approach to optimize its crystalline orientation and defect features.

Roles of shallow energy level defect states on amplified spontaneous emission enhancement of CH3NH3PbBr3 perovskite crystals

Abstract In this work, we demonstrated the role of shallow energy level defect states on the emission of CH3NH3PbBr3 perovskite polycrystals under laser excitation. The perovskite polycrystals were synthesized by a simple, one-step, low-cost solution self-assembled method. By adjusting the sample preparation temperature from 303 to 373 K, we could manipulate the number of shallow energy level defect states, which were evaluated through low-temperature photoluminescence measurement. This led to an evolution of the CH3NH3PbBr3 perovskite polycrystals’ emission from amplified spontaneous emission to random lasing emission. As a result, the most efficient lasing threshold of 4 μJ mm−2 was achieved with the CH3NH3PbBr3 perovskite polycrystals synthesized at the optimum temperature of 333 K. Furthermore, the surface morphologies and the crystal structure of the CH3NH3PbBr3 perovskite polycrystals were also taken into consideration to unravel the role of defects in the CH3NH3PbBr3 perovskite polycrystals.

An ab-initio investigation of Sc and Y doped chalcopyrite MgGeN[formula omitted]

The doping of Scandium and Yttrium within chalcopyrite MgGeN2 were computationally investigated using density function theory (DFT) calculations. By calculating the formation energy, it was shown that independent single Sc and Y dopants energetically favor the occupation of the Mg site, inducing a shallow level within the conduction band. However, in the presence of a substitutional defect, the second dopant will occupy the neighboring Ge site. There is strong attractive interaction between two dopants, so that they are easily combined into a composite defect. In this case a shallow defect level appears above the valence band edge. Similar behavior is observed for the composite defects containing one dopant and an intrinsic cation vacancy, while those with one dopant and a nitrogen vacancy induce a deep defect level and greatly reduce the band gap. The investigation deepens the knowledge of Sc and Y doped II-IV-V2 compounds and may hence lead to more implementations.

Perovskite versus Standard Photodetectors.

Perovskites have been largely implemented into optoelectronics as they provide several advantages such as long carrier diffusion length, high absorption coefficient, high carrier mobility, shallow defect levels and finally, high crystal quality. The brisk technological development of perovskite devices is connected to their relative simplicity, high-efficiency processing and low production cost. Significant improvement has been made in the detection performance and the photodetectors' design, especially operating in the visible (VIS) and near-infrared (NIR) regions. This paper attempts to determine the importance of those devices in the broad group of standard VIS and NIR detectors. The paper evaluates the most important parameters of perovskite detectors, including current responsivity (R), detectivity (D*) and response time (τ), compared to the standard photodiodes (PDs) available on the commercial market. The conclusions presented in this work are based on an analysis of the reported data in the vast pieces of literature. A large discrepancy is observed in the demonstrated R and D*, which may be due to two reasons: immature device technology and erroneous D* estimates. The published performance at room temperature is even higher than that reported for typical detectors. The utmost D* for perovskite detectors is three to four orders of magnitude higher than commercially available VIS PDs. Some papers report a D* close to the physical limit defined by signal fluctuations and background radiation. However, it is likely that this performance is overestimated. Finally, the paper concludes with an attempt to determine the progress of perovskite optoelectronic devices in the future.

UV-random lasing of ZnO films decorated with Au nanoparticles and modification of lasing threshold by surface plasmon effect

Threshold energy values for random lasing action are determined from spectral and temporal coherence studies in systems with incoherent feedback. Zinc oxide films with and without their surface having been decorated with gold nanoparticles stand simultaneously for the active and the scattering medium, whereas pumping is carried out by a conventional laser system operating at the picosecond pulse regime. The influence of the gold surface on both the threshold and the intensity of the optical response is investigated. Whenever localized surface plasmon resonances are supported, electron mobility at the gold boundaries facilitates reinsertion of the trapped electrons into shallow defect levels to the conduction band. In consequence the characteristic visible emission from ZnO (green) due to transitions from such levels is suppressed, thus lowering the pumping threshold prerequisite for random lasing emission. The tunning of the random lasing threshold is achievable by means of control on the morphology and size effects of the gold nanoparticles. This contribution shows that specific post-thermal treatments could be exploited to adjust the lasing properties of novel metal decorated systems, which already feature random lasing before decoration. In principle, the extension of the decoration should be rather small to minimize response losses due to screening side effects of the metal phase, which obtrudes direct contact of the pumping photons with the semiconductor system.

Performance analysis of perovskite solar cell in presence and absence of defects

Studies of the effect of defects in any solar cell are important in achieving a satisfactory level of its performance. A comparative study with a defect-free against the defect-induced cell carries instant and ready information on laboratory/industry-based fabricated cell performance, which is prone to unavoidably induced defects. In spite of good deal of works on defects of cells such a study in an organized and comparative way remains absent to the knowledge of the authors. Ready and classified presentation of such a study, therefore, is considered to be significant. Present work is a result of motivation to fulfil this gap. This article presents a study of the effects of bulk and interface defects in perovskite solar cells. On examining the effects of deep and shallow defect levels on key performance metrics such as open-circuit voltage, short-circuit current density, and fill factor, the resulting study discusses an analysis of the impact of the defects on cell efficiency. A defect-free cell with optimal perovskite, hole-transport layer (HTL), and electron-transport layer (ETL) dimensions are analysed simultaneously to assess the level at which the defects can degrade the performance of a defect-free cell. It is observed that the defects, particularly in the deep levels, significantly impair the performance of a cell, including the open circuit voltage, short circuit current density, fill factor, and efficiency, compared to those in shallow levels.

Mitigation of Parasitic and Drift Capacitance-Induced Nonlinear Current Responses for Stable and Sensitive Perovskite X-ray Detectors.

The development of perovskite direct X-ray detectors shows potential for advancing medical imaging and industrial inspection precision. To ensure the optimal energy conversion efficiency of X-rays for reducing radiation doses, it is necessary for perovskites with thicknesses reaching hundreds of micrometers or even several millimeters to be utilized. However, the nonlinear current response becomes uncertain with such high thicknesses. For instance, the prevailing theory regarding the rapid trapping and release of charges by shallow-level defects falls short in explaining the nonlinear current response observed in high-quality single-crystal samples. Moreover, a significant nonlinear current response can degrade the detection performance. Here, we elucidate peculiar parasitic and drift capacitance-induced nonlinear current responses in perovskites, which arise from bulk structural deficiencies and interface junction width variation in addition to shallow-level defects. Both theoretical analysis and experimental findings demonstrate the effective suppression of nonlinear current responses by establishing bulk heterojunctions and refining interface junctions. Consequently, we have successfully developed highly linear current-responsive detectors based on polycrystalline MAPbI3 thick films. Notably, these detectors achieve a record sensitivity of 2.3 × 104 μC·Gyair-1·cm-2 under 100 kVp X-ray irradiation with a low bias of 0.1 V/μm, enabling enduring and high-resolution X-ray imaging for high-density objects. Successful fabrication and testing of a 64 × 64-pixel flat-panel prototype detector affirm the widespread applicability of these strategies in rectifying nonlinear current responses in perovskite-based X-ray detectors.

Shallow-level defect passivation by 6H perovskite polytype for highly efficient and stable perovskite solar cells

The power conversion efficiency of perovskite solar cells continues to increase. However, defects in perovskite materials are detrimental to their carrier dynamics and structural stability, ultimately limiting the photovoltaic characteristics and stability of perovskite solar cells. Herein, we report that 6H polytype perovskite effectively engineers defects at the interface with cubic polytype FAPbI3, which facilitates radiative recombination and improves the stability of the polycrystalline film. We particularly show the detrimental effects of shallow-level defect that originates from the formation of the most dominant iodide vacancy (VI+) in FAPbI3. Furthermore, additional surface passivation on top of the hetero-polytypic perovskite film results in an ultra-long carrier lifetime exceeding 18 μs, affords power conversion efficiencies of 24.13% for perovskite solar cells, 21.92% (certified power conversion efficiency: 21.44%) for a module, and long-term stability. The hetero-polytypic perovskite configuration may be considered as close to the ideal polycrystalline structure in terms of charge carrier dynamics and stability.

Enhancing efficiency and stability of inverted perovskite solar cells through synergistic suppression of multiple defects via poly(ionic liquid)-buried interface modification

The stability of perovskite solar cells (PSCs) is adversely affected by nonradiative recombination resulting from buried interface defects. Herein, we synthesize a polyionic liquid, poly(p-vinylbenzyl trimethylammonium hexafluorophosphate) (PTA), and introduce it into the buried interface of PSCs. The quaternary ammonium cation (N(–CH3)3+) in PTA can fill the vacancies of organic cations within the perovskite structure and reduce shallow energy level defects. Additionally, the hexafluorophosphate (PF6−) in PTA forms a Lewis acid-base interaction with Pb2+ in the perovskite layer, effectively passivating deep energy level defects. Furthermore, hydrogen bonding can be established between organic cations and the PF6− anion, preventing the formation of shallow energy level defects. Through this synergistic mechanism, the deep and shallow energy level defects are effectively mitigated, resulting in improved device performance. As a result, the resulting treated inverted PSC exhibits an impressive power conversion efficiency (PCE) of 24.72 %. Notably, the PTA-treated PSCs exhibit remarkable stability, with 88.5 % of the original PCE retained after undergoing heat aging at 85 °C for 1078 h, and 89.1 % of the initial PCE maintained following continuous exposure to light for 1100 h at the maximum power point. Synergistically suppressing multiple defects at the buried interface through the use of polyionic liquids is a promising way to improve the commercial viability of PSCs.

Donor-induced electrically charged defect levels: examining the role of indium and n-type defect-complexes in germanium

Defect levels induced by defect-complexes in Ge play important roles in device fabrication, characterization, and processing. However, only a few defect levels induced by defect-complexes have been studied, hence limiting the knowledge of how to control the activities of numerous unknown defect-complexes in Ge. In this study, hybrid density functional theory calculations of defect-complexes involving oversize atom (indium) and n-type impurity atoms in Ge were performed. The formation energies, defect-complex stability, and electrical characteristics of induced defect levels in Ge were predicted. Under equilibrium conditions, the formation energy of the defect-complexes was predicted to be within the range of 5.90–11.38 eV. The defect-complexes formed by P and In atoms are the most stable defects with binding energy in the range of 3.31-3.33 eV. Defect levels acting as donors were induced in the band gap of the host Ge. Additionally, while shallow defect levels close to the conduction band were strongly induced by the interactions of Sb, P, and As interstitials with dopant (In), the double donors resulting from the interactions between P, As, N, and the host atoms including In atom are deep, leading to recombination centers. The results of this study could be applicable in device characterization, where the interaction of In atom and n-type impurities in Ge is essential. This report is important as it provides a theoretical understanding of the formation and control of donor-related defect-complexes in Ge.

Engineering shallow and deep level defects in κ-Ga2O3 thin films: comparing metal-organic vapour phase epitaxy to molecular beam epitaxy and the effect of annealing treatments

Orthorhombic gallium oxide (κ-Ga2O3) is an ultra-wide bandgap semiconductor with great potential in new generation electronics. Its application is hindered at present by the limited physical understanding of the relationship between synthesis and functional properties. This work discusses the effects of growth method (metal-organic vapour phase epitaxy and molecular beam epitaxy) as well as annealing treatments in different atmospheres (O2, H2) on point defects in κ-Ga2O3 layers epitaxially grown on c-plane sapphire. Comprehensive experimental characterization by X-ray diffraction, photo current-as well as photoluminescence excitation spectroscopy, and X-ray photo electron spectroscopy is combined with first principles calculations of the point defects’ formation and complex-dissociation energies. We demonstrate that for κ-Ga2O3 the concentration of shallow and deep level defects can be sensitively controlled through annealing treatments at temperatures (T = 500 °C) well below the thermal stability threshold of this polymorph. In particular, our results suggest that hydrogen-related defects (e.g., H-interstitials, Ga-vacancies—H complexes) play a key role in this process. While we provide direct exemplary implications of our results for the performances of κ-Ga2O3 based photodetectors, these findings are predicted to impact further application fields of κ-Ga2O3, such as high electron mobility transistors or memory devices.

Deciphering interfacial properties and intermediaries via probing lattice deformations: Growth solution chemistry for mixed/pure phase metal oxide/perovskites

pH of the growth solution of nanomaterials has been employed as a controlling agent in the morphology and synthesis of various metal oxides. The key points in the reconciliation with the thus formed nanostructures inevitably revolve around the impact of H+ and OH- ions on the oxide phases formed during various stages of the phase evolution. Here, a careful elucidation of acidic and alkaline conditions that influence the evolution of the perovskite of Strontium titanate (STO) has been done taking care to avoid the influence of other reagents by avoiding their use altogether. Multiple incremental steps of the growth solution’s pH were the only variable, allowing a direct correlation of the alkalinity with the several interesting materializations of the perovskite composition. The fundamental aspects on the development of the different phases such as the lattice strains due to expansions and contractions of the lattice, integration of shallow level defects as a result of the growth conditions, visualizations of the interfaces between multiple phases which were always present when the growth conditions were not completely alkaline have been revealed through different structural and morphological characterizations. The catalytic property of the samples prepared at different pH levels investigated using UV light exhibited markedly different photocatalytic activity toward Rhodamine B (RhB). We propose that the tuned phase compositions and morphologies are the reason for the observed variations. The different compositions of intermediaries are interesting candidates for different applications that are concerned with defect and interface engineering, and the data presented herewith reveal precise conditions for achieving each of these interesting compositions as well as realizing pristine STO without the typical presence of secondary phases such as carbonates.

A Comprehensive Review on Mechanisms and Applications of Rare‐Earth Based Perovskite Nanocrystals†

Comprehensive SummaryRare earth (RE) ions, with abundant 4f energy level and unique electronic arrangement, are considered as substitutes for Pb2+ in perovskite nanocrystals (PNCs), allowing for partial or complete replacement of lead and minimizing environmental impact. This review provides a comprehensive overview of the characteristics of RE‐doped PNCs, including up‐conversion luminescence, down‐conversion luminescence, and quantum confinement effects, etc. Additionally, RE doping has been found to effectively suppress defect formation, reduce nonradiative recombination, enhance photoluminescence quantum yield (PLQY), and even allow for controlling over the morphology of the nanocrystals. The review also highlights the recent advancements in lead‐free RE‐based perovskites, especially in the case of Eu‐based perovskites (CsEuBr3 and CsEuCl3). Furthermore, it briefly introduces the applications of PNCs in various fields, such as perovskite solar cells (PSCs), luminescent solar concentrators (LSCs), photodetectors (PDs), and light‐emitting diodes (LEDs). A systematic discussion on the luminescence mechanisms of RE‐doped PNCs and lead‐free RE‐based perovskites is provided, along with an outlook on future research directions. The ultimate goal of this review is to provide guidance for the development of RE‐based perovskite optoelectronic devices. Key ScientistsIn 2015, Kovalenko et al. pioneered the synthesis of lead‐based perovskite nanocrystals using the thermal injection method. Concurrently, Zhong et al. introduced the ligand‐assisted reprecipitation method. These methods have become the predominant approaches for fabricating lead‐based perovskite nanocrystals. In 2017, Song et al. successfully incorporated various rare earth ions (Ce3+, Sm3+, Eu3+, Tb3+, Dy3+, Er3+, and Yb3+) into CsPbCl3 perovskite nanocrystals. They also observed the quantum cutting effect induced by defect states, facilitated by the doping of Yb3+. Gamelin et al. subsequently proposed that CsPbCl3:Yb3+ nanocrystals exhibit quantum cutting effects due to the introduction of charge‐compensating defects (VPb), resulting in the formation of Yb3+‐VPb‐Yb3+ defect complexes with shallow defect levels. In 2020, Zhang et al. successfully doped Nd3+ into CsPbBr3, yielding blue luminescent nanocrystals with a central wavelength of 459 nm and up to 90% photo‐luminescence quantum yield (PLQY). In the same year, Yang et al. achieved the synthesis of pure phase CsEuCl3 perovskite nanocrystals for the first time. In 2022, Paik et al. synthesized Cs3LnCl6 (Ln = Y, Ce, Gd, Er, Tm, Yb, Eu, Tb) nanocrystals using the thermal injection method. In 2023, Zhang et al. successfully introduced Ni2+ doping into CsEuCl3, enhancing the PLQY of CsEuCl3 nanocrystals from 5% to 19.7%. This review focuses on the development history of perovskite nanocrystals, including rare earth‐doped lead‐based perovskite nanocrystals and rare earth‐based lead‐free perovskite nanocrystals, as well as their applications.

Numerical modeling of defects induced dark current in halide perovskite X-ray detectors

Metal halide perovskites have been widely used in x-ray detection due to their outstanding optoelectronic properties. However, the dark current of perovskite x-ray detectors is not appreciably low for integration on thin-film transistors pixel circuits and thus limits their applications in X-ray imaging. Based on numerical models, we investigate the correlation between the dark current and defects of perovskite x-ray detectors. The deep-level defects are the major factor to induce dark current, which has a proportional relation to the defect density. Compared to deep-level defects, the dark current induced by shallow-level defects depends on both of defect energy level and defect density. At last, simulation results present a guidance to engineer defects with suitable values of density and energy level, which yields desirably low dark current. This work provides implications and theoretical guidance for the optimization of defects in halide perovskites, which is believed to assist the further development of x-ray detectors with a low dark current density.

How do the oxygen vacancies affect the photoexcited carriers dynamics in β-Ga2O3？

β-Ga2O3 is a rising star material for solar-blind photoelectronic detectors (PDs) since its excellent properties and lower cost than GaN and SiC. However, the high density of O vacancy (VO) strongly affect the performance of devices. In this work, we investigate the effect of VOs on carrier dynamics in β-Ga2O3 and its meaningful application in solar-blind PDs by the time-dependent density functional theory (TDDFT) and nonadiabatic molecular dynamics (NAMD). We find the three inequivalent VOs (VO1, VO2, and VO3) play different roles in carrier dynamics although they all introduce deep defect states in the bandgap, which significantly shorten the lifetime (τ) of carriers. VO1 and VO3 form nonradiative recombination centers, considerably decreasing the τ from 23.10 ns to 0.12 ns and 0.11 ns, respectively. VO2 forms shallow-level defects, and the τ is 0.47 ns, which weakens the decline of the carrier compared to VO1 and VO3. Our findings provide a different angle to understand the disputation on relationship between point defects and device performance based on β-Ga2O3, and to further improve the device performance by defect engineering.

Enhanced Charging/Discharging Process in Perovskite Active Light Source for High‐Speed Visible‐Light Communication

AbstractMetal halide perovskites are promising light source materials for visible light communication (VLC) due to their excellent photoelectric properties and small resistance‐capacitance time constant. However, previous reports mainly used perovskites as the passive light sources, which not only makes it susceptible to posterior excitation light sources, but also complex in the integration process. Herein, the quasi‐2D PEA2Csn‐1PbnBr3n+1 perovskite light–emitting diodes (PeLEDs) as an active light source in VLC link is demonstrated. It is found that the charging/discharging process of PeLEDs is an important factor governing the ‐3 dB bandwidth (f‐3 dB) of the VLC. To improve this, 3‐sulfopropyl methacrylate potassium salt (SMPS) molecules are introduced into perovskite to simultaneously passivate deep and shallow energy level defects at grain boundaries. Additionally, the multiple quantum wells structures of PEA2Csn‐1PbnBr3n+1 are modified to be flat. At the optimal SMPS concentration, the maximum external quantum efficiency of PeLEDs reaches 21.5%. Meanwhile, the VLC achieves 3.2 MHz f‐3 dB with data transmission of 18.6 Mbps, which is the highest f‐3 dB in PeLEDs with the same active area. Hence, it provides a versatile method to improve the performance of VLC links based on active light sources and advances toward the goal of high‐speed, energy‐efficient and secure free communication.

Minimizing interfacial energy losses in inverted perovskite solar cells by a dipolar stereochemical 2D perovskite interface

Inverted perovskite solar cells (PSCs) have attracted broad research and industrial interest owing to their suppressed hysteresis, cost-effectiveness, and easy-fabrication. However, the issue of non-radiative recombination losses at the n-type interface between the perovskite and fullerene has impeded further improvement of photovoltaic performance. Here, we modify the n-type interface of FAPbI3 perovskite films by constructing a stereochemical two-dimensional (2D) perovskite interlayer, in which the organic cations comprise both pyridine and ammonium groups. The pyridine N donor can create stable bonding with the surface-uncoordinated Pb on the perovskite, thereby passivating the shallow-level defects and enhancing the air stability of the film. Furthermore, the pyridine N donor also offers a positive polar interface to decrease the surface work function of the perovskite film, enabling n-type modification. Ultimately, we employ a p-i-n photovoltaic (PV) device with the positive dipole interlayer at perovskite/fullerene contact and achieve remarkable photoelectric conversion efficiency (PCE) of 22.0%.

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.