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Smartphones are usually packed with a large number of features. An increasing number of researchers are paying attention to the technological capabilities of smartphones, which is a new topic and research interest. This paper proposes a method using smartphones and digital photogrammetry to measure the discontinuity orientation of a rock mass. Smartphone photos satisfying a certain overlap rate provide an efficient method for generating point cloud models of rock outcrops based on image matching. Using the target and the generated point cloud model allows for determining actual geographic coordinates and the measurement of discontinuity orientations. The method proposed has been applied to two different study areas. The discontinuity orientations measured by the proposed method are compared with those measured by the manual method in two cases. The results show a good agreement, verifying the reliability and accuracy of the proposed method. The main contribution of this paper is to use knowledge of coordinate rotation to determine the actual geographic location of the model through a square target. The equipment used in this study is simple, and photogrammetric field surveys are easy to carry out.

The thermoelectric performance of n-type Bi2Te3needs further enhancement to match that of its p-type Bi2Te3counterpart and should be considered for competitive applications. Combining Cu/Cl and multiscale additives (AgBiSe2) presents a suitable route for such enhancement. This is evidence of the enhanced thermoelectric performance of Bi1.995Cu0.005Te2.69Se0.33Cl0.03. Moreover, by incorporating 0.65 wt % AgBiSe2(ABS) into Bi1.995Cu0.005Te2.69Se0.33Cl0.03, we further reduce its lattice thermal conductivity to ∼0.28 W m–1K–1at 353 K owing to the extra phonon scattering of multiscale ABS. Additionally, the Seebeck coefficient enhances (−183.89 μV K–1at 353 K) owing to the matrix’s reduced carrier concentration caused by ABS. As a result, we achieve a high ZTof ∼1.25 (at 353 K) and a high ZTaveof ∼1.12 at 300–433 K for Bi1.995Cu0.005Te2.69Se0.33Cl0.03+ 0.65 wt % ABS. This work provides a promising strategy for enhancing the thermoelectric performance of n-type Bi2Te3through Cu/Cl doping and ABS incorporation.

Functional groups in cellulose acetate butyrate interact with anions and cations in perovskite to significantly improve device stability by inhibiting the decomposition of perovskite.

Bismuth telluride-based (Bi2Te3) alloys have long been considered the best thermoelectric (TE) materials at room temperature. However, the n-type Bi2Te3alloys always exhibit poor thermoelectric performance than their p-type counterpart, which severely limits the energy conversion efficiency of thermoelectric devices. Here, we demonstrate that incorporating AgBiSe2can concurrently regulate the electrical and thermal transport properties as well as improve the mechanical performance of n-type Bi2Te2.69Se0.33Cl0.03for high thermoelectric performance. Among these, AgBiSe2effectively enhanced the Seebeck coefficients of n-type Bi2Te2.69Se0.33Cl0.03due to the reduced carrier concentration and reduced the thermal conductivity of n-type Bi2Te2.69Se0.33Cl0.03owing to the enhanced phonon scattering by AgBiSe2as well as its low thermal conductivity nature. Consequently, the simultaneous optimization of electrical and thermal transport properties enables us to achieve a maximum ZTof ∼1.21 (at ∼353 K) and an average ZTaveof ∼1.07 (300–433 K) for 3.5 wt % AgBiSe2-incorporated Bi2Te2.69Se0.33Cl0.03, which are ∼25.62 and ∼23.36% larger than those of Bi2Te2.69Se0.33Cl0.03, respectively. This work proves that the incorporation of AgBiSe2is an efficient way to improve the thermoelectric performance of bismuth telluride-based materials.

The non-radiative recombination loss caused by diverse defects within SnO2electron transport layer (ETL), perovskite film, and their interface greatly hinders the further improvement of the performance and stability of flexible perovskite solar cells (PSCs). Therefore, it is urgent to develop an effective strategy to address these issues. Herein, a multifunctional material, phospho-ethanolamine (PE), is introduced into SnO2aqueous colloids to suppress defects and prepare high-quality ETL. The results demonstrate that the incorporation of PE can significantly reduce the number of Sn dangling bonds due to the formation of new Sn—O—P bonds, which is beneficial to ameliorating the electrical properties of SnO2and obtaining dense SnO2film. Meanwhile, the amino group (NH2) of PE can interact with uncoordinated Pb2+in perovskite, thereby suppressing SnO2/perovskite interface defects and obtaining improved perovskite film quality. Consequently, the optimized flexible and rigid PSCs based on the SnO2-PE composite ETL yield outstanding photoelectric conversion efficiency (PCE) of 18.48% and 21.61%, respectively. Moreover, flexible PSCs based on SnO2-PE present excellent mechanical durability, and 90.6% of the original PCE is retained after 1000 bending cycles.

An increasing number of studies have reported producing composite structures by combining thermoelectric and functional materials. However, combining energy filtering and ferroelectric polarization to enhance the dimensionless figure of merit thermoelectric ZTremains elusive. Here we report a composite that contains nanostructured BaTiO3embedded in a Bi0.5Sb1.5Te3matrix. We show that ferroelectric BaTiO3particles are evenly composited with Bi0.5Sb1.5Te3grains reducing the concentration of free charge carriers with increasing BaTiO3content. Additionally, as a result of the energy-filtering effect and ferroelectric polarization, the Seebeck coefficient was improved by ∼10% with a ∼10% improvement in power factors. The BaTiO3phase can effectively scatters phonons reducing lattice thermal conductivity κl(0.5 W m–1K–1) and increasing ZTto 1.31 at 363 K in Bi0.5Sb1.5Te3composites with 2 vol % BaTiO3content giving an improvement of ∼25% over pure Bi0.5Sb1.5Te3. Our work indicates that the introduction of ferroelectric nanoparticles is an effective method for optimizing the ZTof Bi0.5Sb1.5Te3-based thermoelectric materials.

InSb is a narrow-bandgap semiconductor with a zinc blende structure and has been wildly applied in photodetectors, infrared thermal imaging, and Hall devices. The facts of decent band structure, ultrahigh electron mobility, and nontoxic nature indicate that InSb may be a potential mid-temperature thermoelectric material. The critical challenges of InSb, such as high thermal conductivity and small Seebeck coefficient, have induced its ultrahigh lattice thermal conductivity, and thus low ZTvalues. In view of this, we have developed a competitive strategy typified by the cost-efficient nanocompositing of zwt% QSe2(Q = Sn, W). Specifically, the QIn+and SeSb+point defects were introduced in the InSb system by nanocompositing the vested two-dimensional layered QSe2. In addition, the enlarged valence band maximum of intrinsic WSe2acted as ladders can scatter a fair number of hole carriers, resulting in the relatively enhanced Seebeck coefficient of high temperature. Moreover, the disorderly distributed nanosheets/particles, and dislocations acting as obstacles can effectively delay the heat flow diffusion, inducing the strong scattering of thermal phonons. Consequently, an enhanced power factor of ∼33.3 µW cm−1K−2and ZTvalue of ∼0.82 at 733 K have been achieved in the 3% WSe2sample, companied with the engineering output power density ωmax∼233 µW cm−2and thermoelectric conversion efficiency η∼5.2%. This artificially designed approach indicated by suited nanocompositing can integrate several engineering strategies such as point defects, nanoengineering, and energy filtering into one, providing a reference to optimize the thermoelectric performance of other thermoelectric systems.

The lead-free double perovskite has been proven to be one of the promising alternatives to solve the stability and toxicity problems of lead-based organic–inorganic hybrid perovskite solar cells. Here, high-quality Cs2AgBiBr6double perovskite films with large grains and smooth surface have been prepared through a sequential-vapor-deposition method, and a low-cost and eco-friendly Cu2O film with a suitable energy level and good electrical properties was prepared as an efficient hole transport layer by vacuum vapor deposition for the first time. The Cu2O-based devices achieve a champion power conversion efficiency increasing from 1.03 to 1.52% and an enhancement of photovoltage from 1.083 to 1.198 V compared with their organic counterparts. More importantly, the Cu2O-based devices have excellent stability; they maintained the initial 96% efficiency under environmental conditions after 33 days of unpackaged storage. These results also point out the direction for the further development of these new promising perovskite solar cells.

Exploiting materials with effective heat dissipation and electromagnetic shielding performance is highly desirable for high integration and high-power density electronic devices. Herein, we introduce a flexible carbon/ferroelectric/thermoelectric (i.e. C/FE/TE) hybrid film with layer-by-layered carbon, PZT/PVDF-TrFE, and bismuth telluride alloys (p-type Bi0.5Sb1.5Te3or n-type Bi2Te2.5Se0.5), it enables us to achieve thermoelectric cooling and electromagnetic shielding concurrently. More importantly, the electrical performance of the thermoelectric layer can be tuned by the polarization of the ferroelectric layer, and the maximum power factors of 12.7 μW/cmK2and 5.3 μW/cmK2are obtained for Bi0.5Sb1.5Te3and Bi2Te2.5Se0.5, respectively. Using these C/FE/TE hybrid films, we fabricated a radial-shaped flexible thermoelectric cooling device, which showed a net cooling temperature difference of 1.08 K at 300 K. In addition, the impedance mismatch between free space and C/FE/TE induces reflection loss, the bismuth telluride alloys and carbon layers cause conduction loss, while the polarized PZT/PVDF-TrFE, as well as the interfacial polarization between bismuth telluride alloys and PZT/PVDF-TrFE layers leads to polarization loss. Thus, a high electromagnetic shielding performance with a maximum average shielding efficiency of 32.0 dB in the frequency range of 8.2–12.4 GHz (i.e. X-band) was also achieved in the C/FE/TE hybrid film.

Transparent electro-optic (EO) oxide ceramics are known for their rapid EO effects. EO ceramics have several advantages over single-crystals, including variable size and shape, controllable chemical composition, superior mechanical properties, and low cost. Synthesis of high-performance transparent EO ceramics requires high purity of raw materials, high density, homogeneous composition, uniform grain size, and relatively wide bandgap. Powder synthesis and sintering are two of the critical steps involved in the fabrication of highly transparent EO ceramics. Using high-activity precursor powders has been effective in fabricating high-density ceramics that demonstrate excellent EO performance. The sintering process plays a crucial role in achieving this result, and currently, there are several sintering methods available for producing high-density ceramics, including hot-pressing, hot isostatic pressing, and spark plasma sintering. This review summarizes the recent progress in materials and processes used to develop transparent EO ceramics, including those based on lead zirconate titanate, lead magnesium niobate-lead titanate, and lead-free potassium sodium niobate. In addition, several novel applications of transparent EO ceramics, including light shutters, spectral filters, optical memory, as well as image storage and displays are reviewed. In the end, the review concludes with a discussion of future trends and perspectives.

Ferroelectric domain walls (DWs) are important nanoscale interfaces between two domains. It is widely accepted that ferroelectric domain walls work idly at terahertz (THz) frequencies, consequently discouraging efforts to engineer the domain walls to create new applications that utilize THz radiation. However, the present work clearly demonstrates the activity of domain walls at THz frequencies in a lead-free Aurivillius phase ferroelectric ceramic, Ca0.99Rb0.005Ce0.005Bi2Nb2O9, examined using THz-time-domain spectroscopy (THz-TDS). The dynamics of domain walls are different at kHz and THz frequencies. At low frequencies, domain walls work as a group to increase dielectric permittivity. At THz frequencies, the defective nature of domain walls serves to lower the overall dielectric permittivity. This is evidenced by higher dielectric permittivity in the THz band after poling, reflecting decreased domain wall density. An elastic vibrational model has also been used to verify that a single frustrated dipole in a domain wall represents a weaker contribution to the permittivity than its counterpart within a domain. The work represents a fundamental breakthrough in understanding the dielectric contributions of domain walls at THz frequencies. It also demonstrates that THz probing can be used to read domain wall dielectric switching.

Bi2(TeSe)3is a dominant n-type thermoelectric material used in commercial applications. However, its toxicity and rarity hamper further large-scale industrial applications. Herein, we develop a Ag8SiSe6-based composite as a promising n-type semiconductor with the advantages of nontoxicity and elemental abundance. Ag8SiSe6composites with Ag2Se and Si nanoprecipitation are fabricated by a unique precipitation reaction sensitive to the hot pressing process. The energy-filtering effect between these phases optimizes electrical resistivity (∼14.59 μΩ·m) and the Seebeck coefficient (above −150 μV·K–1) of the composites, resulting in a maximum power factor of ∼1772 μW·m–1·K–2(@125 °C), which is the highest value in an argyrodite system near room temperature. Nanoprecipitation of Ag2Se and Si can also scatter more phonons and further reduce the lattice thermal conductivity to 0.20 W·m–1·K–1. As a result, a maximum ZTvalue of ∼0.9 (@125 °C) and an average ZTvalue of ∼0.7 (25–200 °C) are obtained in the composite with 12 vol % Ag2Se and 0.23 vol % Si, which is sintered at 525 °C. These thermoelectric properties are comparable to those of a commercial n-type Bi2Te3compound. In addition, the Ag8SiSe6composite has robust mechanical properties (Vickers hardness of >110 HV and bending strength of 70.6 MPa), much better than those of other thermoelectric compounds, because of which Ag8SiSe6has great commercial application as an alternative to Bi2Te3-based compounds.

SnTe has attracted considerable attention as an environmentally friendly thermoelectric material. The thermoelectric figure of merit ZT value is related to low thermal conductivity that can be successfully realized using fabrication of nanostructures. However, the practical realization of SnTe nanostructured composites is often limited by long reaction time, low yield, and aggregation of nanoparticles. Herein, a simple substitution reaction between Cu2Se and SnTe was adopted to realize Cu1.75Te-SnTe nanocomposites with unique all-scale hierarchical structures. On the atomic level, the substitution SeTeis introduced into the lattice via the reaction between Cu2Se and SnTe; on the nanoscopic level, Cu1.75Te nanoinclusions with 10 nm size are evenly distributed at the grain boundaries of SnTe with average grain size less than 1 μm; on the mesoscopic level, these SnTe grains stack up to larger particles (10–20 μm), which are further surrounded by Cu1.75Te grains with a predominant size of 1–2 μm. These hierarchical structures, together with additional SnTe stacking faults, can effectively scatter phonons with different wavelengths to reduce the lattice thermal conductivity. At 873 K, a thermal conductivity value of 0.49 W·m–1·K–1was obtained in the SnTe nanocomposite sample with 0.057 Cu1.75Te molar content, which is 40% lower than that of the pristine SnTe. By using the same approach for scattering phonons across integrated length scales, a ZTvalue of 1.02 (∼80% enhancement, compared with that of the pristine SnTe) was achieved at 873 K for the sample of the SnTe nanocomposite with 0.034 Cu1.75Te molar content. This large increase in ZTvalues highlights the role of multiscale hierarchical architecture in controlling phonon scattering, offering a viable alternative to realize higher performance thermoelectric bulk materials.

ABSTRACTMgAgSb material has been attracting more attention for its non-toxicity and elemental abundance of raw materials. We herein utilise the microwave-assisted process and spark plasma sintering to fabricate MgAgSb samples. Different from the sample prepared by the melting process, there is an Ag3Sb second phase in the matrix of MgAgSb prepared by the microwave-assisted process. Ag3Sb obviously increases carrier concentration and leads to low electrical resistivity and high power factor. The maximum power factor is about 2000 μWm−1 K−2, which is double larger than that of MgAgSb sample prepared by the melting process. During the microwave-assisted process, many stacking faults and edge dislocations are introduced into the matrix which leads to the appearance of flake sub-grains with a thickness of 0.5–1 μm. These defects strengthen phonons’ scattering and reduce the lattice thermal conductivity. The decoupling of transport properties leads to 20% enhancement of ZT value (∼0.76@548 K), compared with the sample prepared by the melting process.

MgAgSb material has been attracting more attention for its non-toxicity and elemental abundance of raw materials. We herein utilise the microwave-assisted process and spark plasma sintering to fabricate MgAgSb samples. Different from the sample prepared by the melting process, there is an Ag3Sb second phase in the matrix of MgAgSb prepared by the microwave-assisted process. Ag3Sb obviously increases carrier concentration and leads to low electrical resistivity and high power factor. The maximum power factor is about 2000 µWm-1K-2, which is double larger than that of MgAgSb sample prepared by the melting process. During the microwave-assisted process, many stacking faults and edge dislocations are introduced into the matrix which leads to the appearance of flake sub-grains with a thickness of 0.5–1 µm. These defects strengthen phonons’ scattering and reduce the lattice thermal conductivity. The decoupling of transport properties leads to 20% enhancement of ZT value (~0.76@548 K), compared with the sample prepared by the melting process.

Numerical manifold method (NMM) is an effective method for simulating block system, however, significant errors are found in its simulation of rotation problems. Three kinds of errors, as volume expansion, stress vibration, and attenuation of angular velocity, were observed in the original NMM. The first two kind errors are owing to the small deformation assumption and the last one is due to the numerical damping. A large deformation NMM is proposed based on large deformation theory. In this method, the governing equation is derived using Green strain, the large deformation iteration and the open-close iteration are combined, and an updating strategy is proposed. The proposed method is used to analyze block rotation, beam bending, and rock falling problems and the results prove that all three kinds of errors are eliminated in this method.

In this work, a composite product of Mn-substituted SnTe, SnO2nanoparticles, and MnTe-supersaturated precipitates has been fabricated by a simple in situ reaction between SnTe and MnO2for the first time. Benefiting from the synergistic effect induced by the product of in situ reaction, a remarkable improvement in the thermoelectric performance has been achieved. On the one hand, Mn substitution in SnTe can effectively modify the band structure and enhance the electrical properties of SnTe; on the other hand, the thermal transport can also be dramatically suppressed by in situ reaction-derived multiscale phonon scattering by point defects, SnO2nanoparticles, and supersaturated MnTe precipitates. Ultimately, a maximum ZTof ∼1.5 at 873 K has been achieved in the SnTe + 10 mol % MnO2sample, which increases by 224% in comparison with the pristine SnTe, representing one of the best results ever reported for SnTe-based thermoelectric materials.

α-MgAgSb (α-MAS) has recently been discovered to be a promising p-type thermoelectric material owing to its earth-abundant and nontoxic nature. However, there are two main disadvantages hindered the large-scale application of α-MAS, one is the single α-MAS phase prepared by conventional method requires for an extended period of time, and the other is the severely bipolar effect thus poor electric properties. In this scenario, we have presented an effective approach typified by SnTe nanocompositing to significantly enhance the thermoelectric performance of the rapidly microwave-synthesized α-MAS system. Specifically, the pure α-MAS compound was first produced by using a rapidly microwave synthesis. After the initial preparation, high-quality SnTe nanoparticles fabricated by a facile solvothermal method were incorporated into the microwave-synthesized α-MAS matrix. It is deserve to be mentioned that the rapidly microwave synthesis purifies the single α-MAS phase and allows the preparative time to be diminished from over 2 weeks to as little as 5 days. Moreover, the severe bipolar effect of pristine α-MAS has been retarded effectively by the following step typified by compositing SnTe nanoinclusions, leading to a large Seebeck coefficient, thus significantly enhanced a power factor in α-MAS/SnTe-composited system. Concurrently, the lattice thermal conductivity has also been greatly reduced because of the extra phonon scattering because of the multiscale hierarchical architecture (e.g., SnTe nanostructures, high-density stacking faults, and elastic strain fields). Eventually, an enhanced figure of merit ZT of ∼1 at 548 K, which increases by ∼53% compared with pristine α-MAS, has been achieved in the 3 at % SnTe-composited sample. This work impels the potential application of the α-MAS thermoelectric material as a robust candidate for a waste heat recovery below 573 K.

Pb-free MnTe has recently been discovered to be a promising thermoelectric material because of its low toxicity and eco-friendly nature. Here, we have proposed and demonstrated an effective approach to boost the electrical transport of MnTe compound via reinforcing bond covalency through M/S (alkaline dopants M = Li, Na, and K) co-doping. By means of this strategy, the electrical conductivity was significantly improved owing to the increasing carrier concentration and mobility, which is attributed to the decreasing electronegativity difference |χTe− χM| as M going from K to Na to Li. The single Kane band model enables a reliable assessment of their temperature-dependent electrical properties, further suggesting that the bipolar effects at high temperature can be effectively suppressed by reinforcing bond covalency. Moreover, beneficial from alkali doping and sulfur substitution, the lattice thermal conductivities have been sharply reduced to amorphous limit through intensive phonon scattering induced by the multiscale hierarchical architecture such as the nanostructures, coherent grain boundary and high-density dislocations, etc. As a result, a record-high peak zT of ~1.3 @ 873 K, corresponding to a calculated engineering output power density ~1.46 Wcm2and leg efficiency η ~8.4%, has been achieved in the Li/S co-doped (Mn1.04Li0.02Te0.99S0.01) sample. This work provides a referential route to enhance electrical properties via synergistically improving carrier concentration and mobility by reinforcing bond covalency, impelling the potential applications of MnTe-based thermoelectric materials as a robust candidate for waste heat recovery.

The efficiency of Bi2Te3thermoelectric generators is strongly constrained by the fact that n-type alloys always perform poorly thermoelectrically compared to their p-type counterparts. Here, we report an efficient method for improving the thermoelectric performance of n-type Bi2Te2.69Se0.33Cl0.03by incorporating Ag8SnSe6. The incorporation of Ag8SnSe6increases the carrier effective mass as a result of dissolved Ag and Sn atoms in Bi2Te2.69Se0.33Cl0.03, which in turn enhances the Seebeck coefficient. The thermal conductivity of Bi2Te2.69Se0.33Cl0.03also decreases due to multiscale phonon scattering from both the residual Ag8SnSe6second phase and point defects. Consequently, we achieve a high ZT of 1.24 at 353 K and a high average ZT of 1.12 for temperatures in the range of 300–433 K in Bi2Te2.69Se0.33Cl0.03 + 1 wt% Ag8SnSe6, which are respectively ∼ 27.42% and ∼ 26.78% larger than those of Bi2Te2.69Se0.33Cl0.03. Furthermore, a device with two couples of n-p thermoelectric legs based on 1 wt% Ag8SnSe6n-type legs shows a greater cooling temperature drop (28%) than that of the Bi2Te2.69Se0.33Cl0.03n-type legs device. The high thermoelectric and mechanical performance (83.4 HV) of Ag8SnSe6incorporation in n-type Bi2Te3makes them strong candidates for practical applications.

In this work, the co-doping in both the anion and cation sites of SnTe has been implemented by addition of BiCl3and the effect of co-doping on thermoelectric performance of SnTe-based materials has been studied detailedly. Benefitting from the sharp reduction of carrier concentration and the increase of density of states due to the electron donor contribution of Bi and Cl, the electrical transport properties have been improved greatly; moreover, the hierarchical architectures such as the point defects, dislocations, nano-particles and phase/grain boundaries act as multiscale phonon scattering centers and effectively suppress the transport of phonons in wide frequency range, thus reduced the thermal conductivity dramatically. Due to the synergistic regulation of cation-anion co-doping, a maximum ZT of ~1.27 at 873 K has been obtained in the sample of SnTe doping with 4% BiCl3, which enhances by 182% in comparison with the pristine sample.

For a typical perovskite solar cell (PKSC), the electron transport layer (ETL) has a great effect on device performance and stability. Herein, we manifest that low-temperature solution-processed ZnSe can be used as a potential ETL for PKSCs. Our optimized device with ZnSe ETL has achieved a high power conversion efficiency (PCE) of 17.78% with negligible hysteresis, compared with the TiO2based cell (13.76%). This enhanced photovoltaic performance is attributed to the suitable band alignment, high electron mobility, and reduced charge accumulation at the interface of ETL/perovskite. Encouraging results were obtained when the thin layer of ZnSe cooperated with TiO2. It shows that the device based on the TiO2/ZnSe ETL with cascade conduction band level can effectively reduce the interfacial charge recombination and promote carrier transfer with the champion PCE of 18.57%. In addition, the ZnSe-based device exhibits a better photostability than the control device due to the greater ultraviolet (UV) light harvesting of the ZnSe layer, which can efficiently prevent the perovskite film from intense UV-light exposure to avoid associated degradation. Consequently, our results present that a promising ETL can be a potential candidate of the n-type ETL for commercialization of efficient and photostable PKSCs.

For a typical perovskite solar cell (PKSC), both the electron transport layers (ETLs) and hole transport materials (HTMs) play a very important role in improving the device performance and long-term stability. In this paper, we firstly improve the electron transport properties by modification of TiO2ETLs with Na species, and an enhanced power conversion efficiency (PCE) of 16.91% has been obtained with less hysteresis. Subsequently, an inorganic CuI film prepared by a facile spray deposition method has been employed to replace the conventional spiro-OMeTAD as the HTM in PKSCs. Because of the improved transport properties at the ETL/perovskite and perovskite/HTM interfaces, a maximum photovoltaic efficiency of 17.6% with reduced hysteresis has been achieved in the PKSC with both the Na-modified TiO2ETL and 60 nm-thick CuI layer HTM. To our knowledge, the PCE achieved in this paper is one of the highest values ever reported for the PKSC devices with inorganic HTMs. More significantly, the PKSCs exhibit an outstanding device stability, their PCE remains constant after storage in the dark for 50 days, and they can retain approximately 92% of their initial efficiency after storage even for 90 days.

The carrier non-radiative recombination loss caused by numerous interfacial defects existing between perovskite and neighboring charge transport layers, such as SnO2/perovskite and perovskite/spiro-OMeTAD, which greatly restricts the performance improvement of flexible perovskite solar cells (PSCs). Herein, we devised a novel dual-modification strategy using Ce-containing compounds (Ce2(SO4)3and Ce(SO4)2) to minimize interfacial defect density at the interface of SnO2/perovskite and perovskite/spiro-OMeTAD respectively, thus enhancing the performance and stability of flexible PSCs. It was revealed that the introduction of Ce2(SO4)3interface layer was conducive to ameliorating the electrical properties of SnO2and significantly reducing the SnO2/perovskite interface defects. Moreover, the Ce(SO4)2was adopted as a novel oxidant to achieve the rapid oxidation of spiro-OMeTAD, thus enhancing the hole mobility of bulk spiro-OMeTAD and suppressing perovskite/spiro-OMeTAD interface defects. Therefore, reduced non-radiative recombination losses near the two interfaces of the perovskite layer could be achieved by such a novel and comprehensive modification strategy. In consequence, the Ce-modified flexible and rigid PSCs achieved excellent photoelectric conversion efficiency (PCE) of 19.34 % and 22.62 %, respectively. Notably, the optimized flexible PSCs exhibited outstanding mechanical durability, and 83.2 % of the initial PCE was maintained after 3000 bending cycles.