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MoS2 thin film is deposited on ITO/CdS substrate by in-situ hydrothermal method, which is expected to be a potential absorber material for planar heterojunction solar cell due to its high absorber coefficient and carrier mobility. The CdS buffer layer provides a robust template for the quasi-epitaxial growth of MoS2 with (0 0 2) preferred orientation by enjoying the analogical hexagonal structures and the shared sulfur atoms, resulting in a benign interface of CdS/MoS2. Then a device with ITO/TiO2/CdS/MoS2/Carbon-Ag structure is assembled after coating carbon-Ag electrode. The effects of the growth characteristics, morphology changes and optical properties of MoS2 on the device performance are studied systematically. Finally, a primary efficiency of 0.12% is achieved using a P-type MoS2 absorber with a thickness of 305 nm, exhibiting an outstanding stability. The one-dimensional solar cell capacitance simulator (SCAPS) is further used to reveal the bottleneck of device performance. After optimizing the doping density (1 × 1015 cm−3) and defect density (

Doped PbPdO2 materials have attracted much attention as a spin gapless semiconductor (SGS) with the important properties of colossal electroresistance (CER) and giant magnetoresistance (GMR). In this study, the PbPdO2 thin films with (002) preferred orientation were prepared by pulsed laser deposition (PLD), and the temperature dependences of resistance and resistivity, R (T) and ρI (T), were measured under different applied DC currents. Remarkably, a positive CER effect induced by the current was firstly observed in the PbPdO2 films. In particular, it is novelty found that the positive CER value of PbPdO2 with I = 10 μA and T = 10 K reached about 300%. Moreover, the cyclic ρI (T) curves were also measured for I = 0.01 and 10 μA going back and forth between 10 K and 400 K. The time dependences of ρt/ρ0 ratio with T = 100 K, 300 K, 400 K and I = 0.01 and 0.1 μA were also obtained. A critical temperature Tc with about T = 260 K for all applied currents was found. As T > Tc，the band gap of the film is enhanced by the combined effect of the temperature and current. At the same time, Pb and O vacancies, and the evolution of oxygen valence states in the PbPdO2 film were observed by energy dispersive spectrometer (EDS), electron paramagnetic resonance (EPR) and in-situ x-ray photoelectron spectroscopy (XPS). Especially, the charge transport between O1− and O2− was confirmed by in-situ XPS. Finally, based on first-principles calculation, an internal electric field model and its induced potential barrier were established, which well explains the positive CER effect and the critical temperature Tc.

Hydrothermal deposition is emerging as a highly potential route for antimony-based solar cells, in which the Sb2(S,Se)3 is typically in situ grown on a common toxic CdS buffer layer. The narrow band gap of CdS causes a considerable absorption in the short-wavelength region and then lowers the current density of the device. Herein, TiO2 is first evaluated as an alternative Cd-free buffer layer for hydrothermally derived Sb2S3 solar cells. But it suffers from a severely inhomogeneous Sb2S3 coverage, which is effectively eliminated by inserting a Zn(O,S) layer. The surface atom of sulfur in Zn(O,S) uniquely provides a chemical bridge to enable the quasi-epitaxial deposition of Sb2S3 thin film, confirming by both morphology and binding energy analysis using DFT. Then the results of the first-principles calculations also show that Zn(O,S)/Sb2S3 has a more stable structure than TiO2/Sb2S3. The resultant perfect Zn(O,S)/Sb2S3 junction, with a suitable band alignment and excellent interface contact, delivers a remarkably enhanced JSC and VOC for Sb2S3 solar cells. The device efficiency with the TiO2/Zn(O,S) buffer layer boosts from 0.54% to 3.70% compared with the counterpart of TiO2, which has a champion efficiency of Cd-free Sb2S3 solar cells with a structure of ITO/TiO2/Zn(O,S)/Sb2S3/Carbon/Ag by in situ hydrothermal deposition. This work provides a guideline for the hydrothermal deposition of antimony-based films upon a nontoxic buffer layer.

Antimony chalcogenide Sb2(S, Se)3 is attracting a lot of attention as photovoltaic absorber owing to its rewarding photoelectric properties, low toxicity, and earth abundance. However, its device efficiency is still limited by the absorber material quality and device interface recombination. In this work, a fluorine-doped tin oxide (FTO) substrate with ultra-thin SnO2 layer and a low-cost stabilized carbon paste are introduced as a front and back contact layer respectively in Sb2(S, Se)3 based planar solar cells. Over 5.2 % efficiency is demonstrated in the structure of FTO/SnO2/CdS/Sb2(S, Se)3/Carbon/Ag, where the Sb2(S, Se)3 is prepared by hydrothermal technique. The complementary device physics characterizations reveal that the interfacial recombination between TCO and CdS is significantly suppressed by the introduction of ultra-thin SnO2 layer, which is profited from the leakage protection and bandgap offset engineering by its high resistivity and suitable conduction band minimum. Meanwhile, the successful adoption of the low-cost stabilized carbon as a back contact here shows an enormous potential to replace the conventional organic hole transport materials and noble metal. We hope this work can provide positive guidance to optimize Sb2(S, Se)3 based planar solar cells in the future.

Sulfurization is an inevitable process for depositing high-quality Cu2ZnSnS4 (CZTS) thin films, which usually are implemented under high vacuum or inert atmosphere. In this work, a novel ambient-ai...

PbPdO2 and M-doped PbPdO2 (M = Cu, Co, Fe) films were prepared using pulsed laser deposition (PLD) method. The structures, electrical and magnetic properties were systematically investigated by XRD, Raman, SEM, XPS, AFM and VSM. Our results indicate that PbPdO2 and PbPd0.9M0.1O2 (M = Cu, Co, Fe) film with (0 0 2) preferred orientation can be well fabricated. The valence states of magnetic atoms in M-doped PbPdO2 (M = Cu, Co, Fe) thin films are identified to be Cu1+, Co2+,3+ and Fe3+, respectively. All Pb(Pd,M)O2 (M = Cu, Co, Fe) films exhibit ferromagnetism with high metal-insulator transition temperatures at around 330–370 K. Moreover, the resistivity of Fe doped PbPdO2 film is higher than that of the pristine PbPdO2 film, while the resistivities of Co and Cu doped PbPdO2 films are lower. At the same time, Fe, Co and Cu dopants do enhance the ferromagnetism of PbPdO2 film, while the enhancement of magnetic moment for Fe dopant is most evident. Lastly, based on Pb vacancy and O−1 observed experimentally, the band gaps and magnetic moments of Pb(Pd,M)O2 films were calculated by first-principles, and the results explain well the experimental facts.

Base on the Monte Carlo simulation and fast Fourier transformation micromagnetism (FFTM) method, the magnetic dynamic properties of defective Cobalt (Co) nanorings are studied. The simulated results indicate that the hysteresis loops of Co nanorings with small defect are similar to those of the symmetric nanorings. However, when the area of defect increases, the magnetization process of the defective Co nanorings is different from that of symmetric Co nanorings. It is found that the remanence (Mr) of the system increases at first and then decreases with the increase of defect location. Nevertheless, there is a relative stable region in which Mr almost do not change with the defect location varying when the defect is small. The simulated results are well analyzed through the evolution of spin-configurations (SCs) of the defective Co nanorings. The investigation about magnetic dynamic properties of the defective Co nanorings may provide reference for their application in high-density data storage.

Germanium selenide (GeSe), a IV-VI chalcogenide containing earth-abundant and low-toxic elements, has attracted increasing interest as a potential absorber material for photovoltaics due to its excellent optical and electrical properties. In this work, a simple and effective magnetron sputtering method was proposed to deposite GeSe precursor thin films using GeSe alloy target. Subsequently, the as-deposited samples were post-annealed in vacuum atmosphere. The effects of different annealing temperatures on crystallinity, morphology and phase transformation of the as-prepared films were systematically investigated. It has been revealed that phase-pure and uniform GeSe thin films were obtained through the self-decomposition of slight GeSe2 impurity at 400 °C. Finally, a prototypical FTO/CdS/GeSe/C-Ag solar cell with 220 mV open circuit voltage and 0.05% power conversion efficiency was fabricated, which suggests the potential of sputtering processed GeSe thin film for low cost solar cell.

Sb2(S,Se)3 are considered as a promising absorber material for solar cells owing to its earth-abundant, nontoxic constituent, simple phase and long-term durability. In this work, a facile chemical bath deposition followed by post-selenization was introduced to prepare Sb2(S,Se)3 thin film, which leads to a graded band gap structure. The sulfoselenide Sb2(S,Se)3 thin films with smooth morphology were obtained through optimizing the selenization process. Meanwhile, a low cost and substitutable carbon electrode was used as hole selection material. Sequentially, the full-inorganic Sb2(S,Se)3 device with efficiency of 2.64% was also fabricated according to structure of FTO/CdS/Sb2(S,Se)3/Carbon, which is the highest value in CBD processed FTO/CdS/Sb2(S, Se)3/Carbon solar cells.

In this work, Cu2ZnSnS4 (CZTS) thin film was successfully prepared from four types of mixed binary sulfides nanoparticles under inert Ar atmosphere. A comparison study was conducted to explore the effect of binary sulfides with different value states on the CZTS thin films. Through X-ray diffraction (XRD), Raman and scanning electron microscopy (SEM), the pure CZTS phase can be obtained independent of the value states. However, distinguished crystallinity and morphology of CZTS were observed by using binary precursor with different value states. The grain size up to 1 µm was achieved by annealing (Cu2S+ZnS+SnS2) precursor without additional sulfur atmosphere, suggesting that value state of binary sulfides precursor play an important role in CZTS growth. This result also agrees well with our theoretical prediction. Finally, appropriate ratio of Cu/Zn/Sn was evidenced to yield an enhancement in power conversion efficiency from 0.09% (stoichiometric ratio) to 0.55% (Cu-poor, Zn-rich).

Ternary Cu2SnS3 (CTS) thin films have attracted lots of attention due to its low cost, nontoxic element for solar cell. However, Tin losses always happen during sulfurization, which will affect the phase purity and morphology of CTS thin films and relevant solar cell. In this work, a low cost oxides route was used to prepare CTS thin films. The influences of sulfurizaton temperature on the crystal structure, morphology and composition were studied carefully. From the XRD, SEM and EDX results, it was found that the stable oxides were conducive to alleviate the Sn loss even at the higher sulfurization temperature (580 °C). Meanwhile, the crystal structure evolution along annealing temperature was also observed from mixed phase (Monoclinic and Tetragonal) to single phase Monoclinic. The Monoclinic CTS thin films sulfurized at 580 °C were used to fabricate CTS solar cell with Mo/CTS/CdS/ZnO/AZO/Ag structure, exhibiting efficiency of 0.16%. The comparable Voc of 300 mV was achieved by benefiting from the precise composition control. Besides, the photoelectric properties of the device were carefully studied as well. This study provides a low-cost and facile strategy for the fabrication of Sn-loss free CTS solar cells.

In this work, Cu2MSnS4 (M: Zn, Mn, Cd) thin films were successfully prepared by a low-cost and facile oxide-based route. After sulfurization of oxides precursor, the Cu2MSnS4 thin films with composition control exhibit good morphology, analogous crystal structure and suitable bandgaps. Finally the preliminary solar cells based on these films show proper power conversion efficiencies, which demonstrate a high potential application in low cost thin film solar cells.

The inhibition and removal of the SnS2 impurity phase in the kesterite Cu2ZnSnS4 (CZTS) layer is a major challenge for the improvement of CZTS solar cells; this impurity phase can critically damage device performance by forming a diode and a barrier for carrier collection. However, the formation and growth mechanism of SnS2 is incomplete and the common etching treatment with (NH4)2S is problematic because of its toxic characteristics. In this study, the formation and growth of large-size SnS2 sheets were observed to occur on the surface of the CZTS thin film via condensation during the cooling process. Sequently, a novel and benign peeling process was carried out using a sticky tape to effectively remove the SnS2 formed on the surface, resulting in a uniform CZTS thin film. A maximum efficiency of 4.3% of the oxides-derived CZTS device was obtained after this mechanical exfoliation, which is nearly eleven times that of the device without stripping. It was confirmed that this surface treatment is an effective and green way to remove the SnS2 impurity, which largely improved the performance of the CZTS device and may guide the preparation of pure phase CZTS thin films.

Extreme magnetoresistance in nonmagnetic compounds has received considerable attention because this phenomenon challenges the classical understanding of electron transport under a magnetic field. In this study, YBi, which crystallizes in a NaCl-type structure, was synthesized via self-flux method to study its magnetotransport properties and electronic structure. Under zero magnetic field, metallic behavior was observed in the whole temperature interval ranging from 2 to 300 K. Interestingly, extreme magnetoresistance and a resistivity plateau developed when the applied magnetic field was increased; the magnetoresistance reaches 0.8 × 105% at 9 T and 2 K. Multiple bands including one electron pocket and two hole pockets revealed by Kohler's rule and first-principle calculations were responsible for the transport processes. Moreover, the hidden band inversion was also uncovered, which suggests the existence of a topological nature in this compound. The contribution of a single Fermi pocket and the combination thereof for magnetotransport indicate that electron–hole compensation plays an important role in determining the electric properties. All these results point towards YBi being a semimetal member of the RPn family (R = rare earth; Pn = Sb and Bi).

In this work, CuO ( 1 ¯ 1 1 ) preferred orientation thin films with nano wheatear array have been prepared by using reactive magnetron sputtering. Their structures, physical properties were measured, and the surface energies of CuO films were calculated by first-principle calculations. Especially, single nanowire electronic measuring method based on conductive atomic force microscopy (C-AFM) and Kelvin probe force microscopy (KPFM) were developed. The prepared CuO films with nano wheatear array have good crystallinity. Here, wheatear is an ear of wheat, and the morphology of nanowire is similar to that of the wheatear. It is found that the band gaps of CuO films can be modulated from 1.54 to 1.25 eV by changing length of nano wheatear. Moreover, the measured results by KPFM show the existence of the p-type carrier, the decrease of the band gap with increasing length of nano wheatear. At the same time, the applied electric field (E) dependence of the current density (J) for single nano CuO wheatear was measured by C-AFM. The experimental results in the injection and direct tunnel regimes indicate that, with increasing length of nano CuO wheatear, the work function is enhanced and the band gap is decreased. The measured results on work function and band gap by C-AFM are consistent with those by KPFM. At last, it is suggested that KPFM and C-AFM can provide both effective methods in measuring the band gap of the semiconductor.

PbPdO2, PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2 thin films with body-centered orthorhombic structure were prepared by PLD technique, respectively. Their structures, magnetic and electrical properties were measured by XRD, SEM, AFM, EDS, XPS and VSM, respectively. The experimental results indicate that the three samples all have the preferred orientation of (002), and room temperature ferromagnetism. From EDS and XPS results, we can deduce that there exist Pb vacancies in the three samples. Meanwhile, the valence states for Pb, Pd, O, Gd and V ions were found to be 2+, 2+, 2−, 3+ and mixed 4+ and 5+, respectively. It was also found that the magnetic moments of PbPdO2 and PbPd0.9Gd0.1O2 are least and largest, respectively. Moreover, the electrical characteristics analysis indicates that the electrical resistivity is enhanced by V ion substitution, but reduced by Gd ion substitution. In addition, the significant insulator–metal transition temperatures of PbPdO2, PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2 were found to be about 385 K, 390 K and 430 K, respectively. Finally, according to the experimental facts of Pb vacancies in the three samples, the first-principles calculated models containing Pb vacancies were established. The calculated results explain well the magnetic origin of PbPdO2, and V and Gd doping roles on its electrical and magnetic properties.

Selenization is a key process to prepare Cu 2 ZnSnS x Se 4-x (CZTSSe) thin films from sulfide for high efficient solar cell. To explore the effect of annealing atmosphere on the substitution of S by Se in Cu 2 ZnSnS 4 (CZTS) thin films, different selenization atmosphere (Vacuum or Ar) are used. By examining the annealed sample, it is found that selenization under Ar atmosphere replaces S with Se more efficiently, resulting large grain and small band-gap. The reaction kinetics has been studied to explore such phenomena. It demonstrates that the substitution reaction is enhanced when the flowing Ar carries off S gas. Finally, the effect of annealing atmosphere on oxide-based CZTSSe devices has also been studied. The Vacuum selenized CZTSSe device shows a higher efficiency of 4.4%, due to the more appropriate band-gap. To the best of our knowledge, this is the best device performance in oxides nanoparticles-derived CZTSSe solar cell.

We have fabricated PbPdO 2 nano-particles and PbPdO 2 films with (211) preferred orientation (sample A) and with (002) preferred orientation (sample B), respectively. The structures and physical properties were measured by XRD, Raman, SEM, XPS and AFM. The experimental results indicate that the PbPdO 2 films have granular structure with the grain size of about 200 nm and some Pb vacancies exist in both samples. It is found that PbPdO 2 with (002) preferred orientation has near zero-gap, while PbPdO 2 with (211) preferred orientation has larger band gap. This surface anisotropy band gap is also proved by our first principles band structure calculations. Moreover, one notices that the sample B possesses lower resistivity than sample A, and both samples possess a wide insulator-metal transition temperature ( T MI ) with around 370 K.

The substitution of Sn with Ge is one of the promising approaches to fabricate high-efficiency Cu 2 ZnSn 1-x Ge x S(e) 4 (CZTGS(e)) thin-film solar cells, especially for the multijunction or bandgap-graded solar cells. However the evolution of structure and optical properties of CZTGS(e) in a wide composition range (0 ≤ x ≤ 1) hasn't been researched and elucidated systematically. In this paper, CZTGS(e) films were synthesized by selenizing or sulphidising oxide precursors, and their optical, componential and structural property were investigated by absorption spectroscopy, scanning electron microscopy and X-ray diffraction (XRD)/Raman, respectively. The insertion of germanium into the lattice of Cu 2 ZnSnS(e) 4 (CZTS(e)) is verified by relevant XRD peaks and Raman vibrational modes, as both of them shift towards higher diffraction angles and wave-numbers respectively. Besides, the spectrum of absorption revealed that the bandgap of CZTGS(e) can be widely adjusted between 0.96 and 2.0 eV. The preliminary solar cells show that the Voc increases with the increase of bandgap, while the Jsc exhibits opposite tendency. This can be expected to be applied in full solar spectrum absorption.

The sulfurization is an essential process during the preparation of high quality Cu2ZnSnS4 (CZTS) absorber layers, which is controlled by the parameters such as annealing time, temperature and atmosphere, etc. The heat under different temperature not only provides energy for the samples, but also determines the sulfur vapor pressure, which affects the CZTS growth. To distinguish the effect of energy supply and sulfur vapor pressure on CZTS films, a two-temperature zone tube furnace was used, which permits independent control of the sulfur source and substrate temperature. Keeping the substrate temperature constant, the morphology and crystalline of CZTS thin films were investigated under various sulfur vapor pressure by changing sulfur temperature. Finally, the device performances have also been studied, which depended significantly on the sulfur vapor pressure. A champion PCE (2.59%) of oxide-derived CZTS device was obtained under high sulfur vapor pressure.

In this study, a simple and novel oxide-nanoparticles-based process was applied to prepare Cu2FeSnS4 (CITS) thin films. Firstly, the low cost and naturally abundant oxides (e.g. CuO, Fe2O3 and SnO2) were coated on the glass substrate. Secondly, CITS thin films were grown through the sulfurization of oxides precursors in a low toxic sulfur atmosphere. To investigate the phase transformation during sulfurization, the different annealing temperatures were used. It was found that the intermediate phase Cu3SnS4 and Cu2Sn3S7 existed during the CITS growth. Finally, the phase-pure CITS films with large grains were obtained when the sulfurization temperature increased to 580 °C. Furthermore, an obvious photoelectric response of CITS thin film is displayed, which suggests its potential application as one kind of low cost solar absorber materials.

Understanding the formation mechanism of the secondary phases in Cu2ZnSnS4 (CZTS) absorber layer is necessary for the development of CZTS thin films solar cells. With this aim, the XRD, Raman and SEM were used to investigate the phases coexistence in CZTS thin films grown under different copper content. The surface of the Cu-rich CZTS thin films is rough, and the secondary phase CuxS emerges as front surface phases. Besides, another secondary phase ZnS segregates towards both front and back regions of off-stoichiometric CZTS thin films (Cu rich or Cu poor), which was evidenced by the 2nd and 3rd order of ZnS using Raman analysis excitated at 325 nm. The pure phase CZTS exists only as its composition was stoichiometric. So the preparation of pure phase CZTS is sensitive to composition, suggesting that the precise composition control plays an important role in CZTS growth.

GeSe is considered as a potential absorber material for thin film solar cells owing to its ideal band gap, strong light absorption, remarkable air durability, Earth-abundance and non-toxic constituents. However, the high vapor pressure of GeSe at a temperature below its melting point makes it difficult to synthesize a high-quality GeSe film. To alleviate this limitation, in this work, a thermal evaporation combining a novel sandwiching post-annealing method was introduced to deposit high quality GeSe thin films with (100)-orientation. The self-assembling mechanism of the highly oriented GeSe film was carefully investigated by the systematic experiments and confirmed by the lowest total energy of the (100) crystal plane. Finally, the fully-inorganic, low-cost and non-toxic planar device with the superstrate configuration of FTO/TiO2/GeSe/carbon/Ag was also successfully fabricated. Notably, as a result, an impressive open circuit voltage (VOC) of 340 mV (maximum: 456 mV) was achieved, which is the highest VOC of GeSe solar cells reported so far. Furthermore, through current-voltage, capacitance-voltage profiling and drive level capacitance profiling measurements, it was demonstrated that the limiting factors of the GeSe solar cell performance were the narrow depletion width (138 nm) and the drastic recombination at the TiO2/GeSe interface.

Molecular solution with the metal-thiourea complex is a facile and effective route for Cu2SnS3 (CTS) thin film deposition. However, its stability is still challenging due to flexible metal salts precursors. Here we report a strategy to enhance the stability of the Cu–Sn–S molecular solution that use bivalent Sn to suppress the oxidation of the S2- of thiourea via the redox reaction. The self-stabilizing mechanism has been carefully revealed by the systematic experiments and confirmed by the spontaneous reaction process of metal-thiourea system. It demonstrates that Sn with a low valence state weakens the transfer of lone pair electrons from thiourea to Cu2+ and Sn4+ ions, alleviating the sulfur precipitates from thiourea oxidation because of the easily reducible character of Sn2+ ion. The solution with Sn2+ antioxidant additive can be stored for a long time under air ambient, which is then spin-coated and sulfurized with Sn powder compensation. The uniform CTS thin film with composition control is finally achieved and delivers a device efficiency of 1.15%. This work provides a guide on stabilizing the solution precursor for chalcogenide thin film deposition.

The future development of Cu 3 SbS 4 as an alternative absorber for low cost and high efficiency thin film solar cell depends strongly on the understanding of the formation of mechanism in this system. With this aim, a detailed characterization of Cu 3 SbS 4 particles prepared by microwave irradiation is presented, combining XRD, SEM, and EDX. The development of Cu 3 SbS 4 formation with the increasement of temperature and the prolongation of time are investigated by depth-resolved analysis. Under such conditions, a reaction pathway for the formation of Cu 3 SbS 4 from binary and CuSbS 2 compounds as intermediates is proposed. The experimental data supports a formation mechanism of Cu 3 SbS 4 that proceeds rapidly when the CuSbS 2 react with the remaining binary phases CuS. During reaction Cu is completely consumed, while Sb is lost through the way of Sb 2 S 3 vapor.

As one typical example of third-generation thin-film solar cells, Dye-sensitized Solar Cell (DSSC) has become a research hot-spot because of its advantages. As a basic electron transport material, the modification of the nano-crystalline TiO2 would have remarkable influence on the cell. In this work, the scattering layer was firstly fabricated on the conductive glass substrate by sol–gel dip-coating method for the stable and high efficiency conventional DSSC. And the effect of the modification of the nanocrystalline TiO2 photoanode by the tetrabutyl titanate sol was investigated. Practically, the cell with photoanode modified by tetrabutyl titanate sol obviously presents higher light-electric conversion efficiency.