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The strong anisotropic electrical properties of one-dimensional (1D) nanostructure semiconductors, especially the anisotropic carrier transport, have a negative and significant influence on the performance of solar cells if the nanostructures have random orientation. Considering the advantages of nanorod solar cells in carrier transport, we have achieved growth of vertically aligned Sb2Se3 nanorod array with highly (hk1) orientation on CdS substrate, and constructed superstrate nanorod solar cells for the first time. The Sb2Se3 nanorod array solar cells exhibit the more efficient and long-range carrier transport in vertical direction. Furthermore, in order to suppress interface recombination, a CuInSe2 quantum dots (QDs) sensitizer has been applied to fill the volume between the nanorods completely, thus forming an interpenetrating nanocomposite structure. The CuInSe2 QDs can harvest additional light by absorption of visible light and contribute photocurrent. Meantime, the QDs function as a hole transport material and thus reduce the dependence of lateral transport. Consequently, the interpenetrating nanocomposite CuInSe2/Sb2Se3 solar cells display a power conversion efficiency of 7.54% with significant enhancements in the short-circuit current density and open-circuit voltage over pure Sb2Se3 nanorod cells. This is the highest efficiency for superstrate solar cells based on Sb2Se3 nanorod arrays.

Thin films of perovskite deposited from solution inevitably introduce large number of defects, which serve as recombination centers and are detrimental for solar cell performance. Although many small molecules and polymers have been delicately designed to migrate defects of perovskite films, exploiting credible passivation agents based on natural materials would offer an alternative approach. Here, an eco-friendly and cost-effective biomaterial, ploy- l -lysine (PLL), is identified to effectively passivate the defects of perovskite films prepared by blade-coating. It is found that incorporation of a small amount (2.5 mg mL−1) of PLL significantly boosts the performance of printed devices, yielding a high efficiency of 19.45% with an increase in open-circuit voltage by up to 100 mV. Density functional theory calculations combined with X-ray photoelectron spectroscopy reveal that the functional groups ( NH2, COOH) of PLL effectively migrate the Pb-I antisite defects via Pb-N coordination and suppress the formation of metallic Pb in the blade-coated perovskite film. This work suggests a viable avenue to exploit passivation agents from natural materials for preparation of high-quality perovskite layers for optoelectronic applications.

Designing a durable lithium metal anode for solid state batteries requires a controllable and uniform deposition of lithium, and the metal lithium layer should maintain a good interface contact with solid state electrolyte during cycles. In this work, we construct a robust functional interface layer on the modified Li-B electrode which considerably improves the electrochemical stability of lithium metal electrode in solid state batteries. It is found that the functional interface layer consisting of polydioxolane, polyiodide ion and LiTFSI effectively restrains the growth of lithium dendrites through the redox shuttle reaction of I−/I3− and maintains a good contact between lithium anode and solid electrolyte during cycles. Benefit from these two advantages, the modified Li-B anode exhibits a remarkable cyclic performance in comparison with those of the bare Li-B anode.

CdTe has become a leading contributor in the thin-film photovoltaic market. A suitable back contact is still one of the most crucial issues to realize efficient CdTe thin film solar cells. Herein, we intensively studied the mechanisms of interfacial modification and device performance enhancement for the representative ZnTe:Cu back contact structure. It’s found that, in spite the as-deposited ZnTe:Cu buffer could reduce the contact barrier, the device performance is still limited by the increased defect-related recombination. A controlled heat treatment process is proved to be effective in alleviating the recombination loss at the back contact. Detailed characterizations demonstrate that the CdTe/ZnTe:Cu interface reaction happens and the interfacial composition is modified during the heat treatment process, which optimize the interfacial chemical states and band alignment. The improved interfacial properties decrease the defect-related recombination and promote the holes transport, and consequently improve the device efficiency greatly.

In this study, nickel oxide (NiOX) thin films were prepared by direct current (DC) reactive magnetron sputtering. The various properties of NiOX thin films including deposition rate, morphology, electrical and optical properties as well as grain structure and chemical composition were systematically investigated. The material properties of NiOX were finely modified under the monitoring of target voltage during sputtering. NiOX thin films were applied as hole transport layers (HTLs) in all-inorganic CsPbI2Br perovskite solar cells (PSCs). The highest efficiency of 12.6% had been achieved for the optimized all-inorganic CsPbI2Br PSCs with the inverted structure of Glass/FTO/NiOX(HTL)/CsPbI2Br/ZnO@C60 (electron transport layer, ETL)/Ag. The PSC still yielded over 90% of its initial power output after 10 h operation without encapsulation.

Conjugated polymers are commonly used as effective hole transport materials (HTMs) for preparation of high-performance perovskite solar cells. However, the hydrophobic nature of these materials renders it difficult to deposit photovoltaic perovskite layers on top via solution processing. In this article, we report a generic surface modification strategy that enables the deposition of uniform and dense perovskite films on top of non-wetting interfaces. In contrast to the previous proposed chemical modifications which might alter the optoelectronic properties of the interfacial layers, we realized a nondestructive surface modification enabled by introducing a layer of insulating mesoporous aluminum oxide (Al2O3). The surface energies of the typical non-wetting hole-transport layers (PTAA, P3HT, and Poly-TPD) were significantly reduced by the Al2O3 modification. Benefiting from the intact optoelectronic properties of the HTMs, perovskite solar cells deposited on these interface materials show full open-circuit voltages (VOC) with high fill factors (FF) up to 80%. Our method provides an effective avenue for exploiting the full potential of the existing as well as newly developed non-wetting interface materials for the fabrication of high-performance inverted perovskite solar cells.

In this study, sodium doped molybdenum (Mo:Na) and Mo thin films are deposited at different working pressures under the excitation of the radio frequency (RF) or direct current (DC) power supplies for application in Cu(In,Ga)Se2 (CIGS) thin film solar cells. The various material properties including dynamic deposition rate, electrical and optical properties, crystal structure and morphology are systematically investigated and compared for these RF and DC sputtered Mo:Na and Mo thin films. Mo and Mo:Na related back contacts, i.e. bottom Mo:Na layer prepared at a high working pressure and top Mo or Mo:Na thin film sputtered at a low working pressure are employed in CIGS thin film solar cells. CIGS thin film solar cells with Mo:Na (bottom, DC)/Mo:Na (top, DC) have a relatively high VOC, which is related to a relatively easy migration of Na passing through the DC Mo layers and entering into the CIGS thin film solar cells. A CIGS thin film solar cell of 14.0% has been achieved in this work.

Antimony selenide (Sb2Se3) is a promising low-cost and low-toxicity photovoltaic material. The electron buffer layer is of great significance for superstrate Sb2Se3 thin film solar cells. Herein, high-performance Sb2Se3 solar cells were fabricated by using sputtered, bandgap-tunable oxygenated cadmium sulfide (CdS:O) as a novel class of electron buffer layers. The optical transparency and energy band levels of CdS:O buffers were precisely adjusted by controlling the oxygen content in CdS:O layers. With the incorporation of an optimized wide band-gap CdS:O electron buffer layer, the device parameters JSC, VOC and FF were all improved. An efficiency of as high as 6.29% was achieved. It's found that, besides the reduced light absorption in the CdS:O layer, the high-quality CdS:O/Sb2Se3 junction played a vital role in the efficiency enhancement. The optimization of interfacial band alignment and defects passivation by atomic oxygen both contribute to the improved quality of CdS:O/Sb2Se3 heterojunction. This study demonstrates that the sputtered CdS:O is a promising electron buffer layer for preparation of high-efficiency and large-area Sb2Se3 thin film solar cells.

Surface engineering of crystalline silicon (c-Si) is the core of Si-based semiconductor devices. The current commercially available c-Si solar cells achieve this by making use of a conventional thin dielectric film passivation system (TDFPS), including SiO2, Al2O3, SiNx:H and hydrogenated amorphous silicon (a-Si:H) in industry. However, the TDFPS requires high-vacuum and/or high-temperature conditions, which hinders efforts to further reduce the costs of device fabrication. A revolutionized approach to circumvent these issues involves the replacement of TDFPS with new material system which can also achieve high-quality passivation on c-Si surface. Here, we successfully establish and implement a functional group passivation system (FGPS) using a series of functional materials with a sulfonic functional group -SO3H, such as ‘poly(2-acrylamido-2-methylpropanesulfonic acid)’ (PAMPS) and ‘polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene, sulfonated, cross-linkable’ (PS-b-PERB), which can achieve a highly effective passivation on Si surface, resulting in power conversion efficiencies up to 20% when they are applied in the front surface engineering of interdigitated back contact (IBC) solar cells. Furthermore, the FGPS materials inherently allow passivation layer fabrication in lowtemperature and high-vacuum-free conditions. This work provides novel low-cost material strategies without compromise of performance for c-Si surface engineering in the future Si-based photovoltaics.

Li-B alloy can be used as a lithium-metal anode, and this alloy maintains the entire structure of Li7B6 constituents after the removal of free Li. In this study, a compact Li-Al layer which allows electron and ion transport to form in situ on the Li-B electrode was developed to solve the fundamental challenges of the Li-metal anode. Results of symmetric-cell tests show that the Li-Al layer coating on Li-B electrode can improve cyclic life over 1200 h at a current density of 0.2 mA cm−2, whereas bare Li-B electrode has stable cycles not exceeding 800 h. Results of scanning electron microscopy analysis demonstrate that Li deposition occurs beneath the Li-Al layer, and that the Li-Al alloy layer effectively reduces Li-metal corrosion and suppress the formation of Li dendrites. When matched with LiNi0.8Co0.15Al0.05O2 cathode, the Li-B with Li-Al layer shows improved cycle stability and lower voltage difference than bare Li-B anode.

Inverted perovskite solar cells using pristine PEDOT:PSS as the hole-transporting layer (HTL) have been widely studied for its less hysteresis and low-temperature preparation technologies. However, this device suffers from an inferior open-circuit voltage (VOC) and stability problems. Several attempts have made on film formation and interface engineering to improve the efficiency. Modification proved beneficial to decrease energy offset at the interface between the HTL layer and the adjacent perovskite layer. In this paper, modification PEDOT:PSS layers were realized with a dimethyl formamide (DMF) solvent. The sulfonic acid distribution was homogenized in the normal direction after modification. The work function of the modified PEDOT:PSS layers increased from 4.71 to 5.07 eV, and the conductivity of modified PEDOT:PSS increased from 3 × 10−4 to 0.45 S/cm. The as-deposited perovskite films were more uniform with larger grain sizes and less pinholes, resulting in an improved VOC from 0.93 to 1.048 V, while the efficiency was increased from 11.5% to 16.8%. Solar cells without encapsulation under the 50 h and 50% humidity aging test showed 7% degradation of fill factor (FF) with 50 v/v% PEDOT:PSS layer, while the fill factor decreased 11.2% in the 0 v/v% PEDOT:PSS layer, respectively.

Interlayers play important roles in elevating the efficiency of the organic solar cells (OSCs). It is generally believed that organic cathode interlayer (CIL) can form dipole at the interface to reduce the work function of the metal electrode and minimize the contact resistance between the active layer and electrode. However, in most cases, the interlayer materials are deposited onto an active layer by spin coating and the polar groups thus randomly distribute on the surface of the active layer. In this work, we adopted fluorinated polyethylene glycol (FSO-100, a commercialized surfactant) as cathode interlayer in OSCs and achieved remarkable performance enhancement. Scanning Kelvin probe microscopy (SKPM) and ultraviolet photoelectron spectrometer (UPS) results prove that FSO-100 effectively decrease the work function of the metal electrode. Angle resolved XPS (ARXPS) shows that fluorinated alkyl chains on FSO-100 prefer to spontaneously aggregate on one side and thus result in highly ordered ethylene glycol chains, which enhance the dipole strength as well as improve the device performance, even much better than device with polyethylene glycol (PEG) as CIL. These results demonstrate that introducing a fluorinated alkyl chain on CIL is an effective strategy to promote the molecular orientation, as well as improve the electrode modification ability of CIL.

In this study, aluminum doped zinc oxide (ZnO:Al) thin films were prepared by reactive magnetron sputtering from Zn:Al metallic targets with different Al contents (0.5 wt%, 1.5 wt%, 2.0 wt% and 2.5 wt%). The reactive sputtering process was monitored and controlled with a gas loop controller. The crystal structures, morphologies, chemical compositions, optical and electrical properties of the reactively sputtered ZnO:Al thin films were systematically investigated. In addition, the reactively sputtered ZnO:Al thin films were applied as window layers in Cu(In,Ga)Se2 (CIGS) thin film solar cells. The corresponding performances of solar cells were also studied. High efficiency of 16.2% was achieved for CIGS thin film solar cells with reactively sputtered ZnO:Al window layers in this study, which was slightly lower than 17% of reference cell with radio frequency (RF) non-reactively sputtered ZnO:Al window layer.

In this study, molybdenum (Mo) thin films are deposited at different working pressures and different target-substrate distances (Dt-s) (8 cm and 10 cm) under the excitation of the radio frequency (RF) or direct current (DC) power supply for applications in Cu(In,Ga)Se2 (CIGS) thin film solar cells. The various material properties including dynamic deposition rate, electrical and optical properties, crystal structure and morphology are systematically investigated and compared for these RF and DC sputtered Mo thin films. Mo bilayer, i.e. bottom Mo layer prepared at a high working pressure and top Mo thin film sputtered at a low working pressure are employed as back electrodes in CIGS thin film solar cells. CIGS thin film solar cells with DC Mo/DC Mo bilayer have relatively higher efficiency as compared to the others with RF Mo layers, which might be related to a relatively easy migration of sodium (Na) passing through the DC Mo layers and entering into the CIGS absorbers. A high efficiency CIGS thin film solar cell of 16.2% has been achieved in this work.

In this study, the nickel oxide (NiOX) thin films were reactively sputtered at different working pressures in the oxide mode zone for application in flexible all-thin-film electrochromic devices (ATF-ECDs). The working pressure plays an important role on the various properties of the reactively sputtered NiOX thin film including the deposition rate, grain structure (microstructure), morphology, chemical composition, optical properties and electrochemical properties. The flexible ATF-ECDs with ≥2 Pa NiOX thin films perform high optical modulation and relatively fast response time during the electrochromic processes. The detailed electrochromic mechanism is discussed.

Kesterite-based Cu2ZnSn(S,Se)4 quaternary semiconductor solid solutions are emerging as promising materials for low-cost, relatively benign, high-efficiency thin-film photovoltaics. However, the current state-of-the-art Cu2ZnSn(S,Se)4 devices suffer from cation-disordering defects and defect clusters, which generally result in severe band-tailing, considerable interface and bulk recombination, and ultimately unsatisfactory performance. Herein, we report critical growth conditions for obtaining high-quality Cu2ZnSnSe4 absorber layers with the formation of detrimental intrinsic defects largely suppressed. By controlling the oxidation degree of metal elements and modifying the local chemical composition, we essentially modify the local chemical environment during kesterite thin-film growth, thereby effectively suppressing detrimental intrinsic defects. This modification also activates desirable shallow acceptor Cu vacancies, resulting in increased hole mobility and thereby bulk conductivity of Cu2ZnSnSe4 by two orders of magnitude. As a result, we demonstrate 12.5% efficiency devices with greatly reduced band-tailing and enhanced carrier lifetime. These encouraging results demonstrate not only an essential route to overcome the long-standing challenge of defect control in kesterite semiconductors, but also more generally provide an exemplary strategy to improve the electronic quality for a wider range of multinary compound semiconductors.

Recent progress in perovskite photovoltaics has witnessed a growing interest in formamidinium lead iodide (FAPbI3), primarily due to its high efficiency potential and excellent stability. However, the high energy barrier of δ-to-α phase transition presents a major hurdle to fabricate phase-pure α-FAPbI3 layers. Here, we report a two-step phase transition process to deposit high-quality photovoltaic α-FAPbI3 films by printing method. This is realized by judicious selection of a Lewis base N-methyl-2-pyrrolidone (NMP) and its counter Lewis acid, which enables the regulation of intermediary phase to reduce the energy barrier. With fine tuning the phase transition pathway, phase-pure and stable α-FAPbI3 perovskite films are obtained, which yield solar devices with a champion efficiency of 21.35%. The printed mini-modules with active areas of 12.32 cm2 and 55.44 cm2 are also fabricated, giving efficiencies of 17.07% and 14.17%, respectively. This work provides new insights of α-FAPbI3 crystallization for constructing efficient and stable printed photovoltaic devices.

Antimony selenide (Sb2Se3) based thin film solar cells have recently drawn a growing research interest due to their increasing power conversion efficiency, proper bandgap, high absorption coefficient, and earth abundant nature. Herein, the Sb2Se3 thin films were prepared by close spaced sublimation (CSS) for efficient Sb2Se3 solar cells. The origin and the mechanisms of shunt current were analyzed. Non-ohmic space-charge limited current (SCLC) was identified to be an important contribution to the nonlinear shunt current in Sb2Se3 thin film solar cells. To tackle this issue, a high-resistance SnO2 buffer was introduced at the front contact. With the insertion of a SnO2 buffer, the micro-shunt paths were modified and a significant efficiency improvement to 5.18% was obtained.

In the inverted p-i-n perovskite solar cells (PSCs), the widely-used hole transporting layer (HTL) of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) induce degradation problems and hysteresis. To address this issue, several attempts are explored on film formation and interface engineering to improve efficiency. Here, adding alanine into pristine PEDOT:PSS proved beneficial to reconstruct the distribution of the -SO 3 - and -SO 3 H groups, resulting an improvement of the charge collection and transport owing to the weakened enrichment of -SO 3 H. The conductivities of reconstructed PEDOT:PSS films were improved as well as an enhancement of the hydrophobicity. A moderate concentration of alanine could effectively restrain the generation of δ-phase perovskites film and enhance crystallinity of the Cs x FA 1-x PbI 3. The hole trap state of Cs x FA 1-x PbI 3 was slightly reduced to 2.8 × 10 15 cm −3 . The initial power conversion efficiency (PCE) of 15.48% and stable power output (SPO) of 14.5% were achieved, respectively.

Thin-film photovoltaic devices based on chalcopyrite Cu(In,Ga)Se2 (CIGS) material have demonstrated excellent power conversion efficiency. However, developing a low-cost fabrication process with less safety risk that compatible with large-scale production still stands as a major challenge. Using cheap and low toxic element Se vapor to replace the expensive and highly toxic H2Se which is widely used in sputtering-based industrial manufacture is an attractive solution. Received considerable attention, yet the devices fabricated from metallic precursor and element Se vapor still suffer from an inferior performance. In this work, we disclosed the main culprit behind this limitation—the ordered vacancy compounds (OVC) phase at the CIGS/Mo rear interface, which is induced by the drastic out-diffusion of Cu during the selenization. The detrimental OVC phase at the rear interface acts as a blocking barrier, and also results in enhanced rear interface recombination, and weakens the band bending in the hetero-junction, as manifested by the temperature-dependent current-voltage (J-V) measurements, KPFM measurements, and SCAPS-1D simulation. We found that the out-diffusion of Cu and the associated formation of OVC phase at the rear interface can be efficiently suppressed by turning the element Cu and In in as-sputtered precursor into Cu9(In,Ga)4 and Cu9Ga4 alloys using a co-sputtered metallic precursor with a thermal alloying treatment. With the rear interface modification, we significantly improved the device performance, with pronounced increase of Voc and fill factor. Our results indicate even higher efficiency can be achieved by further improving the doping density of the rear interface and optimizing the band gap.

The effects of an Li-Al layer on the modified-Li anode based on solid state batteries are studied. The structure, surface morphology, and cyclic stability of the modified-Li anode are examined by X-ray diffraction spectroscopy, scanning electron microscopy, and electrochemical tests. Results show that interphase layer can prevent Li from reacting with Li1.5Al0.5Ge1.5(PO4)3 and displays a much better cycling stability compared with the bare-Li anode used in symmetric cells. The assembled solid state batteries with modified-Li anode and LiMn0.8Fe0.2PO4 cathode can deliver an initial discharge capacity of 153 mAh g−1 with good cyclic stability and rate performance at 50 °C. The reason for this is that the Li-Al alloy interphase layer can prevent localised Li enrichment, then suppress lithium dendrite growth, and the Li-Al layer on the anode possesses good stability in the presence of Li1.5Al0.5Ge1.5(PO4)3 powder and better interphase contact results between the anode and solid electrolyte in solid state batteries.

Organic-inorganic halide perovskites have attracted huge attentions as the novel photoelectric function materials. So far, perovskite solar cells (PSCs) with prominent performance are still based on the lead halide perovskites, although they are potentially highly toxic. The issue of toxicity has become one of most crucial problems before its commercialization. Therefore, an increasing number of studies have focused on the lead element substitution in PSCs, and many excellent achievements have been reported. Alternative elements, e.g., Sn, Ge, Bi and Sb were successively used to fabricate lead-free perovskites, which provided potential possibility to tackle the toxicity issue. Recently, Sn-Pb hybrid perovskites were demonstrated to realize lead reduction without sacrificing the PCE. In addition, a new family of halide double-perovskites was explored and given high expectations. Here, we give a brief review on the lead substitution in PSCs, including theoretical explorations and experimental achievements, and finally we propose some perspectives.

In this study, MgNd intermetallic is deposited as a thin film using magnetron sputtering. Ultraviolet photoelectron spectroscopy (UPS) is employed to determine the work function of the MgNd thin film. It is found that the MgNd thin film has a low work function of 3.5 eV, leading to its application in hybrid poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS)/n-Si solar cells as a back surface field (BSF) material. By introducing a MgNd thin film into the back Si/electrode interface of a hybrid solar cell, obvious improvements in the open circuit voltage (Voc) and fill factor (FF) of the device are observed, leading to an increase by more than 26% in power conversion efficiency (PCE). Temperature-dependent current density–voltage (J-V) and Voc-light intensity measurements demonstrate that the introduction of a MgNd thin layer increases the built-in voltage at the rear interface and decreases the recombination current in the device. These improvements are attributed to the efficacy of the MgNd thin film as a BSF by reducing minority carrier recombination and enhancing majority carrier transport.

In this study, the annealing treatment on Cu(In, Ga)Se2 (CIGS)/CdS interface in air is systematically investigated under different annealing temperatures from room temperature to 150 °C and different durations. It is found that when CIGS/CdS interface is annealed for a proper duration the corresponding CIGS thin film solar cells show enhanced open circuit voltage (Voc) and fill factor (FF) as well as corresponding conversion efficiency. The capacitance-voltage (C-V) and time-resolved photoluminescence (TR-PL) measurement results indicate that the CIGS thin film solar cells exhibit an increase in net defect density (NCV) and long lifetime for the carriers, respectively, after the annealing treatment of CIGS/CdS at a mediate annealing temperature here. Moreover, the net defect density of annealed solar cells at higher annealing temperatures for a long duration is reduced. All the variations in the solar cell performances, NCV and carrier lifetime would be related to the passivation of Se vacancies and InCu defects, surface (interface) states as well as positive interface discharges and Cu migration etc. A high efficiency CIGS solar cell of 14.4% is achieved. The optimized solar cell of 17.2% with a MgF2 anti-reflective layer has been obtained.

Stabilization of perovskite phases and interfaces in stacked perovskite photovoltaics are critical for their efficiency, operational stability and perovskite solar modules (PSMs). Herein, A-site cation-size mismatch processed perovskite-composition films with less crystal defects are formed by incorporating larger cations formamidinium and methylammonium with smaller cations, i.e., potassium and cesium. The interface stabilization can be achieved by inserting Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine], mesoporous alumina, phenethyammonium ligands and atomic-layer-deposition tin oxides at desired interfaces in inverted perovskite solar cells (PSCs). Thus, the interface defects, non-radiative recombination and ion migration can be remarkably suppressed, resulting in improvement of interface contacts and hole/electron transport. As a result, both cation-size mismatch and interface stabilization (CM-IS) strategies enable hysteresis-free, reproducible 21.9% and 16.9% efficient NiOx-based inverted PSCs and PSMs. Moreover, a high Voc of 1.16 V and 8.05 V can be obtained in large-area PSCs (1 cm2) and PSMs (11.2 cm2) with 7 subcells connected in series. Additionally, the measured T85 lifetime (the time as a function of PCEs decrease to 85% of its initial value) of unencapsulated PSCs under continuous AM 1.5G light illumination is approximately 1000 h.

Perovskite solar cells (PSCs) based on organometal halide (Omh) perovskites have been exhibited superb potential for next-generation photovoltaic applications because of their ever-increasing power conversion efficiencies over the past decade. However, their operational stability remains a challenge, which are attributed to the ionic nature of Omh perovskites and defects of heterojunction interfaces in a stacked solar cell. Thus, stabilization of Omh perovskites phases and device interfaces are of paramount importance towards long-term stable PSCs. This review presents an important tool to explore efficient and stable PSCs by Omh perovskite-based composites and interface stabilization strategies. Moreover, it deals with the study on materials selection for effective design of Omh perovskite composites and cell heterojunction interfaces. The chemical and electrical characteristics of Omh perovskite composites and device interface states, including perovskite film growth, defect tolerance, interface trap passivation, strong chemical interaction, cross-linking and/or chemical bonding, are further discussed. These features provide insights into the stabilization and immobilization of Omh perovskite structures and stacked solar cell interfaces for highly efficient and stable perovskite photovoltaics.

Nickel oxide (NiOX), widely used as ion storage layer in all thin film electrochromic devices (ATF-ECDs), was deposited by reactive direct current (DC) magnetron sputtering at different oxygen fluxes (FO2). The reactive DC magnetron sputtering processes were finely monitored and controlled by the target voltages. The growth model and material properties were systematically investigated. The electrochromic properties for NiOX thin films and corresponding ATF-ECDs were studied as well. The optimal ATF-ECD (SLG/ITO/NiOX/Ta2O5/WO3/ITO) was achieved with a NiOX ion storage layer reactively sputtered at a FO2 of 15 sccm. The electrochromic mechanisms was discussed in details.

The tantalum pentoxide (Ta2O5) thin films used as protonic conductive solid electrolyte layers (SELs) in all thin film electrochromic devices (ATF-ECDs) were widely investigated. The working pressure played a great role in the microstructure and proton transfer of the Ta2O5 thin films. The Ta2O5 thin films were deposited by direct current (DC) reactive magnetron sputtering at different working pressures and growth mechanism was studied. The optical properties, structural properties, chemical compositions, morphologies and protonic conductive properties of the Ta2O5 thin films were systematically investigated. Moreover, the electrochromic properties for corresponding ATF-ECDs with Ta2O5 SELs were studied as well. The ATF-ECD with a 2.0 Pa Ta2O5 SEL exhibited the best device performance with high optical modulation and fast switch speeds.

Controlling the crystallization dynamics is one key in optimizing the performance of perovskite solar cells (PSCs). The present study provides a simple approach using a low temperature stable-transition-film (STF) to prepare highly-dense and pinhole-free CsPbIBr 2 thin film with high crystalline quality, as well as a new structural design (FTO/NiO x /CsPbIBr 2 /MoO x /Au) of all-inorganic perovskite solar cells toward long-term thermal stability. For the first time, we demonstrate that MoO x can independently serve as an outstanding cathode buffer layer on an inorganic perovskite layer. The lower work-function MoO x with ultra-thin thickness (4 nm) leads to decreases of the Schottky barrier, the contact resistance and the interface trap-state density. This increases the power conversion efficiency (PCE) of all-inorganic planar PSCs from 1.3% to 5.52%. Inspiringly, the FTO/NiO x /CsPbIBr 2 /MoO x /Au all-inorganic PSCs were demonstrated to possess excellent long-term thermal stability at high temperatures up to 160 °C.

We proposed a new approach to determination of Judd-Ofelt intensity parameters of Er 3+ doped phosphors via their absorption spectra. To validate this approach, JO parameters of Er 3+ doped BaGd 2 ZnO 5 /PMMA and NaYF 4 /PMMA composites were calculated and in a good agreement with the other glass and crystal. The spontaneous radiative transition probability, branching ratio, and radiative lifetime of the optical transitions were calculated by using the Judd-Ofelt theory. Intense near-infrared emission at 1553 nm was observed under 980 nm laser diode excitation at room temperature. The samples possessing high full-width at half-maximum reach 85 nm have potential application in broadband optical amplifier.

The most important aspect in the development of Si-based photovoltaic technologies is the passivation of the Si wafer surface. Here, we show that Poly(3,4-ethylthiophene):polystyrenesulfonate (PEDOT:PSS) thin films, frequently used in organic/inorganic hybrid solar cells as emitter layers, provide an excellent surface passivation with a millisecond (ms) level effective minority carrier lifetime ( τ eff ). More importantly, we find that this passivation effect is dominated by the PSS species in PEDOT:PSS rather than PEDOT ones. The PSS thin film passivation yields a high τ eff of 9.4 ms on a high-resistivity Si wafer. The interface nature of PSS/Si is unveiled by the X-ray photoelectron spectroscopy and first-principles total-energy calculations together. An electrochemical passivation mechanism is clarified: the Si sub-oxides form at PSS/Si interface by the electrochemical grafting O groups in PSS onto Si surface, which can be controlled by injecting holes or electrons into the Si surface, leading to a switchable interface state between oxidation and deoxidation. To examine the application of the passivation strategy in real devices, we develop a polymer-passivated both-sides Si heterojunction solar cell with light-induced enhancement of photovoltaic performances, which is consistent with the light-induced enhancement of τ eff .

In this study, copper indium gallium di-selenide (Cu(In, Ga)Se2, CIGS) thin films are prepared at different heating temperatures of Se effusion cell (Tsec) between 150 °C and 190 °C. The Tsec has a great influence on the deposition rate, chemical composition, morphology and grain structure of the CIGS absorbers. The CIGS thin film solar cell fabricated at 160 °C shows best efficiency of 11.6% in this series due to the relatively higher open circuit voltage (Voc) and fill factor (FF) as well as a high short circuit current (Jsc). By further optimizing device and material properties, the higher efficiency CIGS thin film solar cell of 17.2% is achieved.

Cu(In, Ga)Se 2 (CIGS) thin film solar cells were grown on polyimide (PI) and soda lime glass (SLG) substrates at low substrate temperatures between 400 °C and 500 °C. Different material properties of the CIGS thin films and photovoltaic performances of the solar cells were systematically investigated. It is found that the (112), (220)/(204) and (116)/(312) peaks from X-ray diffraction (XRD) patterns show double-peak patterns as the substrate temperature decreases. The CIGS thin films grown on both PI and SLG substrates shows layered structures. The bottom and surficial layers of CIGS thin films display small size polycrystalline grains while the middle layers show large size polycrystalline grains. Both types of CIGS thin film solar cells exhibit similar efficiencies while CIGS thin film solar cells grown on PI substrates show lower open circuit voltage and fill factor but higher short circuit current density, as compared to those of CIGS thin film solar cells on SLG substrates. The highest efficiency of 6.14% has been achieved for the CIGS thin film solar cells on PI with the structure of PI/Mo/CIGS/CdS/i-ZnO/ZnO:Al/Al grid here.

The present study investigates the influence of the introduced metallic cation and/or halide anion, e.g. Al3+ and Cl−, on the forming mechanism and electro-optical properties of CH3NH3PbI3 films. Our study shows that introducing of Al impurity into perovskite films produces the intermediate AlI3 that improves the film coverage by expressively slowing down the evaporation of CH3NH3Cl. Likewise, a trace amount of hydrolysis product, i.e. Al2O3, homogenously distribute throughout the precursor as a seed, which is proved to be capable of tuning the crystal orientation and the grain size. Consequently, the introduction of metallic cation and/or halide anion enable the realization of highly crystallized thin film with highly reduced defects, which can effectively alleviate the hysteresis effect that was intractable in planar perovskite cells.

In this work, antimony selenide (Sb2Se3) thin films were prepared by co-evaporation of Sb2Se3 and selenium (Se) sources on molybdenum (Mo)-coated soda lime glass. Solar cells were fabricated in the substrate configuration of Ag/ITO/ZnO/CdS/Sb2Se3/Mo/Glass. The [hk1] preferred orientation grain was found to be beneficial to higher performance solar cells because of its special one-dimensional crystal structure. Furthermore, a Mo selenization process prior to the Sb2Se3 deposition was introduced to improve the Sb2Se3/Mo interface. Material characterization and device physics analysis revealed that the formation of MoSe2 due to the Mo selenization enhanced the [221] orientation preference of the following Sb2Se3 and improved the quality of heterojunction, leading to a significant increase in open circuit voltage (VOC) and fill factor (FF). The champion solar cell showed a conversion efficiency of 4.25% with a VOC of 427 mV and a FF of 58.15%.

Reactively sputtered molybdenum trioxide (MoO3) thin films were systematically investigated and employed as cathodic electrochromic layers in all thin film electrochromic devices (ATF-ECDs). The gas loop controller was employed for adjustment of inputted oxygen gas flux by monitoring the target voltage during reactive sputtering. The working pressure played a great role on the deposition rate, crystallite size, optical properties and the electrochromic properties of MoO3 and the applied ATF-ECDs (soda lime glass (SLG)/ITO/NiOX/Ta2O5/MoO3/ITO). A 4 Pa MoO3 based ATF-ECD achieved a high optical modulation (transmission @ 600 nm) of ~50% and a high coloration efficiency of 149.4 cm2/C.

CdS QDs were successfully synthesized through a chemical reaction between cadmium acetate dehydrate and thioacetamide by using a microemulsion-mediated hydrothermal method. The properties of as-prepared CdS QDs can be controlled by using Emulsifier OP and CTAB surfactant, which produce a universal cubic phase and an unusual hexagonal phase, respectively. As a comparison, CdS QDs prepared by CTAB exhibit a better crystallinity and dispersibility. A possible mechanism involving the critical role of surfactant in the formation of crystal structure has also been explored in this paper. It is also found that the crystal size gradually increase with the increase of temperature, and the observation of red-shift in the absorption and emission peaks gives a clear evidence of the quantum confinement effect. All the desired properties of CdS QDs synthesized in this study imply the possibility of the preparation of high quality QDs under the appropriate reaction conditions.

Cu(In, Ga)Se2 (CIGS) thin films are deposited on flexible stainless steel (SS) substrates using the so called 3-stage co-evaporation process at different substrate temperatures ranging from 440 °C to 640 °C during the 2nd stage and the 3rd stage (TS2). The effects of TS2 on the properties of CIGS thin films are systematically investigated. It is found by secondary ion mass spectrometry measurement that CIGS thin films deposited at different TS2 show different Ga/(Ga + In) ratio (GGI) profiles along the growth direction. High TS2 facilitates the grain growth and leads to larger grain size. However, high TS2 worsens the spectral response of CIGS solar cells in the long wavelength range, which is partly attributed to the too much iron atom diffusion from the SS substrates into the CIGS thin films. All CIGS thin films show (112) preferred orientations with a shift to higher angle due to variation of compositions. A shoulder-like two-peak structure of (112) and (220/204) peaks appears for CIGS thin films deposited at lower TS2. Conversion efficiency of 11.3% is obtained for CIGS thin film solar cells deposited at the TS2 of 500 °C.