Efficient Heterojunction Solar Cells Research Articles

Two-dimensional quantum dots for highly efficient heterojunction solar cells

The electronic and optical properties of finite silicene, graphene, and arsenene heterostructures are investigated using first principles calculations. The optoelectronic properties of these structures are precisely controlled, by chemical functionalization, shape, and size, to produce suitable donor energy gap and minimal conduction band offset that enable the construction of efficient heterojunction solar cells. Heterojunctions with only Van der Waals interactions between layers have been achieved in functionalized silicene/graphene and arsenene/graphene. The distribution of the highest occupied/lowest unoccupied molecular orbital on donor/acceptor layer in addition to the contribution of each layer into the total electronic density of states insure that the only interlayer interaction is the van der Waals one and charge separation is attained. The heterojunctions have donors’ energy gaps ranging from 1.2 to 1.8 eV which in conjunction with the very low conduction band offset ∼ 0.002 eV enable the building of type-II solar cells with extremely high power conversion efficiency up to 23.34%. The prominent low energy optical excitations are mainly contributed by a transition from donor molecular orbitals to acceptor ones. Therefore, functionalized 2D heterojunctions are excellent candidates for building ultrathin, stable, and low-cost efficient solar cells.

Tandem photoelectrochemical and photoredox catalysis for efficient and selective aryl halides functionalization by solar energy

Tandem photoelectrochemical and photoredox catalysis for efficient and selective aryl halides functionalization by solar energy

Hybrid heterojunction solar cells based on single‐walled carbon nanotubes and amorphous silicon thin films

AbstractHybrid heterojunction solar cells based on silicon and single‐walled carbon nanotube (SWCNT) thin films have a simple structure and their manufacture employ simple low‐temperature processes. Moreover, their progress has been rapid during the last decade, wherein the efficiency of heterojunction solar cells combining hydrogenated amorphous silicon (a‐Si:H) and SWCNTs thin film has increased from 0.03% to 8.80%. Here, we present a comprehensive overview of the state‐of‐the‐art on SWCNTs/a‐Si:H heterojunction solar cells. In addition to a comprehensive technology review, important special features such as adhesion of SWCNT film to a‐Si:H, the interface between SWCNT and a‐Si:H, and their influence on the performance of the heterojunctions are included. Future paths for improving the performance of such solar cells are also suggested. Finally, key challenges and trends for further research and development of SWCNTs/amorphous silicon heterojunction solar cells are discussed.This article is categorized under: Photovoltaics > Science and Materials

Enhancing the photovoltaic performance of Cd-free Cu2ZnSnS4 heterojunction solar cells using SnS HTL and TiO2 ETL

Cu2ZnSnS4 chalcogenide semiconductor is a very promising absorber material for solar cells and no longer fulfilled its realistic goals due to the possible challenge of defect-free fabrication, non-optimized buffer layer alignment and device configuration. In this article, we proposed a new planner structure defined as (SnS/CZTS/TiO2/ITO) using Ni and Al as a back and front contact materials, respectively, and simulated its photovoltaic (PV) performance using SCAPS-1D. In the simulation, defect densities were added to each layer and the interface between the buffer layer and the absorber layer. This work demonstrated the promising role of SnS HTL and TiO2 ETL in reducing the Voc deficit of CZTS-based solar cells by forming more favourable band alignment with the absorber layer, reducing non-radiative recombination at the interfaces. In response to changes in the material properties of different layers (such as thickness, carrier concentration, defect density), working temperature, and back contact metal work function, the PV performance of the new architecture for CZTS solar cells was investigated and optimized. The study of PV performance optimization revealed that a relatively thicker absorber layer with low carrier concentration showed better PV performances, while ETL and HTL with a thinner and higher carrier concentration are required to enhance PV performances. Power conversion efficiency of >30%, Voc of >1.09 V, Jsc of >32 mA/cm2 and FF of >87% was predicted for CZTS solar cells with the new architecture. The findings of this study suggest that SnS and TiO2 are expected to become HTL and ETL, respectively, for fabricating low cost, high efficiency, and Cd-free CZTS-based heterojunction solar cell.

Influence of defects on silicon heterojunction solar cell efficiency: Physical model and comparison with data

We have studied the influence of defects on silicon heterojunction solar cell efficiency by a method based on the comparison of electroluminescence (EL) image data with a finite element circuit model of solar cell efficiency. For this purpose, a general curve that relates the solar cell efficiency to a parameter representative of the defect strength, i.e., the loss of VOC, ∆VOC, from EL maps is obtained, and it is shown that the efficiency can be predicted with a good degree of confidence.

Complex Investigation of High Efficiency and Reliable Heterojunction Solar Cell Based on an Improved Cu2O Absorber Layer

This study is aimed at increasing the performance and reliability of silicon-based heterojunction solar cells with advanced methods. This is achieved by a numerical electro-optical modeling and reliability analysis for such solar cells correlated with experimental analysis of the Cu2O absorber layer. It yields the optimization of a silicon tandem heterojunction solar cell based on a ZnO/Cu2O subcell and a c-Si bottom subcell using electro-optical numerical modeling. The buffer layer affinity and mobility together with a low conduction band offset for the heterojunction are discussed, as well as spectral properties of the device model. Experimental research of N-doped Cu2O thin films was dedicated to two main activities: (1) fabrication of specific samples by DC magnetron sputtering and (2) detailed characterization of the analyzed samples. This last investigation was based on advanced techniques: morphological (scanning electron microscopy—SEM and atomic force microscopy—AFM), structural (X-ray diffraction—XRD), and optical (spectroscopic ellipsometry—SE and Fourier-transform infrared spectroscopy—FTIR). This approach qualified the heterojunction solar cell based on cuprous oxide with nitrogen as an attractive candidate for high-performance solar devices. A reliability analysis based on Weibull statistical distribution establishes the degradation degree and failure rate of the studied solar cells under stress and under standard conditions.

Phosphorus treatment to promote crystallinity of the microcrystalline silicon front contact layers for highly efficient heterojunction solar cells

The current loss is mainly due to the reflection and the parasitic absorption in the indium tin oxide (ITO) and amorphous silicon (a-Si:H) in the front side of silicon heterojunction (SHJ) solar cells. In this paper, we implemented n-type hydrogenated microcrystalline silicon oxide (n-μc-SiOx:H) as the front surface field (FSF) to improve the short-circuit current density (JSC) of SHJ solar cells. The advantage of employing n-μc-SiOx:H layer is due to its low optical absorption coefficient and tunable refractive index. However, the introduction of carbon dioxide increases light transmission but reduces the crystallinity of n-μc-SiOx:H layer. Meanwhile, inhibiting the incubation layer and increasing microcrystalline/amorphous mixture phase during the growth are critical to the solar cell performance. Therefore, we implemented a high phosphorus-doping seed layer to form a nucleation layer to improve the crystallinity of n-μc-SiOx:H layer. In addition, the plasma enhanced chemical vapor deposition (PECVD) process parameters of each layer were optimized to obtain good optical and electrical properties of n-μc-SiOx:H layer. Finally, a 242.5 cm2 solar cell had been fabricated with conversion efficiency of 23.87%, open-circuit voltage (VOC) of 739.8 mV, fill factor (FF) of 82.33% and JSC of 39.19 mA/cm2, which was 0.31 mA/cm2 higher than that of the conventional n type a-Si:H SHJ solar cells.

Enhancement of Organic Solar Cell Performance by Utilizing Cupper Phthalocyanine

An approach for improving the photoelectrical conversion efficiency of hetero-junction solar cells based on lead phthalocyanine, by incorporating cupper phthalocyanine with co-evaporation technique into the active layer has been reported in this work, the effect of adding cupper phthalocyanine (CuPc) have been studied. The morphological, optical, and electrical properties of PbPc active layer and blend have been reported. Atomic force microscope study shows a change in the roughness, UV-VIS Spectroscopy revealed that the absorbance of PbPc films increases in the blend case and has a main Q-band at wavelength 748 nm and the electrical study showed a change in (I–V) characteristics, the photoelectrical conversion efficiency (PCE) of solar cells increases. The photovoltaic parameters are discussed based on the morphology and optical variation of the active layers.

Review of the development of copper oxides with titanium dioxide thin-film solar cells

Copper oxide-titanium dioxide (TiO 2) p–n junctions are promising materials for photovoltaic devices and may reduce production costs due to their low cost and inexpensive production methods compared with silicon solar cells. The present review compares solar cells made with copper oxides combined with TiO 2–TiO 2/Cu 2O and TiO 2/CuO heterojunctions, and “cascade heterojunction systems.” First, we describe the main properties of titanium (iv) dioxide (TiO 2), cuprous oxide (Cu 2O), and cupric oxide (CuO), and their potential applications. Next, we explain the concept of copper oxide and TiO 2 heterojunctions. We summarize and present the photovoltaic characteristics (efficiency, fill factor, circuit current density, and open circuit voltage), thickness, preparation method, and electrode type for solar cells comprising copper oxide and TiO 2. The efficiency of the solar cells ranged from 0.0005% to 1.62%. The thickness of the TiO 2 and cupric oxide layers ranged from 0.06 to 16 µm, and from 0.18 to 1.5 µm, respectively, depending on the fabrication method. Additionally, we review and discuss the available combinations of copper oxide with other materials (Cu 2O with ZnO, CuO with ZnO, and CuO with Si), as well as the effect of the thickness of the copper (i) oxide and copper (ii) oxide on the solar cell performance. Finally, we present aspects to improve the conversion efficiency of heterojunction solar cells with copper oxides combined with TiO 2. This review will be useful for the construction and further development of thin-film solar cells.

Highly efficient heterojunction solar cells enabled by edge-modified tellurene nanoribbons.

Tellurene, a two-dimensional (2D) semiconductor, meets the requirements for optoelectronic applications with desirable properties, such as a suitable band gap, high carrier mobility, strong visible light absorption and high air stability. Here, we demonstrate that the band engineering of zigzag tellurene nanoribbons (ZTNRs) via edge-modification can be used to construct highly efficient heterojunction solar cells by using first-principles density functional theory (DFT) calculations. We find that edge-modification enhances the stability of ZTNRs and halogen-modified ZTNRs showing suitable band gaps (1.35-1.53 eV) for sunlight absorption. Furthermore, the band gaps of ZTNRs with tetragonal edges do not strongly depend on the edge-modification and ribbon width, which is conducive to experimental realization. The heterojunctions constructed by halogen-modified ZTNRs show desirable type 2 band alignments and small band offsets with reduced band gaps and enhanced sunlight absorption, resulting in high power conversion efficiency (PCE) in heterojunction solar cells. In particular, the calculated maximum PCE of designed heterojunction solar cells based on halogen-modified ZTNRs can reach as high as 22.6%.

Limiting Efficiency of Heterojunction Solar Cells

A heterojunction solar cell consists of a p-n junction between a high-bandgap and a low-bandgap semiconductor. As the cell is made up of two different semiconductors, the fundamental question that arises is whether the limiting efficiency of the heterojunction solar cell is determined by the low-bandgap semiconductor, the high-bandgap semiconductor, some value in-between or, perhaps, even some other value exceeding the limiting efficiency of single gap solar cells. In this respect, in this paper, we demonstrate that the limiting efficiency lies in-between, without the absolute limiting efficiency of single gap solar cells being exceeded. However, in spite of this result, we find that the open-circuit voltage of heterojunction solar cells can exceed the bandgap (divided by the electron charge) of the low-bandgap semiconductor, something that is not possible in single gap solar cells.

Development of Heterojunction Solar Cells Comprising of Boron-Doped Silicon-Carbon Based Semiconductor Thin Films and n-Si

1. Introduction Multi-layered structure is one of the methods to enhance the photoelectric conversion efficiency of solar cells. The optical gap of amorphous silicon carbide (a-SixC1-x) semiconductor thin films can be controlled by changing the ratio of silicon and carbon atoms. Moreover, a-SixC1-x thin films can easily form the stacked cell compared to single-crystalline and polycrystalline materials because clean lattice constant cannot be defined. Therefore, a-SixC1-x thin film is a promising material that enables us to realize the multi-junction solar cells with high-efficiency. Our research group has reported the fabrication of a-SixC1-x semiconductor thin films with controllable optical gap in the range from 1.25 to 2.76 eV [1]. However, the conversion efficiency of heterojunction solar cell comprised of p-type a-SixC1-x thin film and n-Si substrate was approximately 2.7×10-4 %. The reason of this small value might be the formation of defects such as dangling bond at interface between p-type a-SixC1-x film and n-Si substrate because high power is needed for the decomposition of source gases in the deposition [3]. In this study, the damage of junction interface was decreased by decreasing power of applied radio-frequency input. Furthermore, the decomposition rate of source gases was tried to be enhanced by increasing frequency to improve the performance of solar cells. 2. Experimental The heterojunction solar cells comprising boron-doped a-SixC1-x thin film and n-Si substrate were fabricated by plasma-enhanced chemical vapor deposition (SAMCO, BPD-1) equipped with variable-frequency radio frequency generator (THAMWAY, T162-5767C) using trimethylsilane and trimethylborate as source materials. B/(Si + C) ratio in the liquid source was 7.50 at.%. The boron-doped a-SixC1-x thin films were deposited by changing discharge frequency and applied power. The substrate temperature and deposition time were adjusted to 200˚C and 20 min, respectively. The performance of heterojunction solar cells was investigated by current-voltage (I-V) measurement (KEYSIGHT, B2901A) with simulated AM 1.5 sunlight (ASAHI SPECTRA, HAL-320). In addition, in order to evaluate the quality of pn junction, the junction capacitance was calculated from AC impedance measurement (Solartron Analytical, SI 1260 and 1287). 3. Results and discussion As described in the previous paper, the conversion efficiency of heterojunction solar cell prepared at frequency of 40.68 MHz and power of 100 W was 2.7×10-4 % [2]. The conversion efficiency was increased to 1.83×10-2 % by decreasing power from 100 to 10 W. Moreover, the efficiency was increased to 3.03×10-1 % with increasing frequency from 40.68 to 60.00 MHz. Figure 1 shows I-V characteristics of solar cells fabricated at 40.68 and 60.00 MHz under simulated sunlight irradiation. As a result of increase frequency, short-circuit current density and open-circuit voltage, which are contributed to the conversion efficiency, were drastically increased. Figure 2 shows capacitance-voltage (C-V) characteristics of heterojunction solar cells fabricated at 40.68 and 60.00 MHz. The capacitance of solar cells prepared at 40.68 and 60.00 MHz were 2.61 and 3.12 nF/cm2 (at zero bias), respectively. It has been reported that the bombardment energy of ion in plasma is decreased by increasing frequency [4]. Therefore, we consider that the capacitance is increased, since the defect at interface might be decreased with increasing frequency. From 1/C2-V plot, the slope of solar cell prepared at 60.00 MHz was smaller than that of solar cell prepared at 40.68 MHz. This result implies that the carrier density of boron-doped a-SixC1-x thin film deposited at 60.00 MHz is larger than that of the thin film deposited at 40.68 MHz. This might be because the decomposition rate of source gases might be enhanced by increasing frequency. From these results, the conversion efficiency of boron-doped a-SixC1-x/n-Si heterojunction solar cell was successfully enhanced by the improvement of junction quality and increasing carrier density.

Highly efficient and stable planar heterojunction solar cell based on sputtered and post-selenized Sb2Se3 thin film

Antimony selenide (Sb2Se3) is regarded as one of the key alternative absorber materials for conventional thin film solar cells due to its excellent optical and electrical properties. Here, we proposed a Sb2Se3 thin film solar cell fabricated using a two-step process magnetron sputtering followed by a post-selenization treatment, which enabled us to optimize the best quality of both the Sb2Se3 thin film and the Sb2Se3/CdS heterojunction interface. By tuning the selenization parameters, a Sb2Se3 thin film solar cell with high efficiency of 6.06% was achieved, the highest reported power conversion efficiency of sputtered Sb2Se3 planar heterojunction solar cells. Moreover, our device presented an outstanding open circuit voltage (VOC) of 494 mV which is superior to those reported Sb2Se3 solar cells. State and density of defects showed that proper selenization temperature could effectively passivate deep defects for the films and thus improve the device performance.

Side chain triphenylamine-based conjugated polymers for the preparation of efficient heterojunction solar cells

A series of novel benzothiadiazole based triphenylamine polymers containing different electron-rich side chains (dithienosilole, dithienopyrrole, dithieno-cyclopentadiene derivatives) have been prepared and their photoelectric properties explored. These polymers have been characterized using UV–Vis absorption and fluorescence spectroscopy and their photo-electrochemical properties characterized using cyclic voltammetry. These new polymers exhibit high thermal decomposition temperatures and broad absorption spectra that enable them to absorb light across the entire visible region. The UV absorption response range electron of these polymers could be tuned by modifying their electron donating units, with the best polymer found to exhibit a long fluorescent lifetime. An P3:PC71BM device containing dithienocyclopentadiene electron donating side-chains was shown to give 3.6% photoelectric conversion efficiency for a high short-circuit current of 14.25 mA/cm2. The fluorescence intensity of this copolymer decayed rapidly, implying that effective charge transfer processes were occurring at its interface, which were associated with a relatively high short circuit current. This work clearly demonstrates that use of an appropriate electron donor unit can effectively broaden the polymers spectroscopic response range, thus increasing the rate of carrier transport at the interface, which leads to improved photoelectric conversion efficiency.

Efficient heterojunction solar cells based on the synergy between planarity and dipole moment in fluorinated-thienothiophenes-based donor-acceptor polymers

Polymers consisting of benzodithiophene, dithienopyrrole derivative donor monomers and thiophene derivative acceptor units are synthesized. The effects of F on optical performance for several Donor-Acceptor conjugated polymer systems are investigated. The introduction of F is conducive to increasing the dipole moment of the molecule for effective intramolecular charge transmission. The incorporation of F in acceptor unit improves molecular planarity simultaneously. It is found that dipole moment and molecular planarity play a synergistic role in photovoltaic performance. Under the premise of ensuring the planarity, the dipole moment is enhanced, the charge transfer within the molecule can also be strengthened, thus, the short-circuit current is greatly increased. The theoretical calculations show and explain the effect of the F on the dipole moment. Finally, a PCE of 4% is achieved with a large short-circuit current density of 14.36 mA cm−2. These results represent a synergy between planarity and dipole moment for improving the PCE.

Broadband antireflection property of conformally grown zinc tin oxide thin films on nanorippled- and nanofaceted-Si substrates

In this paper, we show the broadband antireflection property of radio frequency sputter-grown zinc tin oxide (ZTO) thin films grown on ion-beam fabricated self-organized nanoscale rippled- (R-Si) and faceted-Si (F-Si) substrates. For the sake of comparison, ZTO film has been deposited simultaneously on pristine-Si (P-Si) substrate as well. X-ray diffraction studies show the amorphous nature of the films. Atomic force microscopic studies reveal the conformal growth of ZTO thin films (granular in nature) on both R- and F-Si substrates (up to 60 nm). Surface reflectance measurements show a large reduction in the average broadband (300–800 nm) surface reflectance (at 550 nm) from 43.9% for P-Si substrate to 42% and 32% for R-Si and F-Si substrate, respectively. In addition, we show a further reduction in the surface reflectance following the growth of ZTO overlayers (in the range of 15–60 nm) on P-Si, R-Si, and F-Si substrates. As a matter of fact, there is a continuous reduction in surface reflectance up to a thickness of 60 nm, beyond which the reflectance minimum starts increasing. The large reduction in the surface reflectance of ZTO coated P-, R-, and F-Si substrates are attributed to the graded refractive index of the heterostructures driven by the surface morphology of the substrates and the different average surface heights of the films. This study will be very useful for efficient ZTO-based optoelectronic devices and heterojunction solar cell applications.

Highly flattened donor-acceptor polymers based on fluoride-substituent acceptors for efficient heterojunction solar cells

For high performance polymer solar cells, the effects of planarity and alkyl chain steric hindrance are systematically examined in the polymer poly[1-(4-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-6-methylbenzo[1,2-b:4,5-b′]dithiophen-2-yl)-6-methylthieno[3,4-b]thiophen-2-yl)-2-ethylhexan-1-one] (P4) constructed with a benzo[1,2-b:4,5-b′] dithiophene (BDT) plane with symmetrical thiophene side chains, poly[2-ethyl-1-(6-methyl-4-(6-methyl-4,4-dioctyl-4H-silolo[3,2-b:4,5-b′]dithiophen-2-yl)thieno[3,4-b]thiophen-2-yl)hexan-1-one] (P5), composed of silaindacenodithiophene, poly[2-ethyl-1- (6-methyl-4-(6-methyl-4-octyl-4H-dithieno[3,2-b:2′,3′-d]pyrrol-2-yl)thieno[3,4-b]thiophen-2-yl)hexan-1-one] (P6), based on pyrrole moieties and the corresponding F-containing polymers, poly[1-(4-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-6-methylbenzo[1,2-b:4,5-b′]dithiophen-2-yl)-3-fluoro-6-methylthieno[3,4-b]thiophen-2-yl)-2-ethylhexan-1-one] (P1), Poly[2-ethyl-1-(3-fluoro-6-methyl-4-(6-methyl-4,4-dioctyl-4H-silolo[3,2-b:4,5-b′]dithiophen-2-yl)thieno[3,4-b]thiophen-2-yl)hexan-1-one] (P2), and Poly[2-ethyl-1-(3-fluoro-6-methyl-4-(6-methyl-4-octyl-4H-dithieno[3,2-b:2′,3′-d]pyrrol-2-yl)thieno[3,4-b]thiophen-2-yl)hexan-1-one] (P3). Except for P1 and P4, the alkyl chain is directly linked to the main chain in the polymers. P1 has a high degree of flatness because flanking thienyls can decrease the torsion angle between conjugated units. In addition, the introduction of fluorine (F) on the thienothiophene acceptors of P4 reduces the dihedral angle between the BDT and thienothiophene, resulting in a more planar P1. Moreover, the introduction of short alkyl and thiophene side chains minimizes the intermolecular steric hindrance of P1 and ensures strong inter-chain aggregation and π-π stacking. However, the introduction of F in P2 and P3 increases the dihedral angle relative to non-F-containing P5 and P6. Finally, an efficiency of 7.1% is obtained for P1, leading to a 50% increase in power conversion efficiency (PCE) compared with P4. This work is a step towards enhanced polymer planarity and minimal intermolecular steric hindrance for the development of efficient polymer heterojunction solar cells.

Light intensity dependent characteristics of micro-textured Si/PEDOT:PSS heterojunction solar cell

Heterojunction solar cells made of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and Si have attracted a lot of attention towards low-cost and efficient devices. Here, heterojunction solar cell using pristine PEDOT:PSS on micro-textured n-Si has been fabricated. Effect of light intensity on photovoltaic characteristics of PEDOT:PSS/Si cells has been investigated via current (J) versus voltage (V) characteristics and quantum efficiency (EQE) measurements. It is found that photocurrent (Jsc) of such cells deteriorates drastically at higher light intensities resulting in quite low Jsc (~ 15.0 mA/cm2) in J–V response under intense white light than that obtained from EQE measurements (> 30.0 mA/cm2) under low intensity monochromatic light. The observed effect of light intensity on the cell performances is reversible. Structural stability of PEDOT:PSS layer is also investigated by Raman spectroscopy. No post high intensity light exposure structural transformation in the PEDOT:PSS layer is observed. The observed light sensitive photoresponse of such cells has been attributed to possible light induced instantaneous structural changes in the PEDOT:PSS layer leading to reduced charge carrier dynamics and hence the formation of space charge region at PEDOT:PSS/Si interface at higher intensities. Further, the EQE with varying intensity is done which can help to optimize the illumination condition for such cell. The present study opens up new area of intensive research required in order to optimize polymer layer properties and improving the performance of PEDOT:PSS/Si solar cell leading to efficient, stable and low cost heterojunction solar cell technology.

Highly Efficient Photocatalytic Water Splitting over Edge-Modified Phosphorene Nanoribbons.

Two-dimensional phosphorene with desirable optoelectronic properties (ideal band gap, high carrier mobility, and strong visible light absorption) is a promising metal-free photocatalyst for water splitting. However, the band edge positions of the valence band maximum (VBM) and conduction band maximum (CBM) of phosphorene are higher than the redox potentials in photocatalytic water splitting reactions. Thus, phosphorene can only be used as the photocathode for hydrogen evolution reaction as a low-efficiency visible-light-driven photocatalyst for hydrogen production in solar water splitting cells. Here, we propose a new mechanism to improve the photocatalytic efficiency of phosphorene nanoribbons (PNRs) by modifying their edges for full reactions in photocatalytic water splitting. By employing first-principles density functional theory calculations, we find that pseudohalogen (CN and OCN) passivated PNRs not only show desired VBM and CBM band edge positions induced by edge electric dipole layer, but also possess intrinsic optoelectronic properties of phosphorene, for both water oxidation and hydrogen reduction in photocatalytic water splitting without using extra energy. Furthermore, our calculations also predict that the maximum energy conversion efficiency of heterojunction solar cells consisting of different edge-modified PNRs can be as high as 20% for photocatalytic water splitting.

Improved Reproducibility and Intercalation Control of Efficient Planar Inorganic Perovskite Solar Cells by Simple Alternate Vacuum Deposition of PbI2 and CsI.

Vacuum deposition is a simple and controllable approach that aims to form higher-quality perovskite films compared with those formed using solution-based deposition processes. Herein, we demonstrate a novel method to promote the intercalation control of inorganic cesium lead iodide (CsPbI3) perovskite thin films via alternate vacuum deposition. We also investigated the effect of layer-by-layer deposition of PbI2/CsI to fabricate efficient planar heterojunction CsPbI3 thin films and solar cells. This procedure is comparatively simple when compared with commonly used coevaporation techniques; further, precise intercalation control of the CsPbI3 thin films can be achieved by increasing the number of layers in the layer-by-layer deposition of PbI2/CsI. The best control and the highest reproducibility were achieved for the deposition of four double layers owing to the precise intercalation control during the deposition of the CsPbI3 thin film. A power conversion efficiency of 6.79% was obtained via alternating vacuum deposition of two double layers with a short-circuit current density (Jsc) of 12.06 mA/cm2, an open-circuit voltage (Voc) of 0.79 V, and a fill factor (FF) of 0.72. Our results suggest a route for inorganic precursors to be used for efficient perovskite solar cells via alternating vacuum deposition.