Lead free CsSn0.5Ge0.5I3 perovskite solar cell with different layer properties via SCAPS-1D simulation

Organic–inorganic halide perovskite solar cells (PSCs) have been extensively studied due to their simple fabrication methods and obvious device efficiency advantages. In this work, the perovskite CsSn_0.5Ge_0.5I₃ is used as the light absorption layer, which is doped with Ge²⁺ in CsSnI₃ to improve its stability. The polymers of 3-hexylthiophene (P3HT) with excellent optoelectronic properties and low price, and SnO₂ with high electron extraction ability is selected as charge transport layers. Based on these, a novel PSC structure (FTO/SnO₂/IDL1/CsSn_0.5Ge_0.5I₃/IDL2/P3HT/Au) has been simulated via solar cell capacitor simulator (SCAPS-1D). The PSC performance is optimized by adjusting a series of parameters, including the layer thickness, defect density, electron affinity potential energy, and operating temperature, and so forth. The results show that the PSC defects are passivated by adjusting the appropriate parameters, and the final optimized open circuit voltage (V_OC) is 1.08 V, short-circuit current density (J_SC) is 27.37 mA/cm², fill factor (FF) is 83.32%, while the power conversion efficiency (PCE) is increased from the initial 10.89% to 24.63%, which provides theoretical reference for experiments and new ideas for the preparation and development of efficient and environmentally friendly PSCs. Finally, the effect of different metal cathodes with and without hole transport layer (HTL) on PSC performance is compared. The PSCs without HTL are more dependent on battery cathodes, which provided a way to replace precious metals with other electrode materials.     

Optimization of TiO2 paste concentration employed as electron transport layers in fully ambient air processed perovskite solar cells with a low-cost architecture

The optimization of thickness and surface roughness of the TiO₂ layer as an efficient electron transporting layer (ETL) plays a significant role on the performance improvement of perovskite solar cells (PSCs). In the present investigation, TiO₂ pastes synthesized with various concentrations under hydrothermal conditions were utilized to deposit the TiO₂ films of tunable porosities as the ETLs of PSCs. Also, the PSCs were fabricated with a structure of FTO/block-TiO₂ (b-TiO₂)/m-TiO₂/CH₃NH₃PbI₃ (MAPbI₃)/CuInS₂ (CIS)/carbon as a low-cost architecture. Moreover, the effect of the TiO₂ paste concentration was studied on the performances of PSCs under fully ambient conditions. The optimal TiO₂ layer was constructed with 20 wt% TiO₂ paste concentration, which resulted in the formation of a hole‐free, smooth, and compact ETL layer. The champion perovskite solar cell fabricated with the 20 wt% TiO₂ paste concentration showed the highest power conversion efficiency (PCE) of 13.09% (J_SC = 20.80 mA cm^?2, V_OC = 0.98 V and FF = 0.64) but the champion PSC device made with the 10 wt% TiO₂ paste exhibited the lowest PCE = 8.05% (J_SC = 19.83 mA cm^?2, V_OC = 0.91 V and FF = 0.45). These results illustrated that the optimal 20 wt% TiO₂ paste caused ～163% enhancement in the PCE of the device. Consequently, it could be suggested for application in fabrication of cost-effective and large scale PSCs.     

A thioacetamide interlayer anchoring TiO2 and (FAPbI3)1−x(MAPbBr3)x for high-performance perovskite solar cells

In the perovskite solar cells (PSCs), traps of the perovskite film or interface are the research focus, which can severely hinder charge transfer and benefit charge recombination, thus weakening the photoelectric performance of the devices. Herein, a Thioacetamide (TAA) interfacial layer is used to passivate the traps of PSCs. Comparing to the control device (17.65%), the TAA-based solar cells can achieve an enhanced efficiency of 19.14%. It is found that the passivation caused by TAA occurs through the interactions of sulfur in TAA with undersaturated Pb in perovskite and Ti⁴⁺ in TiO₂, resulting in a faster and more efficient charge transfer and a greatly reduced trap density from 3.36 × 10¹⁶ cm⁻³ to 1.93 × 10¹⁶ cm⁻³. It is shown that the modification method using TAA may be helpful for passivating traps and obtaining excellent photoelectric properties of PSCs.     

Nanostructured bilayer CuSCN@CuI thin films as efficient inorganic hole transport material for inverted perovskite solar cells

In this work, the development of bilayer CuSCN@CuI inorganic hole transport material by a simple electrochemical approach is demonstrated. The thickness and the morphology of the bilayer thin films are controlled by electrochemical potential and deposition time. Uniformly distributed triangle-shaped CuI nanosheets formation is observed at 2 min deposition time. Inverted perovskite solar cells are fabricated using electrochemically grown CuSCN@CuI bilayer and tested its photovoltaic performance. The maximum short circuit current density of 18.24 mA/cm² and open-circuit voltage of 1080 mV is achieved for uniformly distributed triangle-shaped CuI nanosheets grown at 2 min deposition time. The power conversion efficiency (PCE) of 15.58% is achieved with 1400 h of stability. The moderate thickness (~180–230 nm) of bilayer CuSCN@CuI nanostructures showed better charge transport and photovoltaic performance. The favourable band alignment of the designed CuSCN@CuI/perovskite/PC₆₁BM/Carbon delivers stable open-circuit voltage than the earlier reports. The optimized bilayer CuSCN@CuI nanostructure with carbon back contact showed improved device stability.     

Using water‐soluble nickel acetate as hole collection layer for stable polymer solar cells

We report polymer solar cells (PSCs) based on poly(3‐hexylthiophene (P3HT) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) using water‐soluble nickel acetate (Ni(CH₃COO)₂, NiAc) instead of acidic poly(3,4‐ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT : PSS) as hole collection layer (HCL) between the indium tin oxide (ITO) electrode and photoactive layer. The NiAc layer can effectively decrease R_s and increase R_p and shows effective hole collection property. Under the illumination of AM1.5G, 100 mW/cm², the short‐circuit current density (J_sc) of the NiAc based device (ITO/NiAc/P3HT : PCBM/Ca/Al) reach 11.36 mA/cm², which is increased by 11% in comparison with that (10.19 mA/cm²) of PEDOT : PSS based device (ITO/PEDOT : PSS/P3HT : PCBM/Ca/Al). The power conversion efficiency of the NiAc based devices reach 3.76%, which is comparable to that (3.77%) of the device with PEDOT : PSS HCL under the same experimental conditions. Moreover, NiAc based PSCs show superior long‐term stability than PEDOT : PSS based PSCs. Our work gives a new option for HCL selection in designing more stable PSCs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyaniline polymer-modified ZnO electron transport material for high-performance planar perovskite solar cells

In this study, an efficient strategy is used to prepare perovskite photoactive layer with superb optoelectronic merits by utilizing polyaniline polymer as an efficient additive to improve perovskite quality. As a result, we prove that the small content of polyaniline (PANI) provides not only suppresses the perovskite defects and lead iodide but also produces a passivation impact. By regarding using macromolecular phases with long chain polymers, the generation of a PANI-perovskite cross-linking is possible. The cross-linking acts to bridge the perovskite crystals, mitigating carrier trapping by grain boundaries and achieving remarkable air stability against humid, which has not been obtainable with tiny molecules defect passivating materials. Also, PANI promoted the development of Lewis base adduct with the perovskite precursor, which, maximized the activation energy for nucleation and growth of the perovskite phase. Therefore, the perovskite layer with optimized PANI additive showed higher crystallinity in (110) crystal plane. After PANI addition, the perovskite grains found to be enlarged from 350 nm to 620 nm. Also, the PSCs with PANI showed suppressed luminescence effect, which indicates lower recombination rates. The SCLC measurements revealed that the PANI additive improving the interfacial contact between the ZnO and perovskite due to reduction the trapped density from 1.78 × 10¹⁶ cm^-3 to 2.46 × 10¹⁵. Consequently, the champion cell yields an efficiency of 17.39% for 4% polyaniline doped electron transport material with negligible hysteresis. This reduces PSC instability generating a device that retained 93% of its original performance after 600 h maintaining in air conditions without any encapsulation.     

Taguchi optimization of device parameters for fullerene and Poly (3-octylthiophene) based heterojunction photovoltaic devices

Photovoltaic devices were fabricated with the structure ITO/fullerene/Poly (3-octylthiophene)/Au and device parameters were optimized using Taguchi optimization technique. Optimized parameter such as fullerene and Poly (3-octylthiophene) film thickness, annealing temperature and annealing duration are found to be as 110 nm, 45 nm, 120° C and 15 min respectively. Fabricated device with optimized parameters shows short circuit current density (J_sc), open circuit voltage (V_oc) and fill factor (FF) as 2 × 10^− 4 mA/cm², 0.47 V and 0.25 respectively. Effect of solvent casting on C₆₀ layer was studied which shows formation of uneven surface providing large interfacial area.     

Novel wide band-gap polymer utilizing fused hetero-aromatic unit for efficient polymer solar cells and field-effect transistors

Novel wide band-gap polymer of PBTFT containing dibenzosexithiophene-alt-bithiophene backbone was designed and synthesized via the Stille cross-coupling reaction. This polymer exhibited good thermal stability, well coplanar backbone and a broad absorption band from 350 nm to 610 nm with a wide optical band-gap of 2.02 eV. The polymer solar cells (PSCs) based on the PBTFT:PC₇₁BM active layer showed the power conversion efficiency of 3.0% with an open circuit voltage of 0.70 V, a short-circuit current of 7.94 mA cm⁻² and a fill factor of 53.98% under the illumination of AM.1.5, 100 mW cm⁻². Holes mobility up to 0.028 cm² V⁻¹ s⁻¹ with an on-off ratio of 1.0 × 10⁶ was obtained in the PBTFT-based organic field-effect transistors (OFETs). Our work indicates that the dibenzosexithiophene-alt-bithiophene based copolymer can be efficiently applied in PSCs and OFETs.     

Solution-processed nickel oxide hole transport layer for highly efficient perovskite-based photovoltaics

Solution processed NiO_x is one of the promising hole transport layer (HTL) for planar perovskite solar cells, which can replace hygroscopic poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) HTL. In this study, we investigated effects of ethylenediamine (EDA) additive in NiO_x precursor solution (nickel nitrate hexahydrate dissolved in ethyleneglycol) on optoelectronic and surface morphological properties of resultant solution processed NiO_x films. By varying EDA content (0–10.0?v/v %) in the precursor, we could find out that adequate EDA additive (~5.0%) provide much reduced electrical resistivity and enhanced optical transmission compared with control NiO_x film (No EDA) by suppressing formation of byproducts (i.e. nickel hydroxide). In addition, AFM surface topography showed much compact and dense deposition of NiO_x film on ITO electrode. This contributed to improve charge transport properties and suppress charge recombination loss at ITO/perovskite interface, which provided strong enhancement in fill factor from 0.599 to 0.714 in the perovskite solar cells. As a result, a power conversion efficiency (PCE) was strongly increased from 13.9 (No EDA) to 16.7% (EDA 5.0%). This also outperformed the performance (14.3%) of device using PEDOT: PSS, which indicates that the adequate control of EDA additive for NiO_x HTL could offer much promising photovoltaic performance.     

Tetramethylammonium based lead free perovskite active layer for solar cell application

Here we report the synthesis of a novel lead free organic-inorganic halide perovskite layer, tetramethylammonium tin tri-iodide (TMASnI₃), by simple and cost-effective chemical synthesis technique. The microstructural and optical studies confirm the formation of hexagonal perovskite structure with optical band gap ∼2.44 eV. A solar cell structure is fabricated by depositing the perovskite layer on zinc oxide thin film to demonstrate stable photovoltaic response under solar spectrum, where a thin layer of graphene oxide flakes on top of the perovskite layer acts as the charge transport layer. The open-circuit voltage (V_oc) and short circuit current density (J_sc) for this cell as extracted from the current-voltage measurement under one sun illumination of AM1.5 solar radiation are 0.60 V and 8.65 mA/cm², respectively. Without using any conventional hole transport layer, the power conversion efficiency (η) has been obtained as 1.92% which indicates the suitability of this perovskite material as an active layer for perovskite solar cell.     

Spray-deposited kesterite Cu2ZnSnS4 (CZTS): Optical,structural, and electrical investigations for solar cell applications

Kesterite Cu₂ZnSnS₄ (CZTS)-based solar devices have become a popular alternative to copper indium gallium selenide (CIGS) due to its outstanding properties such as high efficiency, non-toxicity, cost-effectiveness, suitable optoelectrical properties, and earth-abundancy. In this study, we directly fabricated CZTS films via a single-step spray pyrolysis technique, in contrast to conventional techniques where post sulfurization is required. The spray deposited CZTS films are investigated for their optical, structural, and electrical properties. The X-ray diffraction (XRD) and Raman analysis study revealed the synthesis of the phase-pure kesterite CZTS films without impurity phases. Large crystallites of CZTS are obtained at a deposition temperature of 400 °C, exhibiting a porous granular morphology with different grain sizes upon temperature variation. The size-dependent optical properties revealed that the CZTS films exhibited admirable visible light absorption of 10⁵ cm^?1 and an electronic bandgap ranging between 1.42 and 1.58 eV. The minimum dielectric loss obtained for optimized CZTS due to fewer intrinsic defects confirmed the materials’ applicability. Thus, the study provides a simple, viable route to fabricate CZTS without post-treatment to build affordable solar cells.     

Hole-limiting conductive vinyl copolymers for AlQ3-based OLED applications

A series of soluble conductive vinyl copolymers containing a hole-transporting N-(4-methoxyphenyl)-N-phenylnaphthalen-1-amine (MeONPA) moiety and an electron-transporting/hole-blocking 2,5-diphenyl-1,3,4-oxadiazole (OXA) moiety at different composition ratios were synthesized and characterized. The copolymers were applied as the hole-transporting layer (HTL) for a series of heterojunction Organic Light-emitting Diodes (OLEDs) employing the commonly used green emitter tris(8-hydroxyquinolinato)aluminum (AlQ₃) as the electron-transporting layer. AlQ₃ is known to have inferior electron mobility compared to most typical hole-transporting materials. As a result, oxidative degradation of the AlQ₃ emitters caused by the excessive holes accumulated at the interface led to deterioration of the device over time. From the measurement of hole current only devices using electron blocking gold as cathode (ITO/PEDOT:PSS/copolymer/Au), it was found that the hole current for the copolymers reduced as the OXA composition increased. Optimum performance for the AlQ₃-based OLED (ITO/PEDOT:PSS/copolymer/AlQ₃/Ca/Al) was achieved for a 82/18 (molar ratio) (MeONPA/OXA) copolymer. The maximum current efficiency and luminance were 4.2 cd/A and ca 24,000 cd/m² respectively for the charge-balanced copolymer compared to 3.5 cd/A and 6600 cd/m² for similar device employing a homopolymer P(MeONPA) as the HTL.     

Ultra-low core loss FeSiAl-based soft magnetic composites with ultra-thin MoO3 composite insulating layer

In this work, core/shell structured FeSiAl/MoO₃ (spherical FeSiAl covered by ultra-thin MoO₃ composite insulating layer) soft magnetic composites (SMCs) have been fabricated by a two-step heat treatment process. The influences of ammonium molybdate (AHM) content, first-step annealing temperature and second-step annealing temperature on magnetic, mechanical properties and electrical resistivity (ρ) have been comprehensively investigated. It is shown that the coating integrity and the thickness of MoO₃ nanoparticles layer can be regulated by the content of AHM, leading to the improvement of ρ. Moreover, composite insulating layer with the thickness of 47 ± 8 nm is formed and completely coated on FeSiAl particles with 15 wt% AHM, resulting in the fact that the highest radial crushing strength (K = 62.3 MPa) and lowest core loss (P_cv = 128.8 mW/cm³) is obtained. In addition, P_cv is separated into two components: hysteresis loss component and eddy current loss component. Further studies display that eddy current loss is only half of hysteresis loss. As a result, the FeSiAl SMCs with 47 ± 8 nm MoO₃ composite insulating layer possess the lowest core loss of 128.8 mW/cm³ at 50 mT/100 kHz. The low core loss of the FeSiAl/MoO₃ SMCs with ultra-thin composite insulating layer has a great potential in the fields of conversion and power transmission.     

Air fabrication of SnO2 based planar perovskite solar cells with an efficiency approaching 20%: Synergistic passivation of multi-defects by choline chloride

Defects in the perovskite films impose a serious issue on the PCE and stability of the SnO₂ based planar perovskite solar cells (SP–PSCs). So far, most researches have focused on regulating the SnO₂/perovskite interface to improve performance. However, defect passivation of the perovskite/HTM interface is more significant and potential. Herein, the non-toxic and cheap choline chloride was performed to passivate multiple defects of the MAPbI₃/HTM interface in ambient atmosphere. An optimal PCE of 19.93% (the average PCE was 18.60%) was obtained for the passivated device. Furthermore, the effect and mechanism of choline chloride on the humid and thermal stability of the SP-PSCs was investigated in detail. The passivated device without encapsulation retained 91% of its initial efficiency after 20 days in humid environment (20 ± 5 °C, 55 ± 5% RH) and 95% of the initial value under heating for 7 cycles (85 °C). Chloride ions with smaller radius and larger electronegativity formed stronger ionic bonding with Pb²⁺ to passivate I^? vacancy defects, while choline ions passivated MA⁺ vacancies. This work not only provides guidance for fabrication of an efficient and stable device in air, but also opens an avenue to understanding of relation between stability and defects in the SP-PSCs.     

A Promising Modified SILAR Sequence for the Synthesis of Photoelectrochemically Active Cu2ZnSnS4 (CZTS) Thin Films

A promising modified SILAR sequence approach has been employed for the synthesis of photoelectrochemically active Cu₂ZnSnS₄ (CZTS) thin films. To study the influence of sulfurization temperatures on the CZTS thin films, the CZTS precursor thin films were annealed at temperatures of 520, 540, 560, and 580 °C for 1 h in an H₂S (5 %)+Ar (95 %) atmosphere. These films were characterized for their structural, morphological, and optical properties using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and UV-vis spectrophotometer techniques. The film sulfurized at an optimized temperature of 580 °C shows the formation of a prominent CZTS phase with a dense microstructure and optical band gap energy of 1.38 eV. The photoelectrochemical (PEC) device fabricated using optimized CZTS thin films sulfurized at 580 °C exhibits an open circuit voltage (V_oc) of 0.38 V and a short circuit current density (J_sc) of 6.49 mA cm⁻², with a power conversion efficiency (η) of 0.96 %.     

苯并噻唑衍生物用作EL器件中发光材料的研究

在多层结构的有机电致发光器件（ＥＬ）研制中，一个最富吸引力的提高器件发光效率的方法是通过选择具有高荧光量子产率的发光染料为掺杂剂，加入到作为主体的电子或空穴传输层内，经电子与空穴在主体化合物层内的复合形成激子，经能量转移，激发染料分子，发射染料荧光．...     

Synthesis of a terpolymer containing fluorene,side chain conjugated thiophene and benzothiadiazole and its applications in photovoltaic devices

A terpolymer (POTVTh‐8FO‐DBT) containing fluorene, side chain conjugated thiophene and 4,7‐dithieny‐2,1,3‐benzothiadiazole was synthesized by palladium‐catalyzed Suzuki coupling method. The polymer is soluble in common organic solvents. The thermal, absorption, and electrochemical properties of the polymer were examined. Photovoltaic properties of POTVTh‐8FO‐DBT were studied by fabricating the polymer solar cells (PSCs) based on POTVTh‐8FO‐DBT as donor and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC₆₁BM) as acceptor. With the weight ratio of POTVTh‐8FO‐DBT : PC₆₁BM of 1 : 1 and the active layer thickness of 80 nm, the power conversion efficiency (PCE) of the device reached 0.47% with V_oc = 0.61 V, J_sc = 1.61 mA/cm², and filled factor (FF) = 0.49 under the illumination of AM 1.5, 100 mW/cm². The results indicated that this polymer was promising donor candidates in the application of PSCs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Smooth and highly-crystalline Ag-doped CIGS films sputtered from quaternary ceramic targets

Sputtering with copper indium gallium selenide (CIGS) ceramic targets could produce smooth CIGS thin films that are preferred for preparing two-terminal tandem devices. However, grain sizes prepared in this way are small and device efficiency was low. To increase the grain size, in this report, an Ag layer was pre-sputtered beneath CIGS. The Ag doping layer increased the grain size and improved the crystalline alignment. Consequently, the Ag-doped films exhibited improved charge mobility. From X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy characterizations, we obtained an optimized Ag thickness of 15 nm. Short-circuit current density (J_SC), open-circuit voltage (V_OC), and fill factor (FF) were all improved after doping with 15-nm Ag. Increasing the annealing temperature from 550 °C to 575 °C, the grains was enlarged further, with the power conversion efficiency (PCE) increasing to 14.33% and V_OC to 545 mV. Upon the smooth CIGS film, a thin conformal perovskite layer was fabricated without polishing. This work demonstrates a simple way to fabricate smooth and highly-crystalline CIGS films that can be used for tandem solar cells.     

Logotype-selective electrochromic glass display

This paper describes a fabrication method of a logotype-selective electrochromic (EC) glass. The EC glass performance based on the sample size, WO₃ film thickness, and internal impedances under various applied voltages are also discussed. The logotype-selective electrochromic glass was fabricated by the sputter deposition process. Both working and counter electrode were coated with ITO/WO₃ films. The specific logotypes of “NCUT” and “NUU” can be displayed with positive and negative voltages applied to the EC glass. EC glasses of various sizes (1 cm², 4 cm², 9 cm², 25 cm², and 100 cm²) were also fabricated by sputter deposition process. When voltage (?3.5 V) was applied to the device, the active layer of the assembled device changed from almost transparent to a translucent blue color (colored). The average transmittance in the visible region of the spectrum for a 100 cm² EC device was 73% in the bleached state. The best device, with a 140 nm WO₃ active layer, had average transmittances in the colored and bleached states of 11.9% and 54.8%, respectively. Cyclic voltammogram tests showed that reproducibility of the colored/bleached cycles was good. Nyquist plots showed that increasing the device size decreased the current density, and the electrolyte impedance increased because of a low conductive electrolyte in the device.     

Inverted pyramid Er3+ and Yb3+ Co-doped TiO2 nanorod arrays based perovskite solar cell: Infrared response and improved current density

In this study, a Yb³⁺, Er³⁺ co-doped TiO₂ inverted pyramid nanorod (NR) array and a compact TiO₂ film are simultaneously fabricated as the mesoporous support layer and electron-blocking layer, respectively, by a one-pot hydrothermal method. The scanning electron microscopy results show that the incorporation of Er³⁺ and Yb³⁺ causes changes not only in the growth rate of the NRs, but also in the TiO₂ NR morphology. The Er³⁺, Yb³⁺ co-doped TiO₂ NRs exhibit an inverted pyramidal morphology, which is beneficial for perovskite permeation and light utilization. Notably, the Er³⁺, Yb³⁺ co-doping causes changes in the band gap of TiO₂ and leads to 25% increase in the current density. The electrochemical impedance spectroscopy results show that the device based on the doped TiO₂ NRs has a higher recombination resistance and a lower transfer resistance than those of the undoped device, and thereby, the doped device exhibits a lower electron recombination rate. In addition, the upconversion Er and Yb co-doped device exhibits 25% higher current density and 17% higher photon-to-electron conversion efficiency, as revealed by the J-V test results. Moreover, the optimized efficiency of the TiO₂ NR array-based perovskite solar cell is determined to be 10.02%. Furthermore, the Er and Yb co-doped device exhibits a near-infrared response, an efficiency of 0.1% is achieved under infrared light (800–1100 nm) irradiation. This upconversion material can widen the photovoltaic responses of solar cells into the near-infrared region and improve the utilization of sunlight.