Layer For Perovskite Solar Cells Research Articles

Photoactive Properties of Transport Sol-Gel Layers Based on Strontium Titanate for Perovskite Solar Cells

In this work, we have investigated the photocurrent and spectral sensitivity of the silicon/SrTiO3:xNb/perovskite structures. The sol–gel method carried out the deposition of undoped SrTiO3 layers as well as niobium-doped (SrTiO3:Nb) layers at atomic concentrations of 3 and 6% Nb. The perovskite layer, CH3NH3PbI3−xClx, has been deposited by the vacuum co-evaporation technique. The layers have been characterized by scanning electron microscopy and X-ray diffraction measurements. The volt–ampere characteristics and spectral sensitivity of the fabricated samples have been measured under illumination with selective wavelengths of 405, 450, 520, 660, 780, 808, 905, 980, and 1064 nm of laser diodes. We have shown that for different configurations of applied voltage between silicon, SrTiO3:xNb, and CH3NH3PbI3−xClx, the structures are photosensitive ones with a variation of photocurrent from microamperes to milliamperes depending on Nb concentration in SrTiO3, and the highest photocurrent and spectral sensitivity values are observed when a SrTiO3:Nb layer with 3 at.% of Nb is used. A possible application of the proposed structure with a SrTiO3:Nb layer for perovskite solar cells and photodetectors is being discussed.

Fluorinated carbon nanotubes: a low-cost hole transport layer for perovskite solar cells

Fluorinated carbon nanotubes: a low-cost hole transport layer for perovskite solar cells

Deciphering the role of (Er3+/Nd3+) co-doping effect on TiO2 as an improved electron transport layer in perovskite solar cells

Charge injection and transport at the interface of the electron transport layer (ETL) and perovskite interface are crucial for the perovskite solar cell (PSC) device performance. Titanium dioxide (TiO2) is well established as a photoanode in numerous solar energy conversion and storage. The bandgap engineering of TiO2 by Rare-Earth (RE)-doping has become a significant way to improve the optoelectronic device performance. This study demonstrates the improved performance of Rare-Earth doped TiO2 (RETO) photoanode based solar cells under the doping of Er3+, Nd3+ and following codoping of the (Er3+/Nd3+) effect. It is note that the Er, and Nd dopants are responsible for producing Ti3+ states and the oxygen vacancies near the surface, which drives the charge transportation much more effectively. With the (Er/Nd) codoping into TiO2, the band structure of TiO2 is modified better to make a quasi-Ohmic contact with the perovskites, by fermi level shifting as well changes in the conduction band minima (ECBM) energy states. This results evidence the preliminary conformation for the improvement of Jsc and Voc. Furthermore, the photoluminescence (PL) emission quenching effects of perovskite-deposited RETO attributes the suppression in the charge recombination. By insight into all these favourable results in the(Er3+/Nd3+) codoped TiO2, the RETO photoanode-based perovskite solar cell (PSC) devices were constructed and exhibited improved photovoltaic properties. The composition of (Er0.002Nd0.002Ti0.996O2) ETL employed PSC reported with a better photoconversion efficiency (PCE %) among all the compositions.

Molecule‐Assisted Chemical Bath Deposition of Tin Oxide Electron Transport Layers in Perovskite Solar Cells

Chemical bath deposition (CBD) is a widely used approach to deposit the tin oxide (SnO2) electron transport layer (ETL) in the perovskite solar cell (PSC). However, the defect states in the CBD‐resulted SnO2 ETLs limit the electron extraction/transport from the perovskite to the ETL and lead to poor PSC performance. Herein, ethylenediaminetetraacetic acid dipotassium (EDTA‐2K) is used as an additive in the CBD precursor of the SnO2 ETL, which results in the chelation of Sn2+ and EDTA during the hydrolysis process. This strategy decreases the concentration of free Sn2+ in the precursor for hydrolysis and slows down the CBD process, thus attributes to the decreased surface defect states as well as the enhanced conductivity of the ETL. As a result, the EDTA‐2K additive makes the CBD SnO2 ETL with efficient electron extraction and transporting capability. The champion device achieves a power conversion efficiency (PCE) of 21.87%, which is significantly higher than that of the pristine CBD SnO2‐based device (20.25%). In addition, the device with an active area of 1.21 cm2 achieves a high PCE of 19.23%. This strategy makes the CBD SnO2 an excellent ETL candidate for the development of low‐cost and large‐scale PSCs.

Metal oxide nanoparticles as an electron-transport layer in perovskite solar cell

The research on the application of lead-free perovskite materials as an active layer in solar cells has been positively carried out for the last few years. Although the efficiency of lead-contained metal halide-based Perovskite has reached above 25%, but lead is a highly toxic substance that is hazardous to the environment, and this is one of the obstacles to their commercialization. In this article, a Sn-based Perovskite (CH3NH3SnI3) solar cell with two distinct electron transport layers was simulated using GPVDM (General Purpose Photovoltaic Device Model) and fabricated with a simple sol-gel method. Along with the absorber layer, the charge transport materials also play an essential role in extracting electrical power. The comparison of ZnO and TiO2 as electron collectors has been investigated and characterized, the hole-carrying layer has been eliminated for better findings. Remarkably, we achieve an efficiency of 7.33% and 6.75% in simulation and 6.90% and 5.81% from fabricated devices using ZnO and TiO2, respectively.

Nitrogen-Doped Graphene Quantum Dot–Tin Dioxide Nanocomposite Ultrathin Films as Efficient Electron Transport Layers for Planar Perovskite Solar Cells

Tin dioxide (SnO2) has recently been recognized as an excellent electron transport layer (ETL) for perovskite solar cells (PSCs) due to its advantageous properties, such as its high electron mobility, suitable energy band alignment, simple low-temperature process, and good chemical stability. In this work, nitrogen-doped graphene quantum dots (N-GQDs) were prepared using a hydrothermal method and then used to fabricate N-GQD:SnO2 nanocomposite ultrathin films. N-GQD:SnO2 nanocomposite ultrathin films were investigated and applied as electron transport layers in planar PSCs. The presence of N-GQDs with an average size of 6.2 nm in the nanocomposite improved its morphology and reduced surface defects. The excitation–emission contour map indicated that the N-GQDs exhibited a remarkably enhanced light-harvesting capability due to the possibility of absorbing UV light and producing emissions in the visible range. The quenching of photoluminescence spectra showed that the N-GQDs in nanocomposite ultrathin films improved electron extraction and reduced charge recombination. As a result, the power conversion efficiency (PCE) of our planar PSCs fabricated with the optimized N-GQD:SnO2 nanocomposite electron transport layer was improved by 20.4% over pristine SnO2-based devices.

Synergistic Defect Passivation by Metformin Halides for Improving Perovskite Solar Cell Performance

Defect passivation plays a critical role in manufacturing high-performance perovskite solar cells (PSCs). Herein, engineered components of metformin halides are introduced to the bulk and surface of perovskite layers in PSCs to realize synergistic defect passivation. It is found that the bulk addition of metformin hydrochloride influences the orientation distribution of perovskite crystals and contributes to better perovskite films. Further, the modification of metformin iodide could treat residual defects on the surface of perovskite films. As a result, the synergistically passivated PSCs shows an improved power conversion efficiency (PCE), which increased from 19.36% to 22.17%, together with a higher short-circuit current and open-circuit voltage than those of the control device. Moreover, the as-treated PSCs exhibit excellent thermal and humidity stabilities, maintaining 95% of their initial PCE after being stored under air conditions for over 1000 h. This work provides a novel strategy to passivate perovskite defects and improve the PCE and stability of PSCs.

The Effect of Different Precursor Solutions on the Structural, Morphological, and Optical Properties of Nickel Oxide as an Efficient Hole Transport Layer for Perovskite Solar Cells

Perovskite solar cell (PSC) technologies have recently become a popular research topic. The hole transport layers (HTL) are important in establishing stable and efficient PSC by regulating charge absorption, interlayer recombination losses, and band alignment. Spiro-OMeTAD was extensively used as the HTL to fabricate highly efficient PSCs. Despite Spiro-OMeTAD having the benefit of providing high PCEs, it is costly, hazardous to the ecology, and cannot provide high efficiencies in the lack of additional additives that can reduce their stabilities. Inorganic HTL, specifically nickel oxide (NiO), has garnered much interest due to its low-cost, enhanced mobility, and strong stability to attain high efficiency. This study investigated different precursor solutions of NiO synthesis (Method I, II, and III) and deposited using the spin coating approach. The films were annealed at different annealing temperatures (400°C, 550°C, and 700°C) and evaluated by X-ray powder diffraction (XRD), UV-Vis spectroscopy, and Scanning electron microscopy (SEM) to test their structural, morphological, and optical characteristics, respectively. The findings of XRD revealed that a higher annealing temperature increases the crystallite size and decreases the microstrain through the study from Scherrer’s and Williamson-Hall’s (WH) equations. From the SEM analysis, the films show uniformity, large crystals, and agglomeration of particles. The annealing temperature from 400°C to 700°C reduced bandgap energy from 3.6 eV to 2.1 eV. According to the result, NiO produced at an annealing temperature of 700°C (Method I) exhibited the best characteristics and might be a viable option for HTL in PSCs.

Effects of Carrier Transport Layers on Performance Degradation in Perovskite Solar Cells under Proton Irradiation

Perovskite solar cells (PSCs) are potentially ideal for use in space satellites and spacecraft. While perovskites were found to be robust to space particle irradiations, it is important to investigate the influences of the carrier transport layers in PSCs on the irradiation-induced performance degradation. This study reports on the responses of different CsMAFAPbI3-based PSCs to 250 keV proton irradiation. Spiro-OMeTAD is used as a hole transport material in the cells, whereas SnO2, TiO2, and In2O3 are used as electron transport materials. After irradiation, the three different cells are not degraded up to 1 × 1013 p/cm2 and follow a similar degradation trend with further increasing the proton fluence until they are completely destroyed at 6 × 1014 p/cm2. By means of recycling, it is shown that SnO2, TiO2, and In2O3 have little influence on cell degradation, although the square resistances of SnO2, TiO2, and In2O3 on FTO/glass substrates are increased by 15–19% after irradiation of 6 × 1014 p/cm2; instead, the degradation of the spiro-OMeTAD material accounts for the reduced performance of the PSCs. The proton irradiation leads to a de-doping effect of spiro-OMeTAD, causing an efficiency decrease of the PSCs. A more radiation-resistant hole transport material to replace spiro-OMeTAD is therefore warranted to extend the lifetime of the PSCs in space environments.

Enhanced Performance of CsPbIBr2 Perovskite Solar Cell by Modified Zinc Oxide Nanorods Array with [6,6]-Phenyl C61 Butyric Acid.

Although Metal oxide ZnO is widely used as electron transport layers in all-inorganic PSCs due to high electron mobility, high transmittance, and simple preparation processing, the surface defects of ZnO suppress the quality of perovskite film and inhibit the solar cells' performance. In this work, [6,6]-Phenyl C61 butyric acid (PCBA) modified zinc oxide nanorods (ZnO NRs) is employed as electron transport layer in perovskite solar cells. The resulting perovskite film coated on the zinc oxide nanorods has better crystallinity and uniformity, facilitating charge carrier transportation, reducing recombination losses, and ultimately improving the cells' performance. The perovskite solar cell with the device configuration of ITO/ZnO nanorods/PCBA/CsPbIBr2 /Spiro-OMeTAD/Au delivers a high short circuit current density of 11.83 mA cm-2 and power conversion efficiency of 12.05 %.

Boosting efficiency of eco-friendly perovskite solar cell through optimization of novel charge transport layers.

Formamidinium tin triiodide (FASnI3) is a suitable candidate for the absorber layer in perovskite solar cells (PSC) because of its non-toxicity, narrow band gap, thermal stability and high carrier mobility. This study focuses on the analysis and improvement in the performance of FASnI3-based PSCs using various inorganic charge transport materials. The copper-based materials such as Cu2O, CuAlO2, CuSCN and CuSbS2 are introduced as hole transport layers due to their earth abundance, ease of manufacturing, high charge mobilities and chemical stability. Similarly, fullerene derivates (PCBM and C60) are deployed as electron transport layers due to their mechanical strength, thermal conductivity and stability. The effect of these materials on optical absorption, quantum efficiency, energy band alignment, band offsets, electric field and recombination are studied in detail. The reasons for the low performance of the cell are identified and improved through design optimization. The PSC performance is analysed in both inverted and conventional architecture. Among all the structures, the best result is achieved through ITO/CuSCN/FASnI3/C60/Al with an efficiency of 27.26%, Voc of 1.08 V, Jsc of 29.5 mAcm-2 and FF of 85.6%.

P3CPenT as an organic hole transport layer for perovskite solar cells

AbstractPerovskite solar cells (PSC) are the third‐generation solar cells, which have a low production cost and have achieved similar laboratory scale efficiencies as the first‐generation silicon solar cells. In the present work, we performed density functional theory calculations on the organic material, poly[3‐(5‐carboxypentyl) thiophene‐2,5‐diyl] regioregular (P3CPenT). The ground state and excited state properties of P3CPenT are calculated. The HOMO‐LUMO levels and electronic bandgap obtained from the calculations are compared with the experimental values for validation of the theory. A high electron reorganization energy and low hole reorganization energy ensures that P3CPenT aids the flow of holes and hinders the flow of electrons. The optical bandgap and low exciton binding energy indicates its potential as a hole transport layer (HTL). The ease of fabrication of P3CPenT is established by showing that the oligomer is soluble in dimethyl sulfoxide (DMSO), which is the most commonly utilized solvent for the fabrication of PSCs. The hydrophobic nature of P3CPenT as established by the present work shows that it is stable with moisture and would thus protect the underlying MAPbI3 perovskite layer from decomposing and hence improve its lifetime and stability. Fill factor (FF) of 78.07% and a power conversion efficiency (PCE) of 14.88% has been obtained for PSC with P3CPenT HTL.

High-Performance Perovskite Solar Cells and Modules Fabricated by Slot-Die Coating with Nontoxic Solvents.

Energy shortage has become a global issue in the twenty-firt century, as energy consumption grows at an alarming rate as the fossil fuel supply exhausts. Perovskite solar cells (PSCs) are a promising photovoltaic technology that has grown quickly in recent years. Its power conversion efficiency (PCE) is comparable to that of traditional silicon-based solar cells, and scale-up costs can be substantially reduced due to its utilization of solution-processable fabrication. Nevertheless, most PSCs research uses hazardous solvents, such as dimethylformamide (DMF) and chlorobenzene (CB), which are not suitable for large-scale ambient operations and industrial production. In this study, we have successfully deposited all of the layers of PSCs, except the top metal electrode, under ambient conditions using a slot-die coating process and nontoxic solvents. The fully slot-die coated PSCs exhibited PCEs of 13.86% and 13.54% in a single device (0.09 cm2) and mini-module (0.75 cm2), respectively.

Charge carrier dynamics across the metal oxide/BaTiO3 interfaces toward photovoltaic applications from the theoretical perspective

Transport layers in perovskite solar cells are the crucial parts in charge carrier extraction and transfer in the solar cell circuit. The physical and chemical properties of their interfaces with neighbouring layers, such as buffer layers, govern the dynamics of electrons across the interface boundaries. Using ab initio calculations, we study in detail the interface properties of metal oxide/BaTiO3 heterostructures. The structural changes near the metal oxide/BaTiO3 interfaces are detailed for the first time. The electronic properties are used to assess the quantities of interest for use in perovskite solar cells (band gap, effective mass, carrier mobility, plane averaged electrostatic potential, band offsets). The analysed results introduce several competing quantities which influence the charge dynamics: the band gap character versus the charge carrier effective mass and the averaged electrostatic potential difference versus the unfavourable conduction band offset. While experimental studies are unable to distinguish the relevance of the competing factors, our results point to the fact that BaTiO3 interlayer morphology plays a more important factor in the cell's performance than its intrinsic properties. Based on the results, general insights are given on the structural requirements for improved buffer layer materials in combinations with metal oxide transport layer used as substrates in the solar cell architecture.

PbS-TBAI / MoSe2-grating as new hole transport layer in perovskite solar cells: Superior efficiency enhancement thru simulation and optimization

For the first time, we increased the power conversion efficiency (PCE) of a perovskite solar cell (PSC) from 13.82% to 19.45%, by presenting a new structure of hole transport layer (HTL) consisting of spherical PbS-QD layer treated with tetrabutylammonium iodide (PbS-TBAI) and MoSe2 in the form of grating. MoSe2 with smaller bandgap than perovskite (CH3NH3PbI3) when used instead of CuSCN in the hole transport layer (HTL), can help absorb higher wavelengths and generate electron-hole pairs, which increases Jsc (short-circuit current density), Voc (open-circuit voltage) and PCE respectively from 17.2 to 20.8 mA/cm2, 0.97–1.21 V and 13.82–17.67%. However, due to the reduction of fill factor (FF), the arrangement of different layers to block electrons was investigated, which we found that employing grating structure can improve FF by 4%, while the other parameters do not change much (PCE: 17.67→17.3). Then, a spherical PbS-QD layer treated with tetrabutylammonium iodide (PbS-TBAI) was implemented inside the MoSe2 layer in grating form structure with Spiro to enhance the absorption and consequently the PCE. As a result, this change caused the increase of Jsc, FF and PCE, from 20.82 to 24.15 mA/cm2, 0.73–0.79 and 17.3–19.45%, respectively.

Effect of phthalocyanine-based charge transport layers on unleaded KSnI3 perovskite solar cell

The implementation and commercialization of perovskite solar cells (PSCs) are hindered due to the presence of toxic lead. Metal phthalocyanines (MPc) have been studied extensively as charge transport layers (CTLs) in PSCs due to their desirable properties such as thermal and chemical robustness, and low production cost. In the present work, a theoretical study of the effect of phthalocyanine-based CTLs on a non-leaded KSnI3-based PSC is carried out using SCAPS software. The defect concentration of the layers and the interfaces, doping density and thickness of the layers, shunt, and series resistance of the device is optimized. Carbon is suggested as an affordable alternative to the state of art back contact material, gold. The stability of this device with temperature is also established. The optimized solar cell showed an excellent fill factor (FF) of 86.51% with a power conversion efficiency (PCE) of 11.91% and an excellent quantum efficiency (QE) ranging from 99.42%(400 nm) to 72.02%(660 nm) in the visible region. The present study highlights the enhanced performance parameters of leadless KSnI3-based PSC with phthalocyanine-based CTLs as compared to the state-of-art CTLs, TiO2 and Spiro-OMeTAD reported in previous literature with a PCE and FF of 9.776% and 36.139% respectively.

Efficiency improvement of CTL-free PSCs based on Sn-/Pb-perovskite heterojunction: a numerical approach

Perovskite solar cells (PSCs) with no charge transport layer (CTL) have drawn great attentions due to their simple device structure and low cost. However, the low efficiency hampers their practical applications. In the study, a novel FASnI3/MAPbI3 heterojunction structure is proposed to replace the conventional MAPbI3 absorber layer for efficient CTL-free PSCs. The numerical tool SCAPS-1D is employed to optimize the proposed structure taking into account multiple device and material parameters, such as layer thickness, doping concentration of MAPbI3, electron affinity of FASnI3 and back electrode work function. After optimization, the highest yielded efficiency of the FASnI3/MAPbI3 bilayer structure is 25.34%, which is 54.9% relatively higher than the conventional MAPbI3 single-layer structure (with an optimal efficiency of 16.36%). The simulation results demonstrate the huge potentials of proposed FASnI3/MAPbI3 heterojunction for constructing efficient CTL-free PSCs and provide inspirations for the future development of CTL-free PSCs.

N,N-Bis(9-methyl-3-carbazolyl)-4-anisidine as an Electroactive Material for Use in Perovskite Solar Cells.

Di(9-methyl-3-carbazolyl)-(4-anisyl)amine is presented as an effective hole-transporting material suitable for application in perovskite solar cells. It is obtained by a three-step synthesis from inexpensive starting compounds. It has a relatively high glass transition temperature of 93 °C and thermal stability with 5% weight loss at 374 °C. The compound exhibits reversible double-wave electrochemical oxidation below +1.5 V and polymerization at higher potential. A mechanism for its oxidation is proposed based on electrochemical impedance and electron spin resonance spectroscopy investigations, ultraviolet-visible-near-infrared absorption spectroelectrochemistry results, and density functional theory-based calculations. Vacuum-deposited films of the compound are characterized by a low ionization potential of 5.02 ± 0.06 eV and hole mobility of 10-3 cm2/(Vs) at an electric field of 4 × 105 V/cm. The newly synthesized compound has been used to fabricate dopant-free hole-transporting layers in perovskite solar cells. A power conversion efficiency of 15.5% was achieved in a preliminary study.

Multi-functional MXene quantum dots enhance the quality of perovskite polycrystalline films and charge transport for solar cells

Recently, two-dimensional (2D) transition metal carbides/nitrides (MXenes) find applications in perovskite solar cells (PSCs), due to their high conductivity, tunable electronic structures, and rich surface chemistry, etc. However, the integration of 2D MXenes into PSCs is limited by their large lateral sizes and relatively-small surface volume ratios, and the roles of MXenes in PSCs are still ambiguous. In this paper, zero-dimensional (0D) MXene quantum dots (MQDs) with an average size of 2.7 nm are obtained through clipping step by step combining a chemical etching and a hydrothermal reaction, which display rich terminals (i.e., -F, –OH, -O) and unique optical properties. The 0D MQDs incorporated into SnO2 electron transport layers (ETLs) of PSCs exhibit multifunction: 1) increasing the electrical conductivity of SnO2, 2) promoting better alignments of energy band positions at the perovskite/ETL interface, 3) improving the film quality of atop polycrystalline perovskite. Particularly, the MQDs not only tightly bond with the Sn atom for decreasing the defects of SnO2, but also interact with the Pb2+ of perovskite. As a result, the defect density of PSCs is significantly decreased from 5.21 × 1021 to 6.4 × 1020 cm-3, leading to enhanced charge transport and reduced nonradiative recombination. Furthermore, the power conversion efficiency (PCE) of PSCs is substantially improved from 17.44% to 21.63% using the MQDs-SnO2 hybrid ETL compared with the SnO2 ETL. Besides, the stability of the MQDs-SnO2-based PSC is greatly enhanced, with only ～4% degradation of the initial PCE after storage in ambient condition (25 °C, RH: 30-40%) for 1128 h, as compared to that of the reference device with a rapid degradation of ～60% of initial PCE after 460 h. And MQDs-SnO2-based PSC also presents higher thermal stability than SnO2-based device with continuous heating for 248 h at 85 °C. The unique MQDs exhibited in this work might also find other exciting applications such as light-emitting diodes, photodetectors, and fluorescent probes.

Multifunctional Cross‐Linked Polyurethane Polymer as Interface Layer for Efficient and Stable Perovskite Solar Cells

AbstractIn the past decade, perovskite solar cells (PSCs) have made remarkable progress in improving power conversion efficiency (PCE). In order to further improve the photovoltaic performance and long‐term stability of PSCs, the interface layer is essential. A multifunctional cross‐linked polyurethane (CLPU) is designed and synthesized via the spontaneous quaternization of polyurethane and 1, 6‐diiodohexane on the surface of the perovskite layer. CLPU layer cannot only effectively induce secondary crystallization and passivate the surface defects of perovskite, reduce the non‐radiative recombination, but also effectively block the moisture invasion. By this strategy, Cs0.05FA0.95PbI3 PSCs with excellent reproducibility, is realized, achieving a PCE of 23.14% with an open‐circuit voltage of 1.11 V, a short‐circuit current density of 25.69 mA cm−2, and a fill factor of 0.81. In addition, the unencapsulated devices show enhanced stability in 35 ± 5% relative humidity (RH) near 3000 h and in 65 ± 5% RH over 700 h. This study provides valuable insights into the role of CLPU interface layer in PSCs, which are essential for the design of high‐performance devices.