A Short Progress Report on High-Efficiency Perovskite Solar Cells

Stability Strategies and Applications of Iodide Perovskites

Iodide perovskites have demonstrated their unprecedented high efficiency and commercialization potential, and their superior optoelectronic properties, such as high absorption coefficient, high carrier mobility, and narrow direct bandgap, have attracted much attention, especially in solar cells, photodetectors, and light-emitting diodes (LEDs). However, whether it is organic iodide perovskite, organic-inorganic hybrid iodide perovskite or all-inorganic iodide perovskite the stability of these iodide perovskites is still poor and the contamination is high. In recent years, scholars have studied more iodide perovskites to improve their stability as well as optoelectronic properties from various angles. This paper systematically reviews the strategies (component engineering, additive engineering, dimensionality reduction engineering, and phase mixing engineering) used to improve the stability of iodide perovskites and their applications in recent years.

Topography and Nonlinear Optical Properties of Thin Films Containing Iodide-Based Hybrid Perovskites

This article covers selected properties of organic-inorganic thin films of hybrid perovskites with the summary formulas CH3NH3MI3, where M = Pb, Cd, Ge, Sn, Zn. The paper discusses not only the history, general structure, applications of perovskites and the basics of the theory of nonlinear optics, but also the results of experimental research on their structural, spectroscopic, and nonlinear optical properties. The samples used in all presented studies were prepared in the physical vapor deposition process by using co-deposition from two independent thermal sources containing the organic and inorganic parts of individual perovskites. Ultimately, thin layers with a thickness of the order of nanometers were obtained on glass and crystalline substrates. Their structural properties were characterized by atomic force microscopy imaging. Spectroscopic tests were used to confirm the tested films' transmission quality and determine previously unknown physical parameters, such as the absorption coefficient and refractive index. Experimental results of the nonlinear optical properties were obtained by studying the second and third harmonic generation processes and using initial sample polarization in the so-called Corona poling process. The obtained experimental results allowed us to determine the second- and third-order nonlinear optical susceptibility of the tested materials.

A2LiGaI6 (A = Cs, Rb): New lead-free and direct bandgap halide double perovskites for IR application

Recently, all inorganic double perovskites have drawn a lot of interest as promising solar materials. The optical, structural, thermoelectric, electronic, and mechanical properties of double halide perovskites A2LiGaI6 (A = Cs, Rb) are explored via first-principles calculations with the WIEN2k code, using GGA PBEsol and TB-mBJ potentials. The majority of perovskite materials utilized in the highest-performing solar cells have bandgaps ranging between 1.48 and 1.62 eV. The compounds A2LiGaI6 (A = Cs, Rb) have a direct bandgap of 1.51 eV and 1.55 eV, respectively, and are expected to be useful in solar cells. The optical study shows that there are large absorption bands in the visible region, as determined by the dielectric constant, absorption, and other dependent factors. Their potential for use in solar cells is increased by their absorption in the visible part. The BoltzTraP code has been used to perform thermoelectric studies to assess the electrical, thermal conductivities, and Seebeck coefficient. They are important for construction of thermoelectric generators that harvest heat energy because of their high figure of merit and incredibly low thermal conductivity of lattice at ambient temperature. Furthermore, by examining the spectroscopic limit maximum efficiency, up to 30 % efficiency is predicted for both compositions, which paves the way for the applicability of them in solar energy conversion.

Combined DFT, SCAPS-1D, and wxAMPS frameworks for design optimization of efficient Cs2BiAgI6-based perovskite solar cells with different charge transport layers

In this study, combined DFT, SCAPS-1D, and wxAMPS frameworks are used to investigate the optimized designs of Cs2BiAgI6 double perovskite-based solar cells. First-principles calculations are employed to investigate the structural stability, optical responses, and electronic contribution of the constituent elements in Cs2BiAgI6 absorber material, where SCAPS-1D and wxAMPS simulators are used to scrutinize different configurations of Cs2BiAgI6 solar cells. Here, PCBM, ZnO, TiO2, C60, IGZO, SnO2, WS2, and CeO2 are used as ETL, and Cu2O, CuSCN, CuSbS2, NiO, P3HT, PEDOT:PSS, spiro-MeOTAD, CuI, CuO, V2O5, CBTS, CFTS are used as HTL, and Au is used as a back contact. About ninety-six combinations of Cs2BiAgI6-based solar cell structures are investigated, in which eight sets of solar cell structures are identified as the most efficient structures. Besides, holistic investigation on the effect of different factors such as the thickness of different layers, series and shunt resistances, temperature, capacitance, Mott-Schottky and generation-recombination rates, and J-V (current-voltage density) and QE (quantum efficiency) characteristics is performed. The results show CBTS as the best HTL for Cs2BiAgI6 with all eight ETLs used in this work, resulting in a power conversion efficiency (PCE) of 19.99%, 21.55%, 21.59%, 17.47%, 20.42%, 21.52%, 14.44%, 21.43% with PCBM, TiO2, ZnO, C60, IGZO, SnO2, CeO2, WS2, respectively. The proposed strategy may pave the way for further design optimization of lead-free double perovskite solar cells.

High-Performance Quasi-Two-Dimensional CsPbBr2.1Cl0.9:PEABr Perovskite Sky-Blue LEDs with an Interface Modification Layer

This paper elucidates the increased luminescence efficiency of CsPbBr2.1Cl0.9 sky-blue perovskite light-emitting diodes (PeLEDs) achieved through the interface modification of 3,4 ethylenedioxythiophene (PEDOT):polystyrene sulfonic acid (PSS)/quasi-two-dimensional (QTD) perovskite using CsCl and CsBr materials, respectively. QTD films were fabricated using ratios of CsPbBr2.1Cl0.9 doped with phenethylamine hydrobromide (PEABr) at 60%, 80%, and 100%. The solvent dimethyl sulfide (C2H6OS) was employed under the excitation of ambient and 365-nm laser lights. The PeLED structure was composed of Al/LiF/2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi)/CsPbBr2.1Cl0.9:PEABr/interface modification layer/PEDOT:PSS/ITO glass. The optimized results revealed that the luminance, current efficiency, and external quantum efficiency of the QTD CsPbBr2.1Cl0.9:80% PEABr PeLED with the CsCl interface modification additive was 892 cd/m2, 3.87 cd/A, and 5.56%, respectively.

Synthesis and Characterization of High-Efficiency Halide Perovskite Nanomaterials for Light-Absorbing Applications

Inorganic perovskite materials are possible candidates for conversion of solar energy to electrical energy due to their high absorption coefficient. Perovskite solar cells (PSCs) introduced a new type of device structure that has attention due to better efficiencies and interest in PSCs that has been increasing in recent years. Halide perovskite materials such as CsPbIBr₂ show remarkable optical and structural performance with their better physical properties. Perovskite solar cells are a possible candidate to replace conventional silicon solar panels. In the present study, CsPbIBr₂ perovskite materials' thin films were prepared for light-absorbing application. Five thin films were deposited on the glass substrates by subsequent spin-coating of CsI and PbBr₂ solutions, subsequently annealed at different temperature values (as-deposited, 100, 150, 200 and 250 °C) to get CsPbIBr₂ thin films with a better crystal structure. Structural characterizations were made by using X-ray diffraction. CsPbIBr₂ thin films were found to be polycrystalline in nature. With increasing annealing temperature, the crystallinity was improved, and the crystalline size was increased. Optical properties were studied by using transmission data, and by increasing annealing temperature, a small variation in optical band gap energy was observed in the range of 1.70-1.83 eV. The conductivity of CsPbIBr₂ thin films was determined by a hot probe technique and was found to have little fluctuating response toward p-type conductivity, which may be due to intrinsic defects or presence of CsI phase, but a stable intrinsic nature was observed. The obtained physical properties of CsPbIBr₂ thin films suggest them as a suitable candidate as a light-harvesting layer. These thin films could be an especially good partner with Si or other lower band gap energy materials in tandem solar cells (TSC). CsPbIBr₂ material will harvest light having energy of ∼1.7 eV or higher, while a lower energy part of the solar spectrum will be absorbed in the partner part of the TSC.

A Review of Recent Developments in Preparation Methods for Large-Area Perovskite Solar Cells

The recent rapid development in perovskite solar cells (PSCs) has led to significant research interest due to their notable photovoltaic performance, currently exceeding 25% power conversion efficiency for small-area PSCs. The materials used to fabricate PSCs dominate the current photovoltaic market, especially with the rapid increase in efficiency and performance. The present work reviews recent developments in PSCs’ preparation and fabrication methods, the associated advantages and disadvantages, and methods for improving the efficiency of large-area perovskite films for commercial application. The work is structured in three parts. First is a brief overview of large-area PSCs, followed by a discussion of the preparation methods and methods to improve PSC efficiency, quality, and stability. Envisioned future perspectives on the synthesis and commercialization of large-area PSCs are discussed last. Most of the growth in commercial PSC applications is likely to be in building integrated photovoltaics and electric vehicle battery charging solutions. This review concludes that blade coating, slot-die coating, and ink-jet printing carry the highest potential for the scalable manufacture of large-area PSCs with moderate-to-high PCEs. More research and development are key to improving PSC stability and, in the long-term, closing the chasm in lifespan between PSCs and conventional photovoltaic cells.

Net Zero Energy Districts: Connected Intelligence for Carbon-Neutral Cities

Net-Zero Energy Districts (NZEDs) are city districts in which the annual amount of CO2 emissions released is balanced by emissions removed from the atmosphere. NZEDs constitute a major component in a new generation of “smart-green cities”, which deploy both smart city technologies and renewable energy technologies. NZEDs promote environmental sustainability, contribute to cleaner environments and reduce global warming and the threats from climate change. This paper describes a model to assess the feasibility of the transition of city districts to self-sufficient NZEDs, based on locally produced renewable energy suitable for cities. It also aims to identify threshold conditions that allow for a city district to become a self-sufficient NZED using smart city systems, renewable energy, and nature-based solutions. The significance of transition to self-sufficient NZEDs is extremely important as it considerably decentralises and multiplies the efforts for carbon-neutral cities. The methodology we follow combines the literature review, model design, model feed with data, and many simulations to assess the outcome of the model in various climate, social, technology, and district settings. In the conclusion, we assess whether the transition to NZEDs with solar panel energy locally produced is feasible, we identify thresholds in terms of climate, population density, and solar conversion efficiency, and assess the compatibility of NZEDs with compact city planning principles.

Strategies towards Cost Reduction in the Manufacture of Printable Perovskite Solar Modules

Among different perovskite solar cell architectures, the carbon-based perovskite solar cell (C-PSC) is a promising candidate for upscaling and commercialization related to low-cost components and simple manufacturing methods. For upscaling a PV technology, three parameters must be considered, corresponding to efficiency, stability, and cost. While the efficiency and lifetime of perovskite technology are the focus of many research groups, the cost parameter is less studied. This work aims to provide information on the manufacturing cost of C-PSC based on experimental data in order to give the readers a panoramic overview of parameters influencing a fabrication process. To analyze the commercialization viability of this technology, we estimated the cost of raw materials and the manufacturing process for sub-modules using two different methods: registration and scribing. The fabrication cost of a sub-module fabricated using the scribing method with 7.9% efficiency was approximately 44% less than that of a device with 6.8% efficiency prepared using registration. We demonstrated that this is due to both the design parameters and performance. In addition, we showed a 51% cost reduction for registration devices by appropriate choice of solar cell components, fabrication steps, and equipment based on the existing infrastructures for the manufacturing of large-scale devices.

Perovskite indoor photovoltaics: opportunity and challenges

With the rapid development of the Internet of Things (IoTs), photovoltaics (PVs) has a vast market supply gap of billion dollars. Moreover, it also puts forward new requirements for the development of indoor photovoltaic devices (IPVs). In recent years, PVs represented by organic photovoltaic cells (OPVs), silicon solar cells, dye-sensitized solar cells (DSSCs), etc. considered for use in IoTs mechanisms have also been extensively investigated. However, there are few reports on the indoor applications of perovskite devices, even though it has the advantages of better performance. In fact, perovskite has the advantages of better bandgap adjustability, lower cost, and easier preparation of large-area on flexible substrates, compared with other types of IPVs. This review starts from the development status of IoTs and investigates the cost, technology, and future trends of IPVs. We believe that perovskite photovoltaics is more suitable for indoor applications and review some strategies for fabricating high-performance perovskite indoor photovoltaic devices (IPVs). Finally, we also put forward a perspective for the long-term development of perovskite IPVs.

A Bayesian fusion technique for maximum power point tracking under partial shading condition

In this paper, a Bayesian fusion technique (BFT) based on maximum power point tracking (MPPT) is developed for the photovoltaic (PV) system that can exhibit faster and accurate tracking under partially shaded conditions (PSCs). Although the conventional hill-climbing algorithms have fast tracking capabilities, they are prone to steady-state oscillations and may not guarantee global peak under partially shaded conditions. Contrarily, the meta-heuristic-based techniques may promise a global peak solution, but they are computationally inefficient and take significant time for tracking. To address this problem, a BFT is proposed which combines the solutions obtained from conventional incremental conductance algorithm and Jaya optimization algorithm to produce better responses under various PSCs. The effectiveness of the proposed BFT-based MPPT is evaluated by comparing it with various MPPT methods, viz. incremental conductance, particle swarm optimization (PSO), and Jaya optimization algorithms in MATLAB/Simulink environment. From the various case studies carried, the overall average tracking speed with more than 99% accuracy is less than 0.25 s and having minimum steady-state oscillations. Even under the wide range of partially shaded conditions, the proposed method exhibited superior MPPT compared to the existing methods with tracking speed less than 0.1 s to achieve 99.8% tracking efficiency. A detailed comparison table is provided by comparing with other popular existing MPPT methodologies.

A Small Hybrid Power System of Photovoltaic Cell and Sodium Borohydride Hydrolysis-Based Fuel Cell

Although the hybrid power system that combines a photovoltaic cell and a lithium-ion battery is increasingly mature and practical, long-lifetime auxiliary power will be still needed in severe weather conditions. A small-volume hydrogen-oxygen fuel cell system based on the hydrolysis of NaBH4 is designed. The fuel cell system contains a tiny hydrogen generator, a hydrogen cleaner, and a small fuel cell stack consisting of three units in series. The relationship between the amount of catalyst and output performance is discussed. The long-time discharging results indicate that the fuel cell system has high power capacity. The compact design allows the fuel cell system to integrate the structure with a photovoltaic cell and lithium-ion cell and forms a hybrid power system with a small package. The power management circuit for these power sources without logic devices is designed and tested. The control strategy selects the photovoltaic-battery subsystem as the primary power source, and the fuel cell subsystem works as the backup power source to handle the circumstance when the energy stored in the battery is exhausted. The test results show that the power management system could switch the power supply automatically and timely under various emergency conditions, and the output voltage remains stable all the time.

Investigations aimed at producing 33% efficient perovskite–silicon tandem solar cells through device simulations

The conversion efficiencies for silicon-based photovoltaic devices have become stagnant, with the record conversion efficiency of 26.7% achieved in 2017.

Perovskite Solar Cells for BIPV Application: A Review

The rapid efficiency enhancement of perovskite solar cells (PSCs) make it a promising photovoltaic (PV) research, which has now drawn attention from industries and government organizations to invest for further development of PSC technology. PSC technology continuously develops into new and improved results. However, stability, toxicity, cost, material production and fabrication become the significant factors, which limits the expansion of PSCs. PSCs integration into a building in the form of building-integrated photovoltaic (BIPV) is one of the most holistic approaches to exploit it as a next-generation PV technology. Integration of high efficiency and semi-transparent PSC in BIPV is still not a well-established area. The purpose of this review is to get an overview of the relative scope of PSCs integration in the BIPV sector. This review demonstrates the benevolence of PSCs by stimulating energy conversion and its perspective and gradual evolution in terms of photovoltaic applications to address the challenge of increasing energy demand and their environmental impacts for BIPV adaptation. Understanding the critical impact regarding the materials and devices established portfolio for PSC integration BIPV are also discussed. In addition to highlighting the apparent advantages of using PSCs in terms of their demand, perspective and the limitations, challenges, new strategies of modification and relative scopes are also addressed in this review.

An Emerging Visible-Light Organic-Inorganic Hybrid Perovskite for Photocatalytic Applications

The development of visible-light active photocatalysts is a current challenge especially energy and environmental-related fields. Herein, methylammonium lead iodide perovskite (MAIPb) was chosen as the novel semiconductor material for its ability of absorbing visible-light. An easily reproducible and efficient method was employed to synthesize the as-mentioned material. The sample was characterized by various techniques and has been used as visible-light photocatalyst for degradation of two model pollutants: rhodamine B (RhB) and methylene-blue (MB). The photo-degradation of RhB was found to achieve about 65% after 180 min of treatment. Moreover, the efficiency was enhanced to 100% by assisting the process with a small amount of H2O2. The visible-light activity of the photocatalyst was attributed to its ability to absorb light as well as to enhance separation of photogenerated carriers. The main outcome of the present work is the investigation of a hybrid perovskite as photocatalyst for wastewater treatment.

Optimizing the Interface between Hole Transporting Material and Nanocomposite for Highly Efficient Perovskite Solar Cells

The performances of organometallic halide perovskite-based solar cells severely depend on the device architecture and the interface between each layer included in the device stack. In particular, the interface between the charge transporting layer and the perovskite film is crucial, since it represents both the substrate where the perovskite polycrystalline film grows, thus directly influencing the active layer morphology, and an important site for electrical charge extraction and/or recombination. Here, we focus on engineering the interface between a perovskite-polymer nanocomposite, recently developed by our group, and different commonly employed polymeric hole transporters, namely PEDOT: PSS [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)], PEDOT, PTAA [poly(bis 4-phenyl}{2,4,6-trimethylphenyl}amine)], Poly-TPD [Poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] Poly-TPD, in inverted planar perovskite solar cell architecture. The results show that when Poly-TPD is used as the hole transfer material, perovskite film morphology improved, suggesting an improvement in the interface between Poly-TPD and perovskite active layer. We additionally investigate the effect of the Molecular Weight (MW) of Poly-TPD on the performance of perovskite solar cells. By increasing the MW, the photovoltaic performances of the cells are enhanced, reaching power conversion efficiency as high as 16.3%.

Optical properties of molecular nanocrystals consisting of J-aggregates of anionic and cationic cyanine dyes

We report results of experimental studies of the photoabsorption, photoluminescent and photoelectric properties of a new type of multilayer molecular nanocrystals, consisting of highly ordered J-aggregates of one anionic and two cationic J-aggregates of cyanine dyes. In contrast to conventional J-aggregated dyes the multichromic nanocrystals synthesized in this work, are capable of efficient light absorption in three excitonic bands of the visible and near-IR spectral ranges. The spectral peak positions in the absorption bands can be controlled by appropriately selecting a set of dyes a molecular crystal is made of. Our investigations of the photoelectric properties of multichromic crystals have shown that each of them can potentially be used as a photosensitive layer of a photocell with photoconductivity in three peaks of excitonic absorption. The synthesized nanocrystals are attractive for the creation of thin-film organic photodetectors with a large photosensitive area and varied photoabsorption spectra, excitonic waveguides and for some other applications in organic and hybrid photonics and optoelectronics.

Nanocrystals of CuMSnS4 (M = In or Ga) for solar energy conversion applications

Quaternary MIMIIIMIVXVI4 (I-III-IV-VI4) chalcogenides obtained by cross-substitution of binary and ternary compounds remain relatively unexplored. We have for the first-time synthesized wurtzite and defect chalcopyrite phases of CuMSnS4 (M = In or Ga) in the form of nanocrystals. Optical measurements show that the CuMSnS4 (M = In or Ga) nanocrystals exhibit strong visible light absorption with band gap values between 1.15 and 1.4 eV, suitable for solar energy conversion applications.

Hysteresis-Free 1D Network Mixed Halide-Perovskite Semitransparent Solar Cells

The morphology of hybrid organic-inorganic perovskite films is known to strongly affect the performance of perovskite-based solar cells. CH₃ NH₃ PbI_3-x Cl_x (MAPbI_3-x Cl_x ) films have been previously fabricated with 100% surface coverage in glove boxes. In ambient air, fabrication generally relies on solvent engineering to obtain compact films. In contrast, this work explores the potential of altering the perovskites microstructure for solar cell engineering. This work starts with CH₃ NH₃ PbI_3-x Cl_x , films with grain morphology carefully controlled by varying the deposition speed during the spin-coating process to fabricate efficient and partially transparent solar cells. Devices produced with a CH₃ NH₃ PbI_3-x Cl_x film and a compact thick top gold electrode reach a maximum efficiency of 10.2% but display a large photocurrent hysteresis. As it is demonstrated, the introduction of different concentrations of bromide in the precursor solution addresses the hysteresis issues and turns the film morphology into a partially transparent interconnected network of 1D microstructures. This approach leads to semitransparent solar cells with negligible hysteresis and efficiencies up to 7.2%, while allowing average transmission of 17% across the visible spectrum. This work demonstrates that the optimization of the perovskites composition can mitigate the hysteresis effects commonly attributed to the charge trapping within the perovskite film.

2H-NbS2 film as a novel counter electrode for meso-structured perovskite solar cells

We report the use of 2H-NbS₂ film as a novel counter electrode in perovskite solar cells fabricated with a cold isostatic pressing method. The 2H-NbS₂ film, which was prepared through an exfoliation method followed by restacking from Li_xNbS₂ powder, shows high electrical conductivity of 8.7 × 10³ S cm⁻¹ and work function of 5.20 eV. The two-dimensional transition metal dichalcogenide was used for the first time as a counter electrode in meso-structured perovskite solar cells. Through this process, we demonstrated a new alternative to noble metals. The perovskite solar cell base on the 2H-NbS₂ counter electrode showed an open-circuit voltage of 1.046 V, comparable to that of gold, and a power conversion efficiency of 8.3%.

Large-area perovskite solar cells - a review of recent progress and issues

In recent years, perovskite solar cells (PSCs) have attracted great attention in the photovoltaic research field, because of their high-efficiency (certified 22.1%) and low-cost. In this review paper, we briefly introduce the history of efficiency development for PSCs, and discuss some of the major problems for large-area (≥1 cm2) PSC devices. In addition, we summarize the recent progress in the aspects of fabrication methods for large-area perovskite films, and improving the efficiency and stability of the large-area PSC devices. Finally, we give a short summary and outlook of large-area PSC devices. This article is mainly organized into three parts. The first part focuses on the main fabricating technologies for large-area perovskite films. The second section discusses some methods that are used to improve the efficiency of PSCs. In the last part, different approaches are used to improve the stability of PSCs.

Fabrication of Semiconducting Methylammonium Lead Halide Perovskite Particles by Spray Technology

In this "nano idea" paper, three concepts for the preparation of methylammonium lead halide perovskite particles are proposed, discussed, and tested. The first idea is based on the wet chemistry preparation of the perovskite particles, through the addition of the perovskite precursor solution to an anti-solvent to facilitate the precipitation of the perovskite particles in the solution. The second idea is based on the milling of a blend of the perovskite precursors in the dry form, in order to allow for the conversion of the precursors to the perovskite particles. The third idea is based on the atomization of the perovskite solution by a spray nozzle, introducing the spray droplets into a hot wall reactor, so as to prepare perovskite particles, using the droplet-to-particle spray approach (spray pyrolysis). Preliminary results show that the spray technology is the most successful method for the preparation of impurity-free perovskite particles and perovskite paste to deposit perovskite thin films. As a proof of concept, a perovskite solar cell with the paste prepared by the sprayed perovskite powder was successfully fabricated.