Solar Cell Absorber Research Articles

Two-stage growth of Cu3BiS3 thin films: Influence of the Cu/Bi ratio

Thin films composed of Cu3BiS3 have shown significant promise as light-harvesting materials because of their suitable optoelectronic properties and abundant, non toxic constituent elements. A large-grained, highly crystalline Cu3BiS3 films is a prerequisite for application of these layers in solar cells. We have grown large-grained, highly crystalline Cu3BiS3 films by a two-stage process via thermally evaporating Cu/Bi/Cu metallic layers and sulfurization at 400 °C for 30 min. The influence of the Cu/Bi ratio on the growth of Cu3BiS3 thin films was investigated by varying the Bi precursor thickness. The Cu/Bi ratio significantly influenced the structural, microstructural, optical, and electrical properties of Cu3BiS3 thin films. The Cu3BiS3 film synthesized with a Cu/Bi ratio of 4.35 contained Cu1.8S spurious phase, a non-uniform grain morphology, a direct optical bandgap of 1.41 eV, and an electrical resistivity of 75.5 Ωcm. Upon decreasing the Cu/Bi ratio from 3.38 to 2.77, the Cu1.8S spurious phase was eliminated, and phase-pure Cu3BiS3 was crystallized with a uniform grain morphology, particle size of 2–4 μm, direct bandgap of 1.42 eV, and electrical resistivity of 53.5 Ωcm. A further decrease in the Cu/Bi ratio from 2.77 to 2.54 resulted in a slight decrease in the grain size and electrical resistivity of the Cu3BiS3 films. This study demonstrates that Cu3BiS3 films synthesized with near-stoichiometric composition possess better structural, microstructural, optical, and electrical properties than those synthesized with Cu-rich composition and are suitable for use as solar cell absorber layer.

Manipulating Nucleation and Crystal Growth of Inorganic Perovskite Solar Cells.

Inorganic metal halide perovskite materials as sunlight absorbers for solar cells exhibit better thermal stability than organic-inorganic hybrid counterparts. Pure cesium lead triiodide (CsPbI3), with the most suitable band gap, suffers phase instability under an ambient environment. Nucleation and crystal growth are two crucial steps in fabricating a solution-processed perovskite film. A high-quality perovskite film with good morphology makes a significant impact on the efficiency and stability of perovskite solar cells. Dimethylformamide (DMF) is a commonly used aprotic solvent. However, it is difficult to obtain a high-quality inorganic perovskite film using DMF as a single solvent due to its slow evaporation and strong coordination with Pb2+. Here, we investigate dimethylacetamide (DMAc)/DMF as a cosolvent to prompt nucleation during the spin-coating process, leading to higher nucleation density and better surface coverage. In addition, we introduce CsBr in dimethylammonium lead triiodide (DMAPbI3)/CsI precursors to slow down the crystal growth process. CsBr does not increase the film band gap but leads to a pinhole-free film with better crystallinity. Through nucleation and crystal growth engineering, the power conversion efficiency of inorganic perovskite devices is improved to 17.67%, and ambient environment stability is significantly enhanced.

Potassium tin mixed iodide-bromide KSn(I1-xBrx)3 [x = 0.25,0.5,0.75,1] perovskites for solar cell absorbers: A computational study

Metal-halide perovskite (PVK) materials have been the subject of investigation in the photovoltaic community because of their remarkable optoelectronic characteristics. Nonetheless, the extrinsic and intrinsic instabilities of PVK materials remain a major obstacle to their commercial fabrication prospects. This problem can be resolved through halide mixing. In the current study, we examine the elastic, structural, mechanical, thermal, electronic, optical, and thermoelectric properties of potassium tin mixed iodide-bromide(I-Br) PVK, KSn(I1-xBrx)3 [x = 0.25, 0.5, 0.75, 1] (KSnIBr). With an increase in bromine concentration, KSnIBr’s thermodynamic stability is found to rise. The elastic properties demonstrate the mechanical stability of the PVK materials. The Pugh’s ratio, Cauchy’s pressure, and Poisson’s ratio highlight their ductility. Ductile materials are desirable for the formation of thin films. An extremely high melting point ensures that the PVK materials retain their solid state even at very high temperatures. The high absorption coefficient (αω), low energy loss factor (L(ω)), and low reflectivity(R(ω)) in the visible region are used to pitch their candidature as absorber materials in perovskite solar cells (PSC). A bandgap (Eg) of 1.9 eV, 1.9608 eV, 1.9761 eV, and 2.1285 eV is obtained for KSn(I0.75Br0.25)3, KSn(I0.5Br0.5)3, KSn(I0.25Br0.75)3, and KSnBr3 respectively. A single junction perovskite solar cell utilizing the KSnIBr perovskite is simulated using SCAPS software. An efficiency of 11.31 %, 10.3 %, 9.89 %, and 8.05 % are reported for KSn(I0.75Br0.25)3, KSn(I0.5Br0.5)3, KSn(I0.25Br0.75)3 and KSnBr3 PVK respectively. These wide bandgap perovskite materials in conjunction with other narrow bandgap materials may be beneficial for the design of tandem solar cells in future.

The Structural, stability, electronic and optoelectronics properties of Y2AgBiX6 (Y = K, Na, li; X = I, Br, Cl) halide double Perovskites: A First-Principles study

The crystal structure, electronic and optoelectronic properties of halide double perovskites Y2AgBiX6 (Y = K, Na, Li; X = I, Br, Cl) have been studied by first principles (FPs) in this paper. According to the elastic modulus and formation energy of crystal Li2AgBiX6, its structural stability is poor. In addition, the dependence of their electronic and mechanical properties, the effective mass of carriers and light absorption on elemental composition has been analyzed, and it is inferred that these materials have good electron transport properties. The photovoltaic characteristics of halide perovskite materials (PMs) based on potassium and sodium are studied. The photovoltaic properties of perovskite films with thickness of 1 μm, 5 μm and 10 μm were further analyzed, and it was found that the absorption was the highest when the film thickness was 10 μm. The current–voltage curve of the solar cell with above perovskite as absorbing material is calculated and analyzed by first principles. The result shows that Na2AgBiBr6, Na2AgBiCl6, K2AgBiI6 and K2AgBiCl6 are predicted to have excellent photovoltaic properties. Compared to other commonly used PMs, perovskite Y2AgBiX6 (Y = K, Na, Li; X = I, Br, Cl) has a smaller effective mass, which may contribute to good carrier transport and high performance of its optoelectronic devices. The absorption curves of K2AgBiBr6, K2AgBiCl6, Na2AgBiBr6, Li2AgBiBr6, and Li2AgBiCl6 matched well with the spectral irradiance of AM 1.5. Taken together, K2AgBiBr6 and Na2AgBiBr6 are the most suitable candidates for solar cell absorption layers because of their appropriate band gap and good stability.

Substitution effects on physical and chemical properties of Cu2Fe1-xCoxSnS4 thin films synthesized by the sol-gel technique

The impact of iron and cobalt substitution on the structural, morphological and optical properties of the copper iron cobalt tin sulfide Cu2Fe1-xCoxSnS4 thin films was studied. Employing the simple and easy sol-gel spin-coating technique on soda-lime glass substrates without sulfurization phase, Cu2Fe1-xCoxSnS4 (x = 0, 50 and 100%) compound was formed with the (112) preferential orientation for all thin films in the tetragonal stannite structure at space-group I42 m. By performing X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy, Energy Dispersive analysis and UV–Vis–NIR spectrophotometry, the physical and chemical properties were examined. The substitution was observed to provide a slight variation of the lattice parameters. The crystallite size was found to vary between 14 and 32 nm and decreased by increasing the cobalt content. The Raman spectra confirm the result of the XRD via the appearance of two peaks located at 321 and 284 cm−1, corresponding to the A1 vibration mode. The morphological analysis showed homogenous film surfaces. Optical characterizations showed that all thin films exhibit a band-gap energy, estimated between 1.1 and 1.53 eV, with an absorption coefficient greater than 104 cm−1. The possible use of thin films as an absorber for solar cells, with an adjustable optical band gap is proven.

Self-passivated CdS buffer layer for antimony sulfide solar cells

Sb2S3 has been paid extensive attentions as absorber for solar cells. Comparing with some oxides, CdS exhibits excellent compatibility to Sb2S3 therefore is most commonly used as buffer layer (BL) materials for Sb2S3 solar cells. Proper passivation can enhance the performance of CdS buffer layer thus raising the performances of Sb2S3 solar cells. Herein, we put forward a self-passivation strategy to enhance the performance of CdS by a two-step deposition process to fabricate the self-passivated CdS BL. First, we adopted spin coating combined with annealing process to prepare flaked CdS on FTO, then we performed passivation process to the CdS by depositing another layer of CdS with chemical bath deposition (CBD) method. After Sb2S3 was deposited on the self-passivated CdS by hydrothermal method, a solar cell with FTO/CdS (∼90 nm)/Sb2S3 (160 nm)/Spiro-OMeTAD(48 nm)/Ag(32 nm)structure was obtained by deposition of hole transport layer and Ag electrodes. Comparing with the single spin-coating processed CdS BL or single chemical bath deposited CdS BL, the self-passivated CdS presents better performance. The CBD process presents distinctive passivation effects to the first layer. In consequence, we obtained the highest PCE of 6.04 % in the Sb2S3 solar cells on the self-passivated CdS BL. The present work supplies a unique route to enhance the performances of CdS buffer layer.

Scrutinizing the effect of substrate temperature and enhancing the multifunctional attributes of spray deposited copper gallium sulfide (CuGaS2) thin films

ABSTRACT Polycrystalline chalcopyrite CuGaS2 thin films were prepared using a spray pyrolysis route has been considered a potential material for the solar cell absorber layer. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) studied the impact of substrate temperature in the range of 200–300˚C on surface profile and roughness. Powder X-ray diffraction disclosed that the films were polycrystalline at all examined substrate temperatures, with crystallite size increasing with increased substrate temperature. The UV-Vis displays the cut-off wavelength in 550–880 nm for varied substrate temperatures of CuGaS2 thin films, and the observed band gap is 2.75 eV–1.89 eV. The electrical attributes showed the enhancement in mobility (4.632 cm2 V−1 s−1) for varied substrate temperatures of CuGaS2 thin films. The 300˚C temperature sprayed CuGaS2 polycrystalline films are a decent candidate to be apposite as an absorber layer in thin film photovoltaic solar cells.

A periodic corrugated metallic nanomesh for broadband light absorption enhancement

Plasmonic nanostructures have been demonstrated for their application in thin film solar cells to enhance absorption. Of particular concern is the novel design, enabling the broadband absorption enhancement. Here, we proposed and implemented a periodic corrugated Au nanomesh for broadband light absorption enhancement. By combining plasmon treatment of pre-stretched substrate and nanosphere lithography, the Au nanomesh on the nanocorrugation with different period has been realized. Compared to the planar nanomesh, the periodic corrugated nanomesh exhibits observable absorption enhancement at broad wavelength range, especially from 700[Formula: see text]nm to 1000[Formula: see text]nm, which is of significance in bring solar energy up to more utilization due to poor absorption of thin film solar cells at the near-infrared band. The enhancement attributes to the spatially geometry deformation of nanomesh supported more plasmonic resonance at the different adjacent frequency. Also, the absorption enhancement is relative to the period of corrugation, which caused by the variation of geometry deformation amplitude of nanomesh. This periodic corrugated metallic nanomesh provides an alternative nanostructured electrode to broadband absorption enhancement for thin film solar cell application.

High-efficiency n-TOPCon bifacial solar cells with selective poly-Si based passivating contacts

Improving the conversion efficiency of n-TOPCon solar cell is still a hot topic. The selective poly-Si based passivating contacts (Poly-SEs) are ideal candidates for reducing the parasitic absorption and contact resistivity of n-type silicon solar cells and for providing better current collection. In this work, we used LPCVD and the POCl3 tube furnace diffusion methods to fabricate the selective poly-Si based passivating contacts, and studied the influences of key process parameters of the SiOx layer formation process (the oxidation duration (toxidation) and the constant pressure duration (tpressure)), and POCl3 tube diffusion process parameters (the POCl3-N2 carrier gas flow rate at the deposition, deposition temperature, drive-in temperature) on the n+-poly-Si profiles, recombination current density (J0), contact resistivity (ρc) of n-TOPCon solar cells. The results showed that the toxidation and tpressure had a significant impact on J0 and ρc which were mainly related to the distribution number of O and Si4+ content on the growth of the SiOx layer. And the influence of the drive-in temperature of phosphorus (P) diffusion process on J0 value is stronger than that of the deposition temperature, which was mainly related to the chemical passivation of SiOx layer induced by P-indiffusion into Si at high temperature. The reduction in the thickness of poly-Si from 110 nm to 30 nm led to an increase in the short-circuit current density (Jsc) per nanometer of ∼0.0093 mA/cm2 per nm. The Poly-SEs were fabricated by 3D printing mask technology and secondary LPCVD/phosphorus diffusion with J0, n+ ≈ 5 fA/cm2 (n+-poly-Si layer ≈ 50 nm) and J0, metal,n++ ≈ 73.8 fA/cm2 (n++-poly-Si layer ≈ 110 nm), and the efficiency was improved by 0.12% owing to the increase in Jsc value of 0.28 mA/cm2. After optimizing the passivation process, the industrial-grade TOPCon bifacial cells reached an efficiency (Eff), Voc, Jsc, and FF values as high as 25.4%, 721 mV, 42.2 mA/cm2, and 83.5%, respectively.

Device modeling and numerical study of a double absorber solar cell using a variety of electron transport materials

In photovoltaic (PV) technology, halide perovskites are the prospective choice for highly efficient solar absorbers because of their superior optical properties, enhanced efficiency, lightweight, and low cost. In this study, a double absorber solar device using an inorganic perovskite called NaZn0.7Cu0.3Br3 as the top absorber layer and MASnI3 as the bottom absorber layer is analyzed utilizing the SCAPS-1D simulation tool. The primary goal of this study is to look for a device architecture with a higher efficiency level. Here, current matching over two active layers is performed by adjusting the thickness of both active layers. This research focuses on the effect of various electron transport layers, varied absorber layer thicknesses, temperatures, absorber defect density, and metalwork functions on the performance of the proposed photo-voltaic cells. After researching a variety of solar cell architectures, it is revealed that FTO/ZnO/ NaZn0.7Cu0.3Br3 / MASnI3 / CuO /Au arrangement has an open circuit voltage of 1.1373 V, Fill Factor of 82.13%, short circuit current density of 34.71 mA/cm2 and highest power conversion efficiency (PCE) of 32.42%. Here, the simulations of the device indicated that a thickness of around 1 μm for the MASnI3 absorber was optimum. Additionally, the results of the simulations demonstrate that the efficiency of the device rapidly drops with increasing absorbers defect density and temperature, and device structures are steady at 300 K. Finally; any conductor can make the anode if its work function is larger than or equal to 5.10 eV.

Investigation of the potential solar cell application of Cs2AgBiBr6 lead-free double perovskite

Methylammonium lead halides are outstanding photoactive perovskites for energy conversion devices. Irrespective of excellent performance, chemical instability, and toxicity remain challenges for their potential acceptance. Recently, owing to the nontoxicity and high relative stability of Cs2AgBiX6 (X = Cl or Br), double perovskites have found as a significant substitution to the lead-based absorber for perovskite solar cells (PSCs). Especially, Cs2AgBiBr6 has appeared to be an alternative to perovskite based on lead. The unique features of Cs2AgBiBr6 like nontoxicity, higher stability, multifunctionality, and optoelectronic properties lead to promising lead-free double perovskite. In this study, the potential solar cell application of lead-free Cs2AgBiBr6 double perovskite absorber is studied through density functional theory and via experimental and theoretical analysis. SACPS-1D simulation is used to design a PSC of FTO/SnO2/Cs2AgBiBr6/Cu2O/Au cell configuration to study the effect of various parameters. The device simulation is initially optimized and validated under the experimental counterpart and then the other parameters for the material such as the absorber thickness, defect density, operating temperature, series resistance, bandgap, etc are improved to deliver a better performance. Further, the suggested device simulation is performed with various electron transport layers (ETLs) of SnO2, TiO2, and ZnO revealing these ETLs may be adopted for PSCs composed of lead-free Cs2AgBiBr6 absorber. Final optimized Cs2AgBiBr6 has a power conversion efficiency of 16.63%, 16.85%, and 16.79%, open-circuit voltages of 1.511, 1.508, and 1.510 V, current densities of 15.76, 15.71 and 15.75 mA/cm2, and fill factors of 69.84, 71.1 and 72.52 with ETLs of SnO2, TiO2, and ZnO, respectively.

Enhanced absorption in perovskite solar cells byincorporating gold triangle nanostructures.

Perovskite has emerged as an outstanding light-absorbing material, leading to significant advancements in solar cell efficiency. Further improvements can be made by restructuring the internal optical properties of perovskite. In this study, we investigate the impact of gold triangle nanostructures on perovskite absorption rates, and we explore the optimization of surface plasmon resonance to enhance its solar absorption efficiency. Our numerical simulations revealed that stacking gold triangle nanostructures in the perovskite film resulted in a significant increase in its absorption rate. Finally, comparative testing showed that the solar spectral absorption rate of a 200nm thick perovskite film increased by 41.5%.

Optoelectronic property tuning of A2BX6(A = In, tl; B = Pd, pt; X = Cl, Br, I): A first-principles study

The structural stability, energy band and photoelectric properties of vacancy- ordered double halide perovskites A2BX6(A = In, Tl; B = Pd, Pt; X = Cl, Br, I) are studied in detail by first principles in this paper. The results show that these materials have suitable tolerance factor, negative formation energy and good phonon spectrum, which indicates that they have structural stability. These materials are all semiconductors with band gaps varying from 0.328 eV and 3.238 eV via HSE06 hybrid functional. All the materials have direct or quasi-direct band structures, which are beneficial for carrier generation. These materials have small reflectance and large absorption coefficients for visible - infrared light, especially in the ultraviolet region where the absorption coefficient is very large. The absorption coefficient of the material is obviously improved when the anion X changes from Cl to Br to I. Making a comprehensive analysis of absorption coefficient, transmittance and bandgap values, Tl2PdBr6 is regarded as a potential candidate for solar absorber in single junction solar cells, while In2PtCl6 and Tl2PtCl6 may be applied in transparent conductor films.

Alternative lead-free mixed-valence double perovskites for high-efficiency photovoltaic applications

Lead-based organic-inorganic hybrid perovskites have exhibited great potential in photovoltaics, achieving power conversion efficiencies (PCEs) exceeding 25%. However, the toxicity of lead and the instability of these materials under moist conditions pose significant barriers to large-scale production. To overcome these limitations, researchers have proposed mixed-valence double perovskites, where Cs2AuIAuIIII6 is a particularly effective absorber due to its suitable band gap and high absorptance efficiency. To further extend the scope of these lead-free materials, we varied the trivalent gold ion and halogen anion in Cs2AuIAuIIII6, resulting in 18 new structures with unique properties. Further, using first-principles calculations and elimination criteria, we identified four materials with ideal band gaps, small effective carrier mass, and strong anisotropic optical properties. According to theoretical modeling, Cs2AuSbCl6, Cs2AuInCl6, and Cs2AuBiCl6 are potential candidates for solar cell absorbers, with a spectroscopic limited maximum efficiency (SLME) of approximately 30% in a 0.25 μm-thick film. These three compounds have not been previously reported, and therefore, our work provides new insights into potential materials for solar energy conversion. We aim for this theoretical exploration of novel perovskites to guide future experiments and accelerate the development of high-performance photovoltaic devices.

A Novel Approach for Designing a Sub-Bandgap in CuGa(S,Te)2 Thin Films Assisted with Numerical Simulation of Solar Cell Devices for Photovoltaic Application.

As a well-explored chalcopyrite material, copper gallium sulfide CGS has been considered a potential material for solar cell absorber layers. However, its photovoltaic attributes still require to be improved. In this research, a novel chalcopyrite material, copper gallium sulfide telluride CGST, has been deposited and verified as a thin film absorber layer to fabricate high-efficiency solar cells by experimental testing and numerical simulations. The results display the intermediate band formation in CGST with incorporation of Fe ions. Electrical studies showed enhancement in mobility from 1.181 to 1.473 cm2 V-1 s-1 and conductivity from 2.182 to 5.952 S cm-1 for pure and 0.08 Fe-substituted thin films. The I-V curves display the photoresponse and ohmic nature of the deposited thin films, and the maximum photoresponsivity (0.109 A W-1) was observed for 0.08 Fe-substituted films. Theoretical simulation of the prepared solar cells was carried out using SCAPS-1D software, and the obtained efficiency displayed an increasing trend from 6.14 to 11.07% as the Fe concentration increased from 0.0 to 0.08. This variation in efficiency is attributed to the decrease in bandgap (2.51-1.94 eV) and the formation of an intermediate band in CGST with Fe substitution, which is evidenced in UV-vis spectroscopy. The above revealed results open the way to 0.08 Fe-substituted CGST as a promising candidate as a thin film absorber layer in solar photovoltaic technology.

Stabilized Perovskite Quantum Dot Solids via Nonpolar Solvent Dispersible Covalent Ligands.

The ligand exchange procedure of CsPbI3 perovskite quantum dots (PQDs) enables the fabrication of thick and conductive PQD solids that act as a photovoltaic absorber for solution-processed thin-film solar cells. However, the ligand-exchanged CsPbI3 PQD solids suffer from deterioration in photovoltaic performance and ambient stability due to the surface traps, such as uncoordinated Pb2+ sites on the PQD surface, which are generated after the conventional ligand exchange process using ionic short-chain ligands dissolved in polar solvents. Herein, a facile surface stabilization is demonstrated that can simultaneously improve the photovoltaic performance and ambient stability of CsPbI3 PQD photovoltaic absorber using covalent short-chain triphenylphosphine oxide (TPPO) ligands dissolved in a nonpolar solvent. It is found that the TPPO ligand can be covalently bound to uncoordinated Pb2+ sites and the nonpolar solvent octane can completely preserve the PQD surface components. Owing to their synergetic effects, the CsPbI3 PQD photovoltaic absorber stabilized using the TPPO ligand solution dissolved in octane exhibit higher optoelectrical properties and ambient stability than the control absorber. Consequently, CsPbI3 PQD solar cells composed of PQD photovoltaic absorbers fabricated via surface stabilization strategy provide an improved power conversion efficiency of 15.4% and an enhanced device stability.

Transmission electron microscopy studies of organic–inorganic hybrid perovskites: Advances, challenges, and prospects

In the last few years, organic–inorganic hybrid perovskites (OIHPs) have attracted immense research and industry attention for their application as light absorbers in solar cells and light-emitting diodes. Characterizing OIHP materials and optoelectronic devices using transmission electron microscopy (TEM)-based techniques has played a large role in understanding their structural, compositional, and electronic properties. However, the highly energetic and electrically charged electron beam radiation used in TEM can result in damage to the pristine structure, as OIHPs are unstable and highly sensitive to electron beams. This damage potentially obscures intrinsic information and leads to a serious misunderstanding of the microscopic structure–property–performance relationship for OIHP optoelectronic devices. To address this issue, we first review the electron and ion beam-induced degradation mechanism of OIHPs, followed by a review of the development of ultra-low-dose TEM techniques that can able to minimize this damage, thus can able to obtain reliable, intrinsic structural information about OIHPs from the atomic to micrometer length scales. Finally, we suggest a protocol for appropriate TEM specimen preparation and characterization techniques. This protocol can help ensure that future TEM studies of OIHPs give reliable information, thereby enabling a deeper understanding and optimization of the performance and long-term stability of OIHP optoelectronic devices.

Enhanced photostability of multication lead halide perovskites through the use of azaadamantane-based modifiers

Complex lead halides incorporating simultaneously a few univalent cations such as cesium (Cs+), methylammonium (MA+) and formamidinium (FA+) represent highly promising materials for perovskite solar cells, delivering record-high power conversion efficiencies. Unfortunately, these materials demonstrate insufficient stability, which limits their practical implementation; therefore, improving the photochemical and thermal stability of multication lead halide perovskites is an urgent task that needs to be addressed to achieve sufficiently long operational lifetimes of perovskite solar cells to facilitate their commercial real-life applications. Herein, we present a comparative study of two azaadamantane-based molecular modifiers as stabilizing additives for Cs0.10MA0.15FA0.75PbI3 and Cs0.12FA0.88PbI3 perovskite formulations. An iodide of N-methylated 1,3,5,7-tetraazaadamantane known as urotropine (MAdI) showed a modest stabilizing effect in Cs0.10MA0.15FA0.75PbI3, though it stabilized effectively Cs0.12FA0.88PbI3. On the contrary, 4,6,10-trihydroxy-3,5,7-trimethyl-1,4,6,10-tetraazaadamantane hydrochloride (NAdCl) strongly enhanced the stability of both lead halide perovskites and prevented the formation of metallic lead Pb0 as a photolysis product. Different stabilizing effects caused by MAdI and NAdCl were related to their different localization within the perovskite films, as evidenced by nanoscale infrared (IR) s-SNOM microscopy. Density functional theory (DFT) calculations confirmed the enhanced stability granted by NAdCl by demonstrating a much higher adsorption energy towards undercoordinated lead atoms on the surface of the perovskite. Finally, the optimal molecular modification of Cs0.10MA0.15FA0.75PbI3 and Cs0.12FA0.88PbI3 films with azaadamantanes made them completely tolerant to light and heat within at least 5000 and 16 000 h of aging, thus setting new perovskite stability records and presenting the newly-developed material formulations as highly promising absorbers for efficient and stable perovskite solar cells.

Development of phase pure Cu2ZnSiSe4 via solid state synthesis for energy applications

In recent years, quaternary diamond-like metal chalcogenide semiconductor nanocrystals have received a lot of attention in solar cell and thermoelectric applications. The optoelectronic properties of quaternary diamond-like structures are influenced by their crystal structure. In this work, a series of experiments have been performed to understand the crystal system of Cu2ZnSiSe4 materials via solid state synthesis, namely mechanosynthesis to get a single phase of quaternary chalcogenide via single step route synthesis. The materials were performed at different milling time to study the single phase compound and phase transformation of the materials. Based on the theory and existing literature, the composition of the materials has been selected as 2:1:1:4 which is the optimum composition for quaternary chalcogenides. Based on the composition, the material properties will be changed. X-ray diffraction (XRD) and Raman spectroscopy were used to analyse the structure and phase purity of Cu2ZnSiSe4 nanoparticles. Field emission scanning electron microscopy (FESEM) and Energy dispersive X-ray spectroscopy (EDS) results showed that the average size of the Cu2ZnSiSe4 particles and the composition of products were close to the stoichiometry of Cu2ZnSiSe4. Optical studies show that Cu2ZnSiSe4 nanocrystals exhibit good, strong optical absorption in the visible region of the electromagnetic spectrum and a 1.12 eV bandgap. Hall measurement shows the bulk property of the materials and it is inferred that the synthesized materials show p-type conductivity in bulk. The obtained compound possesses good structural and optoelectronic behavior and hence could be utilized as effective solar absorber in thin film solar cells.

Modelling and numerical simulations of eco-friendly double absorber solar cell “Spiro-OmeTAD/CIGS/MASnI3/CdS/ZnO” and its PV-module

A broad study for design of higher efficiency modules based on low-cost, non-toxic Au/Spiro-OmeTAD/CIGS/MASnI3/CdS/ZnO/FTO tandem configuration solar cells has been conducted using solar cell capacitance simulator package “SCAPS-1D”. For the cause of highly efficient device performance, the selection of suitable layer materials such as “ZnO” as electron transport layer “ETL”, “CIGS” and “MASnI3→CH3NH3SnI3” as absorber, “Spiro-OmeTAD” as hole transport layer “HTL”, and CdS as active buffer layer material have been developed. The structural layout of the recommended composition was enhanced by variation in thickness of the specified layers, different back contact layers and temperature. The power conversion efficiency “PCE” was found to be 36.38%, along with other electrical parameters such as short-circuit current density “Jsc” of 48.28 mA/cm2, open-circuit voltage “Voc” of 1.38 V, and fill factor of 54.24% for optimized layer thickness of 0.084 μm for “HTL”, 0.051 μm for ETL”, 0.028 μm for buffer layer, 2.10 μm and 1.51 μm for CIGS and CH3NH3SnI3 absorber layers respectively. The overall device performance in perspective of charge carrier generation and recombination was investigated in depth. The improvement of diffusion length has increased the charge carrier's generation around 3.69 μm and the recombination rate was found at a lower value of 2.2 μm which overall enhance the device performance. At standard conditions, the formation of supplementary electron-hole pairs by varying the absorber layers thickness shows the maximum extent for Jt, FF% and PCE% during optimized investigation. A module of dimensions (2.2 × 1.1) m consisting of 72 cells in series was configured in PVsyst software to get the panel performance. Input parameters obtained through solar capacitance simulator were incorporated to evaluate module performance and output power by variation in solar irradiation and temperature. Yearly performance ratio for home location has been explored and reported.