Solar Cell Fabrication Process Research Articles

Application of non-contact quantum efficiency measurement for solar cell fabrication process insights

We demonstrate the application of non-contact external quantum efficiency (EQE) measurements as potential in-line inspection for solar cell mass production. The technique, based on electroluminescence excitation spectroscopy (ELE), is several times faster than conventional contacted EQE measurements, and enables on-the-flight contactless assessment of spectral response. To simulate a manufacturing environment, EQE of a batch of 200 bifacial PERC solar cells are investigated. This allows statistical analysis of the interplay between fabrication process conditions, cell current–voltage characteristics and results from other in-line inspection tools. The study shows that non-contact EQE can be used to detect variation in POCl3 diffusion and PECVD processes at cell level and without direct contact to the device. It is also possible to predict EQE on passivated, non-metallized diffused wafers. This provides powerful information in predicting end-of-line cell parameters, as well as to sort and remove low performing wafers prior to printing to eliminate metal paste wastage.

Analysis of the ZnO/Cu2O and CdSe/Cu2O Thin Film Hetero-structure Electrode for Photo Electro chemical Solar Cell Applications

This paper proposes an economical route to the production of CdSe/Cu2O and ZnO/Cu2Obased on commercial ZnO, CdSe corpuscle. The deposition of CdSe thin films was prepared by partial thermal oxidation method, Powder Vaporization method, and microwave oven method on the cleaned Cu2O substrate at room temperature. The solar cell fabrication process is greatly simplified by this method and opens a door in the direction of inexpensive techniques based on saleable available materials. The results show that the solar cell based on the mixture of CdSe/Cu2O has electron transportability, better light absorption, and high power conversion efficiency (PCE) of 0.7 was obtained. These materials have been characterized using FTIR, at which numerous peaks are present in the sample, and were assessed in detail. Multiple current-voltage characteristic curves were plotted, an open-circuit voltage VOC, a short circuit current Isc, and the maximum power points Pmax were also noted. This work throws off more light in enhancing the photo response of the electrode in both solar H2generation and photo electro chemical solar cell

4-tert-butyl pyridine additive for moisture-resistant wide bandgap perovskite solar cells

Perovskite solar cells fabrication process need inert or low humidity atmospheres. While highly efficient perovskite solar cells to overcome the photovoltaic marketing should be achieved stability at any environmental conditions. At high humidity, water molecules react with the perovskite layer and increase the degradation rate, leading to a drastic decrease in device performance and perovskite crystallinity. In this work, the effect of environmental humidity on photophysical parameters of wide bandgap, (WBG) perovskite layer and solar cells stability is systematically investigated and tBP is proposed as an additive in perovskite precursor to increase the moisture resistance and improve the crystallinity of the perovskite film, which is fabricated and kept at 80% RH. tBP act as a surface modification of the perovskite layer. According to SEM, XRD and water contact angle analysis, the crystallinity and hydrophobicity of the perovskite film improve by utilizing tBP. The stability and efficiency of the perovskite solar cells with tBP additive are higher than the perovskite solar cells without tBP. This work demonstrates that the engineering of the absorber precursor with a suitable additive could be a simple and low-cost strategy to reduce the effect of moisture in perovskite devices at high relative humidity.

Thermally stable poly‐Si tunnel junctions enabling next‐generation high‐efficiency Si solar cells

AbstractWe demonstrate thermally stable polysilicon (poly‐Si)‐based tunnel junctions (TJs), that is, n+‐poly‐Si/p+‐poly‐Si/SiOx and n+‐poly‐Si/SiOx/p+‐poly‐Si/SiOx, for passivating a silicon wafer, selectively extracting holes, and being compatible with the high‐temperature firing process of screen‐printed metal contacts. An additional interfacial oxide between the n+‐poly‐Si and p+‐poly‐Si layers enhances thermal stability and acts as a barrier layer to mitigate dopant interdiffusion between the adjacent poly‐Si layers, without significantly increasing the contact resistance. The TJ's thermal stability is investigated by analysing the TJ recombination current density J0 and effective contact resistance ρc after high‐temperature firing (740°C to 840°C) of nonmetallised samples. We evaluate two different TJ applications via efficiency potential calculations: (1) When the TJ is applied on the front side of a passivated‐contact Si bottom cell for 2‐terminal tandem cells, a calculated add‐on efficiency of 9.9% for the Si bottom‐cell can be achieved with the inclusion of the interfacial oxide; (2) to enable conventional metal screen‐printing on a p+‐poly‐Si layer, the TJ is applied on the rear side of a single‐junction Si solar cell, giving a calculated cell efficiency potential of 23.6% at 1‐Sun condition. For such a configuration, in the absence of an interfacial oxide between the adjacent poly‐Si layers, the cell efficiency potential improves with peak firing temperature. In summary, we successfully develop thermally stable hole‐extracting TJs for the two aforementioned applications that are fully compatible with existing industrial silicon solar cell fabrication processes.

Properties of the mesoporous perovskite solar cell by plasma surface activation with a titanium dioxide electrode

Perovskite solar cells (PSCs) have attracted considerable attention as accessible solar cells due to its ease of fabrication, high energy-conversion efficiency, and low manufacturing costs. This study explores the effect of plasma treatment over time (10, 20, 30 min) on the mesoporous titanium dioxide layer. The solar cell fabrication process was investigated to enhance the efficiency of the power conversion of the PSCs. After modifying the interface between the electron transporting layer and the perovskite layer by plasma surface activation, the plasma surface activation characteristics on the TiO2 electrode were studied. The performance of the PSCs was also studied.

Advanced characterization methods of carrier transport in quantum dot photovoltaic solar cells

Solution-processed colloidal quantum dot (CQD) solar cells are lightweight, flexible, inexpensive, and can be spray-coated on various substrates. However, their power conversion efficiency is still insufficient for commercial applications. To further boost CQD solar cell efficiency, researchers need to better understand and control how charge carriers and excitons transport in CQD thin films, i.e., the CQD solar cell electrical parameters including carrier lifetime, diffusion length, diffusivity, mobility, drift length, trap state density, and doping density. These parameters play key roles in determining CQD thin film thickness and surface passivation ligands in CQD solar cell fabrication processes. To characterize these CQD solar cell parameters, researchers have mostly used transient techniques, such as short-circuit current/open-circuit voltage decay, photoconductance decay, and time-resolved photoluminescence. These transient techniques based on the time-dependent excess carrier density decay generally exhibit an exponential profile, but they differ in the signal collection physics and can only be used in some particular scenarios. Furthermore, photovoltaic characterization techniques are moving from contact to non-contact, from steady-state to dynamic, and from small-spot testing to large-area imaging; what are the challenges, limitations, and prospects? To answer these questions, this Tutorial, in the context of CQD thin film and solar cell characterization, looks at trends in characterization technique development by comparing various conventional techniques in meeting research and/or industrial demands. For a good physical understanding of material properties, the basic physics of CQD materials and devices are reviewed first, followed by a detailed discussion of various characterization techniques and their suitability for CQD photovoltaic devices.

Inverted planer perovskite solar cells fabricated by all vapor phase process

A simple vapor-based fabrication process for perovskite solar cells is developed and applied to the fabrication of inverted planar CH3NH3PbI3 (MAPbI3) perovskite solar cells. In this process, PbI2 film is deposited by vacuum evaporation on the hole transport layer (HTL), followed by converting it into the MAPbI3 phase by annealing in methylammonium iodide (MAI) vapor. Using the converted MAPbI3 films, we fabricated inverted planar perovskite solar cells by vapor phase-based process with a device structure of glass/TCO/HTL/MAPbI3/C60/BCP/Ag, in which PEDOT:PSS and copper phthalocyanine (CuPc) were used as an HTL. A power conversion efficiency as high as 16.1% was obtained for the solar cell using CuPc as an HTL by a fully vapor-based process. Furthermore, we observed the improvement of the stability of the solar cells when using CuPc instead of PEDOT:PSS as an HTL.

Oxygen Precipitation Behavior in n-Type Cz-Si Related to Carbon Concentration and Crystal Growth Conditions

The behavior of oxide precipitates during solar cell fabrication processes and the resulting effect on device performance have been investigated by transmission electron microscopy (TEM) observation. Samples were prepared with different carbon concentration and under different crystal growth conditions, namely using the conventional and an advanced process. The density of oxide precipitates increased monotonically with the carbon concentration, while the cell efficiency improved with decreasing oxygen precipitate density. When the carbon concentration was reduced to below 1016 cm−3, the oxide precipitates grew largely and dislocations were introduced. TEM observations confirmed that the morphology of the oxide precipitates clearly differed depending on the crystal growth conditions. Precipitates grown in platelet form introduced high density dislocations in their surroundings, while the dislocation density was relatively lower around polyhedral-type precipitates. These results thus reveal that oxygen precipitation can be controlled by varying the crystal growth conditions, possibly contributing to the production of high-efficiency solar cells.

Perovskite/silicon heterojunction tandem solar cells: Advances in optical simulation

Perovskite/silicon heterojunction tandem solar cells have developed rapidly in recent years, and their efficiency is enhanced from 13.7% to 29.1%. As is well known, the optical loss has a great influence on the efficiency. Due to the complex fabrication process of tandem solar cells, it is important to obtain high-performance tandems through optical simulation. In this paper, optical simulation methods are mainly summarized from two aspects: commercial software and self-built model. Then, the progress of optical simulation is analyzed in terms of reflection loss and parasitic absorption. Finally, what should be paid more attention to in the optical simulation of tandem solar cells is pointed out. The efficiency limit of perovskite/silicon heterojunction tandem solar cells can reach up to 40%, but there remains much room for improvement. The research on optical simulation will lay the foundation of developing the tandem solar cells.

Modeling and optimization of the fabrication process of thin-film solar cells by multi-source physical vapor deposition

This work presents a mathematical model describing the thin film formation during the co-evaporation of elements by PVD process for the production of CIGS type thin film photovoltaic cells. We propose a one-dimensional system of cross-diffusion Partial Differential Equations (PDEs) defined in a time-dependent space domain and introduce a numerical scheme for the discretization of the system. We calibrate our model on true experimental measurements using a dual approach. Then, in order to achieve certain targeted final concentration profiles, we consider an optimization problem that allows controlling the external atomic fluxes injected during the process. Despite its simplicity, the proposed model shows promising results towards a quantitatively predictive model. For instance, novel atomic fluxes obtained as solutions of the optimization problem could represent alternatives to the classical three-stage process. In this paper, a mathematical model describing the thin film formation during the co-evaporation PVD process for the production of CIGS type thin film photovoltaic cells is proposed.

Floating Gate Schottky Junction Solar Cells With Improved Output Power

In this article, the concept of floating gate Schottky junction (FGSJ) solar cell with improved photovoltaic properties, compared to those of the conventional Schottky junction solar cell, is proposed. The floating gate junction is electrically isolated from the current collection junction in order to prevent reduction in the barrier height at the floating gate contact from load voltage. The unaffected barrier height at the floating gate junction leads to a more effective separation of photo-generated electron-hole pairs, and therefore, a better photovoltaic response. Single junction FGSJ solar cells based on n -type GaAs with different doping concentration levels and gate contact layer materials were fabricated, and their electrical and optical properties were characterized under standard 1-sun illumination condition. The measurement results show a notable improvement in both diode-like and photovoltaic properties of FGSJ solar cells compared to those of the conventional Schottky solar cells, which includes higher short-circuit current density, open-circuit voltage, and maximum output power. This is due to a higher equivalent Schottky barrier height in FGSJ solar cells compared with nonfloating gate devices. Moreover, the proposed floating gate structure can be used in metal/ n -type semiconductor Schottky junctions to eliminate the use of highly p -doped wide bandgap semiconductors in p–n junctions. Also, the simpler and more cost-effective fabrication process of the FGSJ solar cells, compared to the p–n junction solar cells, could reduce the total production cost; therefore, making them financially viable for large-scale development of high-efficiency photovoltaic panels.

Evaluation of plasma induced defects on silicon substrate by solar cell fabrication process

This research investigates the cause of lifetime reduction properties of a crystalline defect layer introduced by the plasma process such as reactive plasma deposition (RPD). The plasma irradiation damage to silicon substrate with the different oxygen and carbon concentrations were evaluated. Minority carrier lifetime of the silicon substrate after the RPD process has been significantly reduced by plasma irradiation. Furthermore, photoluminescence (PL) spectroscopy revealed that the cause of the lifetime degradation on the silicon substrate is Ci–Oi defect generation originated in the plasma irradiation during the RPD process.

Impact of Al Doping on Surface Passivation of TiOx on Si

Titania (TiOx) is re-emerging to be a passivating material for the surfaces of high-efficiency crystalline silicon solar cells. Numerous sources in the literature suggest that the surface passivation and thermal stability of TiOx deteriorates with increasing film thickness when the TiOx film is thicker than a sufficient thickness. To circumvent this limitation, this study presents a novel process of Al-doped TiOx (TiOx:Al) film, which demonstrates the potential for improved thermal stability and surface passivation. Based on grazing incident X-ray diffraction and UV-Raman measurements, the incorporation of Al impurity in TiOx effectively restrains the crystal phase transformation of the amorphous TiOx layer during deposition. Furthermore, the TiOx:Al films provide better thermal robustness up to 350 °C, which makes it highly compatible with Si solar cell fabrication processes.

Fabrication and degradation performance analysis of perovskite solar cells

Methyl–ammonium lead–halide perovskites are acknowledged as highly promising materials for photovoltaic applications.The popularity of these materials is due to the high efficiency of ready photovoltaic devices comparable to the efficiency of industrial silicon solar cells as well as the possibility of significant reduction in production cost. Perovskite materials have a straight and narrow bandgap, as a result of which they have a high light absorption efficiency comparable to silicon;  and to obtain solar cells requires a thin layer of a solution obtained from solutions, which significantly reduces the production of solar cells from perovskite. The fabrication process for perovskite solar cells is rather simple and does not require high temperatures. Also, the ease of manufacturing of laboratory samples gives an opportunity to develop this technology with low capital expenditures and to join to the global research and trends in this field. The paper describes the results of fabrication and study of degradation under the influence of external factors, the atmosphere of perovskite films and solar cells obtained at a temperature of 100° C by centrifugation, which makes it possible to apply uniform films with a thickness of several nanometers to several microns easy and quickly. Key words: alternative energy, photovoltaics, perovskite solar cells.

<i>γ</i>-Ray Irradiation Effect on MCF Rubber Solar Cells with both Photovoltaics and Sensing Involving Semiconductors Fabricated under Magnetic and Electric Fields

For cases in which a robot with installed solar cells and a sensor operates in a nuclear reactor building or in space for extravehicular activity, we require elastic and extensible solar cells. More than two different types of sensing are also required, minimally with photovoltaics and built-in electricity. Magnetic compound fluid (MCF) rubber solar cells are made of rubber, so they are elastic and extensible as well as sensitive. To achieve flexibility and an effective photovoltaic effect, MCF rubber solar cells must include both soluble and insoluble rubbers, Fe3O4, TiO2, Na2WO4∙2H2O, etc. On the basis of this constitution, we propose a consummate fabrication process for MCF rubber solar cells. The characteristics of these cells result from the semiconductor-like role of the molecules of TiO2, Fe3O4, Ni, Na2WO4∙2H2O, polydimethylsiloxane (PDMS), natural rubber (NR), oleic acid, polyvinyl alcohol (PVA), water and magnetic cluster involved in the MCF rubber. Their tendencies can be deduced by synthesizing knowledge about the enhancement of the reverse-bias saturation current IS and the diode ideality factor N, with conventional knowledge about the semiconductor affected by γ-irradiation and the attenuation of the photon energy of γ-rays.

Water, a Green Solvent for Fabrication of High-Quality CsPbBr3 Films for Efficient Solar Cells.

Water has been labeled as a devil in fabrication and stability of perovskite solar cells. The inherent cognition impels researchers to prepare perovskite films in water-controlled conditions. Herein, water is used as a green solvent to prepare CsPbBr3 films through a two-step spin-coating method. Due to the high solubility of CsBr but low solubility of PbBr2 in water, it provides a possibility to deposit CsBr onto PbBr2 from water solution without destroying the film. Here, high-quality CsPbBr3 films are fabricated by spin-coating concentrated CsBr/H2O solution onto the PbBr2 film followed by annealing. As a result, the solar cells basing on a configuration of FTO/TiO2/CsPbBr3/Carbon exhibit a power conversion efficiency of 6.12%. This work provides a simple and easy way to prepare high-quality CsPbBr3 films for efficient solar cells. It makes a solid step toward reducing the solvent toxicity in the fabrication process of perovskite solar cells. It also breaks the forbidden zone for fabricating perovskite films from water and updates the inherent understanding of water in the research study of perovskite solar cells.

Real-Time Electron Nanoscopy of Photovoltaic Absorber Formation from Kesterite Nanoparticles

Cu2ZnSnS4 nanocrystals are annealed in a Se-rich atmosphere inside a transmission electron microscope. During the heating phase, a complete S-Se exchange reaction occurs while the cation sublattice and morphology of the nanocrystals are preserved. At the annealing temperature, growth of large Cu2ZnSnSe4 grains with increased cation ordering is observed in real-time. This yields an annealing protocol which is transferred to an industrially-similar solar cell fabrication process resulting in a 33% increase in the device open circuit voltage. The approach can be applied to improve the performance of any photovoltaic technology that requires annealing because of the criticality of the process step.

Weatherability of Cu2ZnSnSe4 thin film solar cells on diverse substrates

This paper presents a thorough investigation over characteristics and device performance of Cu2ZnSnSe4 (CZTSe) thin films and CZTSe solar cells prepared on Mo substrate, and on transparent oxide layers including SnO2:F (FTO) layer, and In2O3:Sn (ITO) layer. The resultant CZTSe thin film is characterized by X-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), field emission scanning electron microscope (FESEM), and photoluminescence (PL), and is subsequently fabricated into CZTSe solar cell. The characterization measurements have unveiled that, different substrate material can affect the diffusion of sodium and zinc, hence alters the distribution of ZnSe, surface morphology and crystalline structure of the CZTSe thin film. In comparison, FTO shows superior stability among Mo substrate and ITO substrate during high temperature fabrication process for CZTSe thin film solar cells. For weatherability test of the three CZTSe solar cells with different substrates, all of the three devices have also been exposed to damp heat damage. Test results shows the least efficiency decline on the CZTSe solar cell with FTO substrate after damp heat damage, suggesting that the CZTSe solar cell with FTO substrate is the most resistive to damp heat weathering. The CZTSe solar cell with Mo substrate can be deteriorated at Mo substrate layer and shows more drastic efficiency decrease. The comparison reflects a high potential in CZTSe solar cell for the next generation photovoltaic applications, such as see-through solar cells and building-integrated photovoltaic (BIPV).

Characterizing Point Contacting by Localized Dielectric Breakdown and Its Use in Silicon Solar Cell Applications

The point contacting by localized dielectric breakdown (PLDB) method utilizes a dielectric breakdown above a locally doped region to form ohmic contacts for a solar cell rear surface. This article describes the design and fabrication of the PLDB solar cells and the contact properties characterization. A complete solar cell fabrication process applying PLDB as a rear contact design was developed, with the demonstration of an 18.0% proof-of-concept PERC structure PLDB solar cell. Two major loss mechanisms in the fabricated solar cell were characterized to be a high series resistance and nonideal recombination. By modulating the local boron doping profile with acidic etching, the impact of the surface doping concentration on local contact recombination and contact resistivity was investigated, resulting in an estimated contact resistivity of approximately 5 mΩ·cm2 and contact recombination of approximately 600 fA/cm2. With these metrics, modeling suggests that by optimizing the contact pitch of our solar cells, efficiencies of up to 24% are well achievable for this low-temperature contacting method.

Vacuum-free fabrication of high-performance semitransparent perovskite solar cells via e-glue assisted lamination process

From a base material of conductive polymer (poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS), a flexible and high-conductivity (as low as 45 Ω/sq) transparent electrode was fabricated on polydimethylsiloxane elastomer by an acid treatment and transfer process. Combined with the D-sorbitol-doped PEDOT:PSS electric glue, we successfully demonstrated a vacuum-free and ambient lamination fabrication process for semi-transparent perovskite solar cells using triple cation Cs005(MA017FA083)095Pb(I083Br017)3 perovskite. By this manufacturing-friendly lamination process, we fabricated semi-transparent perovskite solar cell devices with power conversion efficiencies up to 16.4% and variable transparencies.