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8th World Conference on Photovoltaic Energy Conversion; 241-246, The production of uniform layers without defects is crucial for the efficient upscaling of perovskite solar cells. To understand the origin of defects and their impact on efficiency, we compare steady-state (DC) and alternating current (AC) measurements with simulation results obtained by an electro-thermal 2D+1D finite element method (FEM) implemented in the software Laoss. The software supports the upscaling process from small- to large-area devices by solving for the potential and temperature distribution in 2D top and bottom electrode domains, which are coupled by a vertical 1D coupling law. Recently, we extended this FEM model to the frequency domain in order to study both DC and AC characteristics of solar cells. Here, we report on the extension of this frequency-dependent FEM model to the thermal domain, allowing us to calculate amplitude and phase images of solar cells that are voltagemodulated in the dark. We measured and modelled a screen-printed carbon-based hole-transporter-free perovskite solar cell with a defect, appearing as a hotspot in temperature measurements. In contrast to the traditional DLIT method using a large voltage modulation, we introduce a small-signal DLIT (SS-DLIT) imaging method which our model is capable to reproduce. Fitting thermal AC simulations to measured data, allowed to quantify the defect and examine its behaviour and origin.

8th World Conference on Photovoltaic Energy Conversion; 384-387, The carrier lifetime in unintentionally doped InGaP was significantly deteriorated with an increase in growth (surface) temperature from 560 to 590 °C. With a temperature higher than 600 °C, the growth of InGaP was failed with extremely rough surface morphology. Meanwhile, a larger amount of H2 carrier gas led to a faster TBP flow velocity and an improvement of InGaP surface roughness. These results suggested that, due to fast TBP decomposition processes, the depletion of TBP and insufficient P partial pressure for surface chemical reactions were major problematic issues for the growth of P-related materials in a large planetary MOVPE reactor. The quality of p-type InGaP grown in this reactor with TBP was not as good as that of n-type InGaP indicated by Hall mobility. In this work, InGaP rear homo junction (RJ) and rear hetero junction (RHJ) solar cells utilizing of thick n-InGaP layers exhibited much better photo-carrier collection and performance than the traditional n-on-p solar cell comprising of a thick pInGaP base layer. Moreover, the quality of InGaP was enhanced by the mis-orientation of GaAs (001) toward (111)A, while InGaP grown on GaAs (001) with a mis-cut toward (111)B showed worse results in term of carrier lifetime and solar cell performance.

8th World Conference on Photovoltaic Energy Conversion; 342-345, Thermal admittance spectroscopy (TAS) is often used to analyze trap states in CdTe thin-film photovoltaics. Specifically, the apparent energy level and the concentration of defects can be calculated using this method. In this work, we present TAS measurements on CdSeTe photovoltaic devices with varying Se concentrations and power conversion efficiencies from 12 % to 20 %. The results show two main trap signatures. The defects concentrations are evaluated using the emission parameter instead of the typically used capture cross-section. After correcting the emission parameter by the kinetic compensation effect, plots of PV performance versus the emission parameter of trap signature 1 show a good correlation, indicating that the emission parameter is suitable for determining concentration differences between the various samples.

8th World Conference on Photovoltaic Energy Conversion; 412-414, Luminescent solar concentrator (LSC) is a device with waveguide (or set of the waveguides) to transport sunlight to a photovoltaic cell attachment, where electricity is generated. We offer a new LSC design with the spectrum splitting on lateral plates. Such design substantially decreases the reflection losses, even though the escape cone losses increase due to absence of sequential utilization of descending photons. Ultimately, the lateral LSC can be substantially more efficient compared to the stacked LSC system. The efficiency of the lateral LSC design is determined by the dispersion system. In this research, we analyse four cases, namely: (i) Ideal solar spectrum separation without losses, considered as the limiting case. (ii) Dispersive prism system with the modeled efficiency above 80%. (iii) The set of dispersive mirrors. The experimental efficiency for every mirror can exceed 90%, but the losses are accumulated as for the stack of the LSC plates. (iv) Diffraction gratings. They are highly efficient for polarized light, but not for the unpolarized solar spectrum in the wide wavelength range. As we established, the dispersive prism and mirrors systems demonstrate the photon transport efficiency exceeding 57% for high-refractive index matrices. Photoconversion efficiency was assessed based on silicon solar cells (SCs).

8th World Conference on Photovoltaic Energy Conversion; 291-295, The Solar Cell Laboratory from the Instituto Tecnológico y de Energías Renovables (ITER), with the support of the La Laguna University (ULL), has been working on the development of low temperature encapsulation methods, suitable to protect Perovskite Solar Cells (PSCs). This document summarizes the work carried out to evaluate the performance of perovskite solar cells, based on MAPbI3 absorbers, which were encapsulated at low temperature and then the International Summit on Organic photovoltaic Stability (ISOS-T) protocols were applied. Three types of polymer materials were studied, those composed of Ethyl Vinyl Acetate (EVA), those composed of Poly(methyl methacrylate) (PMMA), and those composed of Polyvinylidene fluoride (PVDF) combined with EVA. The degradation of the samples was characterized by imaging microscope, optical ellipsometry and the electrical performance was simulated by the SCAPS-1D software. The results indicate EVA encapsulated samples remained stable after the 200 thermal cycles, keeping the samples a 15.06% PCE compared to the 15.96% PCE of the pristine ones, with a reduction of 5% of total efficiency, meanwhile the PMMA and EVA-PVDF samples lost 59% and 35% PCE respectively.

8th World Conference on Photovoltaic Energy Conversion; 328-330, At the present, attention of many researchers is focused on Sb2Se3, Sb2S3 and Sb2(Sx, Se1-x)3 chalcogenide compounds. This is due to the physical properties of these materials, such as p-type conductivity, band gap Eg = 1.1÷1.8 eV, high absorption coefficient 105cm-1 (for visible solar radiation), low melting point (823K and 885K for Sb2Se3 and for Sb2S3 respectively) and high partial pressure, which make these materials suitable for use as an absorbing layer in high efficiency thin film solar cells. In this work, we presented the effect of the Sb/Se ratio on the structural, morphological, and electrical properties of SbxSey films. SbxSey films were fabricated by chemical molecular beam deposition (CMBD) method from Sb and Se precursors at a substrate temperature of 500 at atmospheric pressure hydrogen flow. The scanning electron microscope and X-ray diffraction analysis show that all films have a crystallite size of 2÷3 μm and an orthorhombic crystal structure. The electrical conductivity of the films varies in the range of ~10-5÷ 102(Ohm • cm)-1 depending on Sb/Se ratio which was measured by van der Pauw method.

8th World Conference on Photovoltaic Energy Conversion; 457-461, This study aims to validate theoretical modelling of Plasmonic Luminescent Solar Concentrators(PLSC) software so that it can be used to optimize the PLSC fabrication process. The model will also be used to optimize the overall PLSC output in terms of solar power conversion, optical efficiency, dye concentration and device configuration. The two-stage process involves initially validating the LSC simulations by matching the modelling results with experimentally observed outputs, before moving onto subsequent PLSC model validation which requires further additional inputs, the metal nanoparticle extinction spectra, and the photon density enhancement factor (PDEF). The metal nanoparticle extinction spectra were measured experimentally and as the PDEF was the final remaining variable, it was taken from the literature and altered until it fit the particles being used in this study. The results of these simulations were then compared with the indoor and outdoor experimental characterizations and after noting that the trends and key data points correlated between the two methods of testing, the model was deemed to be validated.

8th World Conference on Photovoltaic Energy Conversion; 448-453, This paper presents a method to increase the dynamic range of the EL signal for diagnostics of defective areas in PV modules. It applies a computational method for reconstructing a high dynamic range radiance map from a stack of standard dynamic range images at multiple exposure times designed by Debevec and Malik for visible light cameras (RGB). Increasing the precision of the EL signal has two interests: more quantitative information is then available for automatic analysis, and better visual quality is available for visual inspection in case of a small amplitude EL signal, such as acquired in an outdoor daylight setup using lock-in EL. Both are demonstrated via two experiments during which a PV module is electrically biased and imaged at 8 different exposure times with an InGaAs camera: one indoor and one outdoor in daylight. The exposure times are combined to reconstruct an EL image of higher precision. To measure the increased precision, the number of unique pixel values is used: it increases by a factor larger than 2.5 for the indoor case and a factor higher than 100 in the outdoor case. In the outdoor case the improvement towards visual inspection is also clearly apparent.

8th World Conference on Photovoltaic Energy Conversion; 252-254, The industrial and economical transition of the perovskite (PVSK) photovoltaic (PV) technology is feasible by scaling-up effective PVSK recipe and post-treatment from small area cells ( 1 cm2) to sub-modules (≥ 200 cm2). In this work, we reported on the ambient air fabrication of a low temperature planar n-i-p PVSK submodule (total area 320 cm2, aperture area 201 cm2, 93% GFF) exploiting the defect passivation strategy, the PVSK composition and a hybrid blade/slot-die coating technique assisted by air and green antisolvent quenching method. Finally, the sub-module record efficiency is 16.13% with 7% and 0% losses with respect to small area cell and minimodule, respectively. Further details, characterizations, life cycle assessment (LCA) and stability test are in the full paper submitted to Progress in Photovoltaics.

8th World Conference on Photovoltaic Energy Conversion; 423-427, We report on the Scanning Tunneling Spectroscopy (STS) study of quantum dot sized SiGe alloy nanocrystals (NCs) to explore its bandgap energies. These alloy NCs have been prepared in a multichamber very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) reactor using a capacitively-coupled plasma technique. The STS study yielded a density of states (DOS) spectrum of NCs in which the conduction band (CB) and valance band (VB) edges were located, in addition, even midgap defect states in the forbidden region in some of the NC samples. The measured bandgap of SiGe alloy NCs in different samples reveals Ge content dependence. Though there was no dopant introduced intentionally during the growth, a shallow p-type nature of alloy NCs has been observed in all the samples even which may be attributed to charged grain boundary defects in high Ge content alloy NCs. The high bandgap value of NCs compared to bulk alloy indicates quantum confinement in the SiGe alloy NCs.

8th World Conference on Photovoltaic Energy Conversion; 373-377, This study was aimed at determining a suitable strain-balanced quantum structure to further improve the energy conversion efficiency of conventional Ge-based lattice-matched triple-junction solar cells. We investigated the voltage losses in several types of quantum-structure solar cells using the detailed balance theory and optoelectronic reciprocity relation. Based on the voltage loss analysis, we found that the combination of thick InGaAs quantum well layers and thin GaAsP layers was suitable for high-performance quantum-structured solar cells. To maintain the strain-balance condition for a quantum structure with thick InGaAs, we proposed the use of ultrahigh phosphorous composition GaAsP quantum barrier layers. The results of this study are significant for the design of future quantum-structure solar cells.

8th World Conference on Photovoltaic Energy Conversion; 358-361, The lattice mismatch is a significant issue for monolithic III-V/Si tandem solar cells due to the creation of islanding and misfit dislocations at the interface. Si1-xGex buffer layers have demonstrated promising results in mitigating the lattice-mismatch between III-V and Si materials. However, dangling bonds and dislocations can still exist among the Si1-xGex buffer layers, causing significant recombination losses. Herein, we apply an advanced hydrogenation process on Si1-xGex cells grown on Si with Si1-xGex graded buffer layers in between, aiming to reduce the buffer layer and base region defects, hence improving the cell’s performance. SiNx through PECVD has been applied as both a hydrogen source and an anti-reflection coating on SiGe/Si cells with four different Ge concentrations (i.e., 78%, 82%, 85% and 88%). After accumulated laser treatment of 30 seconds, Voc and efficiency of SiGe cells (78%, 82% and 85% Ge) have been improved by 2-4%REL (equivalent to 6-12 mV) and 5-17%REL, respectively. These results demonstrate the effectiveness of hydrogenation passivation on Si1-xGex buffer layers and SiGe base defects, also indicating opportunities for broad applications of the advanced hydrogenation technique on other tandem structures.

8th World Conference on Photovoltaic Energy Conversion; 222-226, Laterally inhomogeneous cell parameters in large scale perovskite/silicon (PSC/Si) tandem solar cells may significantly influence the device performance. The lateral quality of the absorber can be analysed with electroluminescence (EL), photoluminescence (PL) and thermographic methods. In addition to a global impact on cell performance, such lateral effects are often not considered in EQE and I-V-characterization of tandem devices, yet may lead to erroneous measurement results. Therefore, we see the necessity to employ large-area 3D PSC/Si-tandem simulations to understand the impact of lateral inhomogeneities, and the interaction with non-ideal measurement conditions such as small-area or non-uniform illumination of the solar cell. We use a tandem addon of the 3D simulation software Quokka3 for our full-cell 3D tandem simulations which treats the perovskite top cell skin, and optionally also the Si bottom cell, with an “equivalent-circuit” model instead of solving the drift-diffusion model. We present simulations and experiments to quantify the impact of inhomogeneous cell properties such as low localized shunt resistances or non-uniformities of the cell absorber, in interaction with the illumination and biasing conditions during the EQE measurement. It is specifically interesting to gain insight into lateral effects by simulation, as the experimental investigation of such detailed effects in often metastable PSC/Si tandem cells is highly challenging.

8th World Conference on Photovoltaic Energy Conversion; 402-405, Solar cells using stacks of a polycrystalline silicon layer and an ultra-thin silicon oxide layer have commanded considerable attention due to their high conversion efficiency. However, thinning the silicon oxide film to transport carriers leads to a decrease in passivation performance. Therefore, we have developed the NAnocrystalline Transport Path in Ultra-thin dielectrics for Reinforced passivation (NATURE) contact that combines both thickness and conductivity. Hydrogen plasma treatment (HPT) is an effective method to improve passivation performance. We previously reported that the implied open circuit voltage (i-VOC) was significantly improved after HPT at 500 °C. For further improvement, we here investigate the impact of the HPT duration and the H2 pressure on the i-VOC values and on the hydrogen depth distribution. The i-VOC was measured by the quasi-steady state photo-conductance method and the hydrogen depth distribution was characterized by resonant nuclear reaction analysis (RNRA). This revealed that hydrogen atoms are sufficiently incorporated into the NATURE contact for HPT duration of 15 min at a H2 pressure of 0.5 Torr, yielding the highest i-VOC of 724 mV.

8th World Conference on Photovoltaic Energy Conversion; 320-323, Many reports attribute the origin of S-type characteristics in the thin film solar cells to interface recombination and energy level mismatch between materials. However, along with interface degradation and non-ideal energy levels of materials, ion migration is an unavoidable phenomenon in perovskite solar cells whose impact on the S-type characteristics is not well established. Here, we use a double diode approach to study the formation of S-type characteristics, in which the first diode characteristics is due to the energy level offset, interface recombination and ion distribution. The second one is the conventional diode which represents the drift and diffusion current in the device. Insights from the study also provide theoretical explanation on different shapes of S kink seen in the J-V characteristics using double diode approach.

8th World Conference on Photovoltaic Energy Conversion; 302-305, With their exceptional optoelectronic properties, compatibility with low-cost and large-scale fabrication methods, organic-inorganic hybrid metal halide perovskites are poised to revolutionize the next generation of photovoltaics. The leap forward in the power conversion efficiency (PCE) enabled by lead halide perovskites is unprecedented, with PCEs emerging from 3.8% in its first study to a current certified value of 25.5% in single-junction and 29.52% in perovskite-silicon tandem devices [1-3]. The main challenge for the successful commercialization of perovskite solar cells is to achieve high stability at the module level. The commercially available solar modules undergo a series of characterization procedures that analyze their properties and ensure their quality. However, these procedures and protocols cannot unambiguously be applied to perovskite solar modules (PSM). To this end, more advanced characterization methods are needed to understand the degradation mechanisms in the PSM. In this context, optical and electrical measurement methods are effectively employed in quality control and development support and are essential characterization tools in industry and research.

8th World Conference on Photovoltaic Energy Conversion; 279-281, By maximizing the interaction of sunlight with the absorber, light trapping allows for more than one order of magnitude reduction in the solar cell thickness with minor impact on performance. This possibility has been experimentally demonstrated for mature technologies, such as Si and GaAs ultrathin solar cells, with very high shortcircuit currents (JSC). In this work, we optimize the optical properties of a 100 nm-thick GaAs solar cell using a periodic subwavelength diffraction grating and demonstrate an optically equivalent JSC of 27.2 mA/cm2. Along with the calculations of the optical properties and a detailed analysis of the losses, we present a step-by-step evolution of the light trapping design from a simple back mirror to an advanced design combining a semiconductor diffraction grating, a spacer layer and a flat mirror. Finally, we go one step further in the optimization using OptiPV, an in-house developed software. It combines optical simulations with electrical simulations using SCAPS, through the calculation of the carrier generation rate in stacks that include photonic nanostructuration, allowing to consider practical aspects of the device operation.

8th World Conference on Photovoltaic Energy Conversion; 438-443, Renewable energies have an increasing share in the energy supply. In order to ensure the security of this supply, the reliability of the systems is therefore increasingly important. In photovoltaic modules or in manufacturing defective solar cells due to broken busbars, cross-connectors or faulty solder joints must be detected quickly and reliably. This paper shows how the magnetic field imaging method can be used to detect defects in solar cells and modules without contact during operation. For the evaluation of the measurement data several neural networks were used, which were trained with the help of results from finite element simulations. Different training data sets were set up in the simulation model by varying the electrical conductivities of the different parts of the solar cell. There is an advantage of a combination of simulated and experimental training data, which is presented and discussed.

8th World Conference on Photovoltaic Energy Conversion; 316-319, Additive engineering in perovskite devices has been explored in the last few years towards enhancing photovoltaic performance and stability. Control of the morphology, grain boundary, grain size, charge recombination and density of defect states in the perovskite layer are important for the optimization of the perovskite-based devices. In this work, we study the stability testing of perovskite cells with and without 3-phosphonopropionic acid (H3pp) additives in the active perovskite layer at different loading conditions in an attempt to detect differences in their photocurrent and External Quantum Efficiency (EQE) spectrum due to the different loading conditions. Raman spectroscopy and spatially-resolved Electroluminescence (EL) techniques were applied before and after degradation of the samples to detect differences in their molecular composition and defect evolution respectively. Measurements revealed the higher stability of the perovskite with H3pp additives and the larger impact of loading conditions in those cells. EQE measurements established higher reduction of the EQE values in the control cells (cells without additives). Finally, spatially-resolved EL measurements indicated larger recombination losses in control cells while Raman measurements demonstrated changes in the Formamidinium (FA) cation composition in the control cells.

8th World Conference on Photovoltaic Energy Conversion; 399-401, In this work, ultrathin GaAs solar cells are presented with a rough backscattering structure based on lattice mismatched gallium phosphide, grown with MOCVD. This way, a simple and reproducible light-trapping scheme is introduced with low parasitic absorption and full compatibility with hydrofluoric acid-based epitaxial lift-off. Solar cells with two different GaP surface morphologies are demonstrated and shown to be compatible with epitaxial lift-off without any complications or performance loss. An increase in short-circuit current density of up to 9% is observed, a direct result of the increased photon absorption induced by the scattering of the rough GaP texture.

8th World Conference on Photovoltaic Energy Conversion; 227-229, Traditional silicon-based solar cells generally can only absorb the solar spectrum with wavelengths below 1.1 microns, and others cannot be absorbed but consumed in the form of heat. In this research, the metal/semiconductor junction is used to break through the limitation of silicon bandgap, and hot carrier effect is applied. The metal thin layer is used to absorb sunlight to generate hot carriers, quickly passing through the energy barrier to generate photocurrent, maximizing the use of solar energy. Compared with conventional silicon solar cells on the market, metal/silicon junction solar cells have better absorption and photovoltaic performance in the infrared regime, expanding the absorption range of silicon-based solar cells, and more effectively utilizing the entire solar spectrum.

8th World Conference on Photovoltaic Energy Conversion; 313-315, The aim of this work is the study of the degradation of two different PSCs. A PSC with undoped SnO2 ETL was compared to a PSC with ETL made of G-SnO2. Degradation was monitored by performing both impedance spectroscopy and dark I-V measurements. Experimental data were collected just immediately after fabrication and after one week. It was observed that the degradation of the solar cells affects both the AC behavior of the devices, modifying associated Nyquist plots, and the DC behavior, observable from dark current-voltage curves. From the Nyquist plots a quantitative analysis was performed by comparing the parameters of a proper equivalent circuit model. Results were coherent with those achieved with DC analysis, thus providing that the arising from these two techniques allows to gain a deeper knowledge of the degradation phenomena.

8th World Conference on Photovoltaic Energy Conversion; 428-430, Although silicon and perovskite solar cells have achieved efficiency of up to 26 % , their efficiency is still limited by several factors, such as the reduced efficiency in the ultraviolet region of the solar spectrum. One of the proposed mechanisms to overcome this problem is to use wavelength shifters. The objective of this work was to investigate optical and structural properties of thin films of common photoluminescent pigments used in several areas, such as coatings, graphic arts, cosmetics and adhesives. Thin films of the pigments and tin dioxide (SnO2) films with embedded pigments were prepared by spin coating. The films excited by ultraviolet laser present emission in the visible region, thus functioning as wavelength shifters, which can potentially be used to improve the absorption of ultraviolet light in solar cell.

8th World Conference on Photovoltaic Energy Conversion; 255-259, Regarding the interface between Si bottom cells with poly-Si on oxide (POLO) junctions as the uppermost layer and the lowest layer of a perovskite (Pk) top cell (i.e., the hole-selective layer HTL in pin configuration), many questions are still open, including the one which layers are actually required for low-resistive subcell interconnection. In this work, we compare recombination-layer (RL) and tunneling junction (TJ) - based subcell interconnection schemes, namely spiro-TTB/n+ poly-Si, spiro-TTB/p+ poly-Si/n+ poly-Si, and spiro-TTB/ITO/n+ poly-Si. The first is – to our knowledge for the first time – investigated experimentally. We prepare dedicated Pk/Si test structures, which are opaque co-evaporated MAPbI3 top cells on Si substrates with the uppermost layers of interest. DarkIV and frequency-dependent impedance measurements are applied. We reveal an upper limit for the contact resistance of 14 mΩcm2 for the p+ poly-Si / n poly-Si tunnel junction with Cox&Strack measurements. We observe a reduction of the current densities measured on our Pk/Si test structures upon biasing at more than 1 V, that stabilizes at a factor of ~1/300 for the spiro-TTB/ITO and of ~ 1/10 for both spiro-TTB/poly-Si interfaces as compared to the initial measurement. After stabilization, our IV measurements show that the spiro-TTB/n+ poly-Si recombination junction conducts comparable current densities as the spiro-TTB/p+ poly-Si interface. Within a framework of a three-element equivalent circuit for impedance measurements, the spiro-TTB/X interface affects the voltage dependent parallel resistance. The comparable current densities for the spiro-TTB/n+ poly-Si and the spiro-TTB/p+ poly-Si interface gives hope that n+-type poly-Si can indeed work as a recombination layer itself, although we did not succeed in a quantification of the specific resistance of the spiro-TTB/X interface. This indication has to be verified on full tandem cells.

8th World Conference on Photovoltaic Energy Conversion; 454-456, The most common equivalent electrical circuit of a real solar cell is probably the one-diode model. Throughout the years, numerous research have focused on the extraction of model parameters from measurements done in standard test conditions (STC) with the goal of replicating the current-voltage characteristics (I-V). The equation that describes the I-V characteristics is highly nonlinear, and also an implicit equation. There are many attempts to write an explicit equation, achieving only limited success. This study proposes an explicit Shockley equation for the five-parameter solar cell model. The form of the equation is new, consisting of the ideal Shockley equation and an additive term. The results confirm the feasibility of the proposed approach, indicating a promising way to a simpleexplicit five-parameter solar cell model.

8th World Conference on Photovoltaic Energy Conversion; 270-272, Multijunction (MJ) solar cells achieve very high efficiencies by effectively utilizing the solar spectrum. Previously, we constructed a GaAs//CuIn1-yGaySe2 (CIGSe) MJ solar cell using a unique mechanical stacking technology with Pd nanoparticle and silicone adhesive at the bonding interface (modified smart stack technology). The modified smart stack was developed to increase the bonding strength of the GaAs//CIGSe interface. The efficiency of 28.06% with a InGaP/AlGaAs//CIGSe three-junction solar cell was the best value among GaAs//CIGSe tandem solar cells as two-terminal. In this report, we fabricated a flexible InGaP/AlGaAs//Cu(In1-x,Gax)(Sy,Se1-y)2 (CIGSSe) threejunction solar cell using a flexible CIGSSe bottom cell. Appling the modified smart stack, the total efficiency with 24.3% for aperture area (26.7% for active area) was realized under the global standard AM1.5G spectrum. This is the first demonstration as a flexible GaAs//CIGSe-based MJ solar cell. The superior performance can be achieved by improving the reflection loss at the bonding interface. We predict that the efficiency could be boosted to 35% by minimizing the thickness of transparent conducting oxide layer and the surface roughness of CIGSSe cell. The results demonstrate the potential of GaAs//CIGSe-based MJ solar cell as next-generation solar cells for application such as vehicle-integrated photovoltaics.

8th World Conference on Photovoltaic Energy Conversion; 415-418, Since the photoconversion efficiency of the silicon-based solar cells (SCs) is approaching their theoretical fundamental limit close to 29%, further improvement of their performance requires theoretical modeling and/or numerical simulation to optimize the SCs parameters and their design. For several types of high-performance silicon-based SCs with both flat and textured top surfaces, we (i) analyzed experimentally key characteristics, namely external quantum efficiency (EQE), short-circuit current density JL(d), open-circuit voltage VOC, I-V curves and the efficiency ; (ii) modeled these characteristics by a semi-analytical approach, developed by the authors, and (iii) numerically simulated using Quokka, SunSolve and other dedicated software. Analyzing and comparing the combined experimental, modelled and simulated results provide valuable information to further improve the design and enhance the SCs performance. The experimental EQE() curves for high-efficiency silicon planar and textured SCs have been analyzed in terms of the base thickness dependent short-circuit current density JL, calculated using the empirical formula for EQE(), and the same parameters were simulated using Quokka 3. The theoretical and modeling results, dependent on the SCs type and structure, recombination parameters, radiation intensity, etc., agree well with the experiment for the considered IBC type flat and textured SCs.

8th World Conference on Photovoltaic Energy Conversion; 435-437, This work presents a comprehensive opto-electrical simulation model in Sentaurus TCAD for perovskite-silicon tandem devices which incorporates sophisticated physical models that allow for an in-depth study of efficient charge carrier extraction in tandem devices.

8th World Conference on Photovoltaic Energy Conversion; 230-233, Vehicle-integrated photovoltaics (VIPV) are gaining attention to realize a decarbonized society in the future, and the specifications for solar cells used in VIPV are predicated on a low cost, high efficiency, and the ability to be applied to curved surfaces. One way to meet these requirements is to make the silicon substrate thinner. However, thinner substrates result in lower near-infrared light absorption and lower efficiency. To increase light absorption, light trapping structures (LTSs) can be implemented. However, conventional alkali etched pyramid textures are not specialized for near-infrared light and are insufficient to improve near-infrared light absorption. Therefore, in this study, as an alternative to alkaline etching, we employed a nanoimprinting method that can easily fabricate submicron-sized LTSs on solar cells over a large area. In addition, as a master mold fabrication method, a method using silica particles as a mask was adopted. As a result, control of the LTSs structure was confirmed by silica particles. The sample with LTSs achieved a reduction of reflectivity in the near-infrared region (1000~1200 nm) and a theoretical maximum gain of Jsc of 1.65 mA/cm2.

8th World Conference on Photovoltaic Energy Conversion; 419-422, We have investigated the effect of light trapping on the photoabsorption in quantum dot (QD) solar cells. Numerical simulations show that optimizing the positions of quantum dot layers can lead to an absorption enhancement using Fabry-Perot (FP) resonance and guided diffracted modes. Further, we experimentally demonstrate that positioning the InAs/GaAs quantum dot layers at the intensity peaks of FP resonance results in an increase of EQE and hence photocurrent. This effect can be used to improve the performance of QD solar cells and also photodetectors.

8th World Conference on Photovoltaic Energy Conversion; 406-408, In this work, we study the growth of Sb2Se3 deposited by thermal evaporation on different buffer layers for superstrate configuration thin film solar cells. A comparison between CdS which has been widely used as a buffer layer and CdSe is represented. Selenium vacancies in Sb2Se3 thin film act as recombination centers, and according to the literatures, applying an excessive amount of Se improve the application of solar cell. By using CdSe as a buffer layer, selenium could diffuse into the film and it is supposed to increase the efficiency. In our case both devices show the same efficiency of around 3.5% and higher Jsc for CdSe device. Also, morphology results indicate slightly higher crystal quality for CdSe/Sb2Se3 thin film and the solar cells perform almost the same degradation results.

8th World Conference on Photovoltaic Energy Conversion; 369-372, In this study, a temperature-graded growth layer (TGL) is newly introduced to achieve continuous growth between AlGaAs and InGaP grew at 700ºC and 560ºC, respectively. It is observed that the deterioration of Voc is successfully mitigated after this grading layer is applied. Absolute electroluminescence and atomic force microscopy measurements are further performed to confirm an enhanced ERE and improved interface topography, indicating that the TGL can effectively suppress oxygen incorporation at AlGaAs/InGaP heterojunction, thereby improving the smoothness of the epitaxial layer, which in turn prohibits nonradiative recombination. In all, the TGL is verified to enhance the quality of AlGaAs/InGaP heterojunction solar cells and may serve as a general routine for AlGaAs-based heterogeneous growth with metal-organic vapor phase epitaxy (MOVPE).

8th World Conference on Photovoltaic Energy Conversion; 388-391, This paper describes the results achieved during the qualification campaign conducted on Solar Cell Assemblies CTJ30-80-SCA manufactured by CESI using the qualified CTJ30-80 thin (80 m) bare solar cells. The results of a set of specific engineering tests grouped under the denomination of “Subgroup M” aimed at verifying the flexibility and the reliability of thin (80 m) solar cells / solar cell assemblies mounted on curved surfaces or on flexible supports are also summarized. The use of solar cell assemblies based on thin solar cells and flexible coverglasses in the fabrication of non-planar solar arrays or flexible structures requires the assessment of the bending capabilities of the solar cell assemblies. The aim of this activity was the identification of procedures and methods to test the cell behavior in bending configuration in BOL and EOL conditions.

8th World Conference on Photovoltaic Energy Conversion; 265-269, In accordance with “Net zero emissions” goal, annual photovoltaic (PV) production must be expanded to terawatts (TW) scale around 2030. This goal not only accelerates the requirement of improvement on efficiencies of solar cells, but also intensifies the consumption of scarce materials contained, especially in the high efficiency Si-based tandem solar cells. This abstract provides a sustainability analysis of various potential silicon-based tandem solar cell designs in heading towards terawatt scales of annual PV production by 2030 on the path towards net-zero emissions by 2050. It investigates the current and target consumption values of critical elements for future silicon-based tandem devices in the absorbing materials (eg. III-V, CIGS, CdTe and perovskite), and bottom cell (PERC, TOPCon and SHJ) candidates and requirement for metal electrodes, as well as lateral conductors/buffer layers typically based on indiumtin-oxide (ITO). We show that III-V, CIGS and CdTe top cells will not support TW scales of manufacturing, with perovskites provide the most sustainable top cell, if it is indium-free. For the bottom cell, PERC could allow significantly lower silver consumption than TOPCon and SHJ cells.

8th World Conference on Photovoltaic Energy Conversion; 276-278, We have studied Ag incorporated Sb2(SxSe1-x)3 bi-layer devices by modeling and simulation to optimize the absorber layer. Four different device structures are extensively investigated to optimize the device configuration. Firstly, as a frame of reference, simple single-layer devices are studied with the absorber film of each AgSb(SxSe1-x)3 and Sb2(SxSe1-x)3 as the Sulfur composition increases. Following the study of reference devices, the impact of Sulfur composition on bi-layer devices has been modeled and simulated with two different absorber configurations such as Sb2(SxSe1-x)3/AgSb(SxSe1-x)3 and AgSb(SxSe1-x)3/ Sb2(SxSe1-x)3. Compared with any single-layer devices, the absorber configuration of AgSb(SxSe1-x)3/ Sb2(SxSe1-x)3 bi-layers shows best performance at the Sulfur composition, x = 0.4. This is ascribed to the reduced effective Schottky barrier by 126 mV at the back contact, improving the roll-over effect by 4.3 times at 1 V. The resulting efficiency is 18.6 %, Voc, is 778.9 mV, Jsc is 37.2 mA/cm2, and FF is 64.0 %. Once the bi-devices with the highest efficiency and the optimal Sulfur composition are identified, a set of different device parameters have been studied to optimize these bi-layer devices further. The best efficiency is 21.4 % with Voc (822 mV), Jsc (38.1 mA/cm2), and FF (68.4 %) based on this study.

8th World Conference on Photovoltaic Energy Conversion; 331-334, The interface-associated organic photovoltaics (OPVs) devices consider a vital issue that affects their overall performance. Accordingly, in the present work, we demonstrated an efficient interfacial modification through using conjugated poly electrolytes (CPE) to modulate the barrier for charge injection into the semiconducting layers and in turn improve the device performance Herein, we report an aqueous conjugated poly electrolyte of PCPDTPhSO3-Na as a buffer interlayer to modify the interface between the hole transporting layer (HTL) of MoO3 and the active blend of PM6:Y7 in an inverted device architecture of ITO/ZnO/PM6:Y7/HTL/Ag. This bi-stack modulates the interfacial traps through diminishing the accumulated charges and in turn, enhances the transfer and the collection of the generated current. Accordingly, the PCPDTPhSO3-Na/MoO3 based devices exhibited higher short circuit current density than the MoO3 based ones by 8 %, and the fill factor was further enhanced by 5 %, consequently, the power conversion efficiency improved by 14 %.

8th World Conference on Photovoltaic Energy Conversion; 462-469, In the last 18 years PV solar power has increased from 0 to 500 GWp approximately as indicated by International Energy Agency Photovoltaic Power Systems Program IEA PVPS [13]. However, an issue that has been left aside is the maintenance of the constituent elements of a solar PV plant, this mainly because the elements are still under warranty. In particular, one of the fundamental players in a solar PV plant is the Photo Voltaic Solar Module PVSM, which usually has a guarantee of around 20 years. However, it has been proven that in practice a large number of modules have presented unexpected failures, e.g., power degradation faster than what the manufacturer considered when defining the warranty. Considering an average annual degradation of 1%, it would be expected that within the first 10 years, the PV modules of a PV plant present a 10% degradation in their performance. In this work it is carried out a characterization of the electrical behavior of a bifacial photovoltaic solar module obtained through static and transient analyses operating under no-fault and fault conditions at controlled conditions using the Flasher IV A+A+A+ Solar Simulator of Eternalsun. Later, the response of photovoltaic solar modules, for their healthy and faulty operation, were studied. As a result, it is obtained a characterization of the electrical behavior of bifacial photovoltaic solar module under nofault and fault conditions at controlled level.

8th World Conference on Photovoltaic Energy Conversion; 287-290, Perovskite solar cells (PSCs) have made tremendous progress in the past years with an efficiency of over 25% in lab-scale devices. Scalability of the perovskite technology is one of the major challenges that restrict perovskites from entering the market. In this research, we performed a systematic experimentation study to demonstrate the scalability and stability of our perovskite-based Solar InkTM and demonstrated its compatibility with different coating processes. The goal is to address the industry need of improving the performance of the perovskite solar cells by having a stable perovskite ink compatible with air-processing and ambient atmosphere, and reduce the fabrication cost by eliminating the requirement of a controlled environment. The aim of this work is to demonstrate the stability and scalability of our novel perovskite ink (Solar InkTM) with high efficiency and stability, and its compatibility with a variety of scalable manufacturing processes.

8th World Conference on Photovoltaic Energy Conversion; 409-411, The aim of this work is the study of beneficial effects of HNO3 doping for G/Si SJSCs by means of capacitance versus voltage (C-V) curves and impedance spectroscopy characterizations. Capacitance curves in forward bias allowed to characterize defects distribution at graphene/silicon interface, proving induced defect passivation of molecular doping. Impedance spectra both at reverse and forward bias enforced achieved results. Degradation after storing the solar cell in air was also monitored using the same techniques. AC analyses performed were confirmed by dark current-voltage (I-V) curves collected before doping, after doping and 2 weeks after doping storing cell in air.

8th World Conference on Photovoltaic Energy Conversion; 470-473, Building integrated photovoltaics (PV) is among the major PV technologies being pursued to align with the energy efficiency buildings and net-zero emission policies. Semi-transparent solar cells could be key components to achieve these targets and efforts are underway to develop novel PV absorbers and devices with the priority of materials’ abundance, cost and stability. Sb2S3 thin films are promising PV absorbers owing to their superior optoelectronic properties, stability and availability of raw materials. However, the conventional expensive hole conductors like P3HT and Spiro-OMeTAD coupled with their post-processing needs and stability issues could be obstacles for Sb2S3 solar cells. In this study, cost-effective and transparent fluorene and thiophene-based hole transport materials (HTM) are explored in Sb2S3 solar cells. HTMs are spin coated to fabricate solar cells in the superstrate configuration (Glass/FTO/TiO2/Sb2S3/HTM/Au) wherein TiO2 and Sb2S3 are ultrasonic spray deposited. Solar cells with new HTMs have yielded similar power conversion efficiencies (3.8-3.9 %) compared to P3HT-based cells (3.7%) while exhibiting 20-25 % enhanced average visible transmittance (400-800 nm) in the device stack without the metal contact. Optical properties and band energetics of individual layers demonstrate that the new cost-effective HTMs exhibit favourable band off-set for application in semi-transparent Sb2S3 solar cells.

8th World Conference on Photovoltaic Energy Conversion; 296-301, We report the use of slot-die coating as an up-scalable technique to convert a co-evaporated CsBr/PbI2 precursor layer into a triple-cation mixed halide perovskite. We optimize this two-step deposition process by varying the coating parameters such as the evaporation rates in the first step and the solution concentration and dispense rates in the second step. We observe that the co-evaporation of CsBr and PbI2 at 0.1 A s-1 and 1.0 A s-1, respectively, results in a porous layer which is desired for the conversion by slot-die coating. In the second step, with an optimization of solution concentration (40.7 mg/mL) and solution dispense rate (3.3 µL s-1), uniform perovskite film with large grain size on the 5 x 5 cm² substrates is achieved. The homogeneity, composition and stoichiometry of the converted perovskite film were studied using X-ray Photoelectron Spectroscopy (XPS), from surface to bulk, using in depth profiling by sequential Ar+ sputtering. The perovskite layer has been implemented into a single-junction device, yielding a champion efficiency of 13.5% power conversion efficiency with hysteresis (average 10 - 11%), which is the first cell efficiency obtained using this hybrid deposition method based on the dual-source CsBr/PbI2 thermal evaporation and slot-die coating.

8th World Conference on Photovoltaic Energy Conversion; 234-236, The present work proposes another way to obtain solar cells based on PZN-PT ferroelectric oxides with very high efficiency beyond that of halogenated perovskites and requiring only ferroelectric nanoparticles dispersed in biopolymer matrix thus allowing the reduction of their environmental impact. In our recent studies, we successfully fabricate thin films on ITO substrate by dispersing these nanoparticles in a biopolymer. We demonstrated that they conserve the ferroelectric properties of the PZN-PT bulk crystal. The idea to use these ferroelectric materials (PZN-PT) came from the fact that the ferroelectric nature of these layers could facilitate electric charges accumulation on the interfaces of the solar cell. Thus, it would increase the open circuit voltage Voc which could reach more than 10 V. This would directly impact the efficiency which is proportional to Voc, thus hoping to obtain solar efficiency never equaled by the halide perovskites which are less stable and less resistant in aggressive environments. The cell produced gave an exceptional record efficiency with an open circuit voltage (Voc) of 3.50 V, a short-circuit current density (Jsc) of 0.118 mA/cm2 and an FF of 0.72 measured in the positive polarization direction under 3825 lux (5.6 W/m2) lightning.

8th World Conference on Photovoltaic Energy Conversion; 324-327, This work focuses on the development and evaluation of a system for the deposition of ZnO thin films with improved thickness homogeneity and suitable optoelectrical properties to be used as TCO layer in solar cells, using the Plasma Assisted Reactive Evaporation (PARE) method. This development made it possible to significantly improve the inhomogeneity of the thickness of the ZnO films that were deposited using a previous version of the PARE system developed by our Group. Through modeling and theoretical simulation of the processes that take place during the deposition of ZnO thin films by the PARE method, information was obtained that allowed the implementation of a reactor with a novel design that allowed the growth of large-area ZnO films with good homogeneity in thickness. By optimizing the preparation parameters, it was possible to deposit large area ZnO thin films with similar values of resistivity and transmittance than those obtained with small area ZnO films deposited using the previous version of the reactor. ZnO films with resistivities varying between 9.5*10-4 and 2*104 Ωcm and transmittances greater than 85% (in the visible region) were achieved.

8th World Conference on Photovoltaic Energy Conversion; 219-221, In this work, we demonstrate a novel semi-transparent solar cell based on ultrathin hydrogenated amorphous Si/Ge multiple quantum wells (MQW). This concept allows extra degree of freedom for both optical design and bandgap engineering compared to single QW structures. Mainly, the multiplication of the QWs number in a periodic configuration, taking advantage of effective synergy between electronic and photonic confinements, leads to an improvement of photocurrent, while preserving high voltage and fill factor and ensuring significant transparency. The MQW new concept yields a boost in power conversion efficiency up to 3.4% and a considerable average visible transmission of about 33%. The achieved performance points out the promising potential of the proposed semitransparent ultrathin QW solar cell for glass façades and solar windows applications.

8th World Conference on Photovoltaic Energy Conversion; 431-434, Photovoltaic (PV) devices based on metal halide perovskite technology are typically more sensitive to environmental conditions, such as moisture and oxygen, than conventional inorganic PV materials like silicon. This means scalability and commercialization of perovskite PV technology are reliant upon highly effective and reliable encapsulation schemes. Evaluation of edge seal materials and encapsulation effectiveness can be challenging, especially if contactless schemes for characterisation are required. In this work, a contactless technique to evaluate encapsulation methods for perovskite devices is presented, based on photoluminescence (PL) imaging. Perovskite devices exhibit a strong PL emission signal when illuminated, while there are dramatic changes in the local PL emission when the devices degrade due to interactions with moisture or oxygen. Such changes in PL signal present an effective way to monitor the effectiveness of encapsulation schemes for perovskite devices. Triple-mesoscopic carbon perovskite mini modules were encapsulated with different schemes and subjected to damp heat aging tests at 85 °C/85 % relative humidity in the dark. PL imaging was used at different times during ageing to monitor the spatial PL emission of samples. In addition, encapsulated devices were placed outdoors and were monitored by PL imaging at frequent intervals in order to compare outdoor exposure with accelerated tests. It has been demonstrated that encapsulation failure can be identified at different times during ageing, with an observed decrease in measured short circuit current of the aged device. Novel encapsulation schemes can be tested using this methodology and compared with more common encapsulation methods.

8th World Conference on Photovoltaic Energy Conversion; 339-341, In our laboratory, Cu2ZnSn(S,Se)4 (CZTSSe) films are prepared by selenization of spin coated CZTS precursors. In this study, different temperatures are tested for the selenization process and their effects on the device are investigated. The influence of the selenization temperature on the Se incorporation and structural properties of the absorber have been analyzed by X-ray diffraction, Raman spectroscopy and scanning electron microscopy methods. Current-voltage analysis reveals a fill factor reduction with increasing temperature, concurrently with an improvement in short circuit current and efficiency. SLG/Mo/CZTSSe/CdS/iZnO/ITO/Au cells fabricated with selenization process at 550 °C reach an efficiency of 6.3 %.

8th World Conference on Photovoltaic Energy Conversion; 306-312, In this work an improved carbon-based composite and a simplified architecture has been developed to produce and deposit a back contact to fabricate HTM-free Perovskite Solar Cells in ambient conditions. A batch of cells were produced that had efficiencies stabilized at about 1%, with a record value of 1.646%. Estimations of the devices’ serial and shunt resistances were also obtained, resulting on 2kΩ and 200Ω respectively, which indicates that, on the one hand, they are still too inefficient at allowing the flow of the photo-generated electrons and, on the other, that alternative recombination pathways yet exist, which further hamper their efficiencies. Also, the observed phenomena of IV curve hysteresis (between the forward and reverse measurements), together with a yellowing of the perovskite layers after completing a set of tests under continuous illumination, suggest that substantial ionic shift happens in the crystal lattice, that also contributed to its degradation. In order to compensate these effects, different strategies were proposed, which will be tested in future iterations.

8th World Conference on Photovoltaic Energy Conversion; 237-240, Lower performances are usually recorded for perovskite and silicon/perovskite tandem solar cells that use tin oxide (SnO2) grown by Atomic Layer Deposition as an electron selective layer instead of solution-processed SnO2. This work attempts to determine possible causes for such limitations. A comparative study on chemical, electrical, optical and topographical properties of ALD-grown SnO2 and solution-processed SnO2 thin films and on their integration in perovskite-based solar cells is presented. This study points out the SnO2/perovskite interface as the main performance-limiting element. Specifically, a larger workfunction for ALD-grown SnO2 may create a potential barrier for electron extraction at PK interface.

8th World Conference on Photovoltaic Energy Conversion; 392-395, The rear-hetero structure InGaAsP (1.04 eV) single junction (RHJ) solar cells are fabricated and investigated in this study. The rear-hetero structure in III-V semiconductor based photovoltaic cell is focused their substantial enhancement of open-circuit voltages (Voc). Because there still a few examples of low bandgap material have been developed for an improved mechanical stacked multijunction solar cells, it is important to qualify the material of lattice-match InGaAs and InGaAsP grown on InP substrate. In addition to the standard light I-V and quantum efficiency (QE) measurement, an absolute measurement of electroluminescence (EL) under the current injection equivalent to the photo-carrier generation with AM1.5G illumination is demonstrated. Owing to the reciprocal relationship between the light absorption and emission in the photovoltaic devices, the device performance is qualified as a luminescent efficiency. Adjusting the lattice matching condition, the obtained RHJ InGaAsP solar cell reached to 0.653V of Voc and the corresponding external radiative efficiency (ERE, ext) is measured as ext ~3.0%.