Fill Factor Of Solar Cells Research Articles

Reducing damage of sputtering and improving conductivity of transparent electrodes for efficient semi-transparent perovskite solar cells

Sputtered indium tin oxide (ITO) is widely used as an electrode in semi-transparent and tandem perovskite solar cells. However, damage from sputtering to under layers and the limited conductivity of ITO are still the two main obstacles that hinder further performance improvement of the devices. In this work, the effects and mechanism of sputtering damage and poor conductivity of ITO are investigated based on a traditional perovskite solar cell with bathocuproine (BCP) buffer layer. In order to suppress the sputtering damage, tin oxide (SnO2) is deposited on C60 to replace the BCP buffer layer. However, it is found that the deposition of SnO2 on the non-reactive C60 by atomic layer deposition will result in island growth of SnO2 film, which is the key reason for large dark current in solar cells. Fortunately, the phenomenon is inhibited by decorating C60 surface with WO3 thin film. In order to improve the conductivity of the transparent electrode, an ITO/Au/ITO multilayer architecture is designed. The fill factor (FF) and power conversion efficiency (PCE) of the semi-transparent solar cells (ST-PSCs) with the modified buffer layer and electrodes reached 76.4% and 17.62%, respectively, showing an improvement of FF and PCE when compared to the device with BCP buffer layer and ITO electrode. It is revealed that the optimization also increases the short circuit current of the solar cells. These results provide new strategies for damage reduction of sputtering and performance improvement of ST-PSCs.

Spontaneous decoration of ionic compounds at perovskite interfaces to achieve 23.38% efficiency with 85% fill factor in NiOX-based perovskite solar cells

Inorganic hole transport materials, particularly NiOX, have shown considerable promise in boosting the efficiency and stability of perovskite solar cells. However, a major barrier to commercialization of NiOX-based perovskite solar cells with positive-intrinsic-negative architectures is their direct contact with the absorbing layer, which can lead to losses of photovoltage and fill factor. Furthermore, highly positive under-coordinated Ni cations degrade the perovskite at the interface. Here, we address these issues with the use of an ionic compound (QAPyBF4) as an additive to passivate defects throughout the perovskite layer and improve carrier conduction and interactions with under-coordinated Ni cations. Specifically, the highly electronegative inorganic anion [BF4]− interacts with the NiOx/perovskite interface to passivate under-coordinated cations (Ni≥3+). Accordingly, the decorated cells achieved a power conversion efficiency of 23.38% and a fill factor of 85.5% without a complex surface treatment or NiOX doping.

Improvements and gaps in the empirical expressions for the fill factor of modern industrial solar cells

Improvements and gaps in the empirical expressions for the fill factor of modern industrial solar cells

Disentangling the effect of the hole-transporting layer, the bottom, and the top device on the fill factor in monolithic CIGSe-perovskite tandem solar cells by using spectroscopic and imaging tools

We present monolithic copper–indium–gallium–diselenide (Cu(In,Ga)Se2, CIGSe)-perovskite tandem solar cells with air- or N2-transferred NiO x :Cu with or without self-assembled monolayer (SAM) as a hole-transporting layer (HTL). A champion efficiency of 23.2%, open-circuit voltage (V) of 1.69 V, and a fill factor (FF) of 78.3% are achieved for the tandem with N2-transferred NiO x :Cu + SAM. The samples with air-transferred NiO x :Cu + SAM have V and FF losses, while those without SAM are heavily shunted. We find via x-ray and UV photoelectron spectroscopy that the air exposure leads to non-negligible loss in the Ni2+ species and changes in the NiO x :Cu’s work function and valence band maxima, both of which can negatively impact the V and the FF of the tandems. Furthermore, by performing dark lock-in thermography, photoluminescence (PL), and scanning electron microscopy studies, we are able to detect various morphological defects in the tandems with poor performance, such as ohmic shunts originating from defects in the bottom CIGSe cell, or from cracking/delaminating of the perovskite top cell. Finally, by correlating the detected shunts in the tandems with PL-probed bottom device, we can conclude that not all defects in the bottom device induce ohmic shunts in the tandems since the NiO x :Cu + SAM HTL bi-layer can decouple the growth of the top device from the rough, defect-rich and defect-tolerant bottom device and enable high-performing devices.

Efficiency Improvement of Industrial Silicon Solar Cells by the POCl3 Diffusion Process

To improve the efficiency of polycrystalline silicon solar cells, process optimization is a key technology in the photovoltaic industry. Despite the efficiency of this technique to be reproducible, economic, and simple, it presents a major inconvenience to have a heavily doped region near the surface which induces a high minority carrier recombination. To limit this effect, an optimization of diffused phosphorous profiles is required. A "low-high-low" temperature step of the POCl3 diffusion process was developed to improve the efficiency of industrial-type polycrystalline silicon solar cells. The low surface concentration of phosphorus doping of 4.54 × 1020 atoms/cm3 and junction depth of 0.31 μm at a dopant concentration of N = 1017 atoms/cm3 were obtained. The open-circuit voltage and fill factor of solar cells increased up to 1 mV and 0.30%, compared with the online low-temperature diffusion process, respectively. The efficiency of solar cells and the power of PV cells were increased by 0.1% and 1 W, respectively. This POCl3 diffusion process effectively improved the overall efficiency of industrial-type polycrystalline silicon solar cells in this solar field.

Metastable Defects Decrease the Fill Factor of Solar Cells

Solar cells are made from semiconductors, which inevitably include defects. The defects in Cu(In,Ga)Se${}_{2}$ (CIGS) are known to be metastable: With excitation they change character, which can have a profound impact on device function. The authors show that these metastable defects reduce the efficiency of the solar cell due to an increased diode factor. It is possible to measure this quantity directly from the bare absorber (without needing to build the entire solar cell), yielding a lower limit for the whole device. Experiments and simulations indicate that metastable defects must be reduced to increase efficiency, and not just in CIGS-based solar cells.

Probing the influence of the passivation layer of 4-Hydroxyphenethylammonium iodide on the optical, structural and solar cell performance of (FAMACs)Pb(IBr)3 perovskite solar cells

Cs0.05FA0.85MA0.10Pb(I0.90Br0.10)3=(FAMACs)Pb(IBr)3 perovskite film was prepared. Using X-ray diffraction, it was determined how the addition of 4-Hydroxyphenethylammonium iodide (4-Hy) layers affected the phases in the produced (FAMACs)Pb(IBr)3 perovskite film. Crystallinity, linear, and nonlinear optical properties of the produced films were analyzed when 4-Hy was added. The electrical and optical conductivity properties of the films were modified through the addition of a 4-Hy passivation layer, and the resulting films were designated for use in a wide range of photovoltaic applications. The optical band gaps (Eg) of all films are between 1.58 and 1.59 eV. The modifications in the nonlinear optical parameters suggest using such films in numerous nonlinear optical devices. The influence of adding 4-Hy to the films on the obtained photoluminescence intensity was also investigated. The power conversion efficiency (PCE), open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF) for the unpassivated perovskite solar cells (PSCs) are 18.29%, 1.043 V, 24.48 mAcm−2, and 71.6%, respectively. For a 4-Hy concentration of 5 mg, a maximum PCE value of 19.12% was obtained, along with VOC value of 1.088 V, JSC value of 23.44 mAcm−2 and FF value of 74.98%.

Synthesis of transparent thermal insulation coating for efficient solar cells

PurposeThe purpose of this paper is to introduce the simple synthesis process of thermal-insulation coating by using three different nanoparticles, namely, nano-zinc oxide (ZnO), nano-tin dioxide (SnO2) and nano-titanium dioxide (TiO2), which can reduce the temperature of solar cells.Design/methodology/approachThe thermal-insulation coating is designed using sol-gel process. The aminopropyltriethoxysilane/methyltrimethoxysilane binder system improves the cross-linking between the hydroxyl groups, -OH of nanoparticles. The isopropyl alcohol is used as a solvent medium. The fabrication method is a dip-coating method.FindingsThe prepared S1B1 coating (20 Wt.% of SnO2) exhibits high transparency and great thermal insulation property where the surface temperature of solar cells has been reduced by 13°C under 1,000 W/m2 irradiation after 1 h. Meanwhile, the Z1B2 coating (20 Wt.% of ZnO) reduced the temperature of solar cells by 7°C. On the other hand, the embedded nanoparticles have improved the fill factor of solar cells by 0.2 or 33.33%.Research limitations/implicationsFindings provide a significant method for the development of thermal-insulation coating by a simple synthesis process and low-cost materials.Practical implicationsThe thermal-insulation coating is proposed to prevent exterior heat energy to the inside solar panel glass. At the same time, it can prevent excessive heating on the solar cell’s surface, later improves the efficiency of solar cell.Originality/valueThis study presents a the novel method to develop and compare the thermal-insulation coating by using various nanoparticles, namely, nano-TiO2, nano-SnO2 and nano-ZnO at different weight percentage.

Relationship between Energetic Disorder and Reduced Recombination of Free Carriers in Organic Solar Cells

AbstractReducing non‐radiative recombination is key to achieve high fill factors (FFs) in organic solar cells. While it is generally accepted that recombination proceeds via charge transfer (CT) states at the donor:acceptor interface, the underlying principles that dictate the decay kinetics of these CT states are not yet well understood. Here, a study on the effect of energetic disorder is presented. Based on a data set of 10 representative donor:acceptor blends, clear correlations between disorder, the recombination coefficient of free charge carriers, and the non‐radiative voltage loss are found. It is suggested that a narrower distribution of CT energies leads to a longer CT decay time and thus reduces non‐radiative losses. This leads to a simultaneous improvement of the FF and open circuit voltage and highlights the importance of having materials with low energetic disorder on the way to the commercialisation of organic photovoltaics.

Naphthalene diimide-based random terpolymers with axisymmetric and asymmetric electron acceptors for controllable morphology and enhanced fill factors in all-polymer solar cells.

All-polymer solar cells (all-PSCs), based on p-type polymer donors and n-type acceptors as the active layer, offer exceptional promise because of excellent thermal stability, superior film formation, and good mechanical stress as a unique bulk heterojunction (BHJ) solar cell combination. Therefore, tuning the molecular composition between polymers is crucial for optimizing power conversion efficiency (PCE) in these all-PSC systems. In this study, we synthesized a series of naphthalene diimide (NDI)-based random terpolymers P(NDI-BDD10), P(NDI-TPD10), P(NDI-TT10), and P(NDI-2FQ10) with axisymmetric (BDD, TPD) and asymmetric (TT, 2FQ) electron acceptors. Compared with the blend morphology of PBDB-T:N2200, their diverse effects due to the addition of trace amounts of axisymmetric and asymmetric components were comprehensively investigated using physical and surface analyses and structural simulations. Consequently, most of our polymer acceptors demonstrated improved fill factors (FFs) in the optimal morphology. P(NDI-BDD10)-based devices achieved the highest PCE of 6.80% and FF of 69.1%, while the architecturally most asymmetric P(NDI-TT10)-based devices reached the lowest PCE of 4.52% despite an enhanced FF of 65.4%. As a result, the appropriate molecular arrangement is crucial for obtaining the desired morphology and improved PCE. Our findings give novel molecular design insight into the distinctions between axisymmetric and asymmetric electron acceptors and seem significant for achieving improved morphological features and efficiency.

Synthesis and Characterization of Zinc Oxide Nanoparticles by Electrochemical Method for Environmentally Friendly Dye-Sensitized Solar Cell Applications (DSSCs)

In this research, zinc oxide nanoparticles (ZnO NPs) were made utilizing an electrochemical method. Which has the advantages of being quick, simple, producing no side products, and being inexpensive. Advanced techniques such as x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis), energy dispersive x-ray (EDX), and atomic force microscopy (AFM) were used to characterize the generated zinc oxide. Using methyl orange dye, the analysis showed that the shape of zinc oxide nanoparticles was rice-like and the band gap value was 3.62. ZnO NPs is used in dye-sensitized solar cells (DSSCs) it has many advantages including its ease of use and low cost, its ability to be integrated into buildings, and its fantastic performance under diffuse and indoor lighting. DSSCs have attracted more attention and have been deemed viable alternatives to conventional photovoltaic devices. The solar cell's efficiency (η %) and fill factor with methyl orange as a dye were 2.3, and 74.1, respectively.

2-Fluoro-4-iodoaniline passivates the surface of perovskite films to enhance photovoltaic properties

An organic molecule, 2-Fluoro-4-iodoaniline (FID), is adopted to passivate the surface defects of (FAPbI3)0.95(MAPbBr3)0.05 perovskite films. The amino group of FID forms a coordinate bond with the uncoordinated lead ion on the perovskite surface via Lewis acid–base interaction, which significantly reduced the defect state density, suppressed carrier nonradiative recombination, and boosted carrier transport of the perovskite films, resulting in increased open circuit voltage (Voc) and fill factor (FF) of the perovskite solar cells (PSCs). Meanwhile, fluorine group of FID forms hydrogen bond with perovskite, restraining ions moving and decomposition of perovskite. Consequently, the power conversion efficiency (PCE) of the PSCs was increased from 21.07% to 23.44%. Moreover, FID passivation also improved the ambient stability of the PSCs. The unencapsulated PSC with FID passivation retained more than 90% of its initial PCE for over 1500 h of storage under ambient conditions.

Quantum Mechanical Assessment of Optimal Photovoltaic Conditions in Organic Solar Cells.

Recombination losses contribute to reducing JSC, VOC, and the fill factor of organic solar cells. Recent advances in non-fullerene organic photovoltaics have shown, nonetheless, that efficient charge generation can occur under small energetic driving forces (ΔEDA) and low recombination losses. To shed light on this issue, we set up a coarse-grained open quantum mechanical model for investigating the charge generation dynamics subject to various energy loss mechanisms. The influences of energetic driving force, Coulomb interaction, vibrational disorder, geminate recombination, temperature, and external bias are included in the analysis of the optimal photovoltaic conditions for charge carrier generation. The assessment reveals that the overall energy losses are not only minimized when ΔEDA approaches the effective reorganization energy at the interface but also become insensitive to temperature and electric field variations. It is also observed that a moderate reverse bias reduces geminate recombination losses significantly at vanishing driving forces, where the charge generation is strongly affected by temperature.

Improving the photovoltaic performance of inverted perovskite solar cells via manipulating the molecular packing structure of PCBM

In this study, the molecular packing structure of solution-processed phenyl-C61-butyric acid methyl ester (PCBM) thin film was manipulated by varying the volume ratio of chlorobenzene (CB) to bromobenzene (BrB) from 100:0 to 50:50, which largely influences the device performance of the PCBM/perovskite heterojunction solar cells. Absorbance spectra, photoluminescence spectra, atomic force microscopic images and contact angle images were used to investigate the molecular packing structure effects of the PCBM thin films on the device performance of the inverted perovskite solar cells. Our experimental results show that the formation of PCBM aggregates and the contact quality at the PCBM/perovksite interface significantly influence the open-circuit voltage, short-circuit current density and fill factor of the resultant solar cells simultaneously. It is noted that the PCE of the encapsulated inverted CH3NH3PbI3 (MAPbI3) solar cells exhibited a stable and high power conversion efficiency of 18%.

24.11% High Performance Perovskite Solar Cells by Dual Interfacial Carrier Mobility Enhancement and Charge‐Carrier Transport Balance

AbstractThe open‐circuit voltage (VOC) and fill factor (FF) of perovskite solar cells (PSCs) are detrimentally weakened by carrier loss at the perovskite/charge transport layers (CTLs) interfaces. Herein, a dual interfacial modification strategy via placing Nb2CTx nanosheets with tailored optoelectrical properties induced by manipulating surface terminal groups at both perovskite/CTLs interfaces is employed. Such tactics not only concurrently implement carrier mobility enhancement of CTLs and interface energy‐levels offsets reduction. More importantly, electrical simulation indicates that the Nb2CTx with O terminal groups located at grain boundaries of the perovskite layer, can more efficiently conduct hole current to the hole transport layer, therefore achieving charge‐carrier transport balance in device. As a result, the synergy effect effectively elevates both the VOC and FF of the cells, reaching maximum values of 1.253 V and 81.07%, respectively, finally delivering progressively increased device power conversion efficiency (PCE) of 24.11% with negligible hysteresis. This PCE value ranks in the highest values to date for PSCs employing MXenes materials. Moreover, the optimized devices show better thermal and light stability than control devices. This work demonstrates a simple and effective dual interfacial modification method utilizing Nb2CTx for photovoltaic field, involving photodetectors, light‐emitting diodes, sensors, etc.

Terpolymers and additional π-bridges regulations for improving fill factors in efficient organic solar cells

For efficient organic solar cells (OSCs), the fill factor (FF) plays a significant role in power conversion efficiency (PCE), which are closely related to molecular stacking and active layer morphology. For polymer design, a feasible strategy to solve this problem is constructing irregular conjugated backbones, such as random terpolymers. In this work, difluorinated benzothiadiazole (SZ) units are introduced into PM7 to synthesize terpolymers. By the SZ units and paired π-bridges, the favorable molecular stacking and active layer morphology can be obtained, which contributes to FF and PCE improving from 61% and 13% of PM7-based OSCs to 71% and 15% of the terpolymer-based OSCs, respectively. Quantum chemistry optimizations reveal that additional π-bridges can adjust the localized planar conformation between the donor and acceptor units. The reduced density gradient function and the independent gradient model approach suggest that different additional π-bridges can promote their effective stacking of SZ units by balancing intra-molecular attraction and repulsion and enhancing intermolecular interactions. This work demonstrates the practicality of terpolymer design and paves a way to improve molecular stacking and morphological properties for efficient OSCs.

Optical simulation and design of high-absorption thin-film perovskite halide solar cells based on embedded quadrilateral cluster nanoparticles

Recently, thin-film organic–inorganic hybrid perovskite solar cells have a high efficiency-to-cost ratio. However, due to the thickness of the absorber layer, photon management in the absorber layer is still not optimized. This research suggests an embedded side for the plasmonic perovskite solar cells. Using Maxwell equations solver (finite-difference time-domain method), numerical optimization of photocurrent for gold, copper, silver, and aluminum cluster of nanoparticles in different geometries including quadrilateral, hexagonal, octagonal, and dodecagonal was investigated at a wavelength range from 300 nm to 800 nm. Moreover, the basic factors of optical simulation such as absorption coefficient, generation rate, and electric field distribution are shown in the optimal case, and the important parasitic absorption challenge for the cluster of nanoparticles was considered in the calculation of the net absorption. The reference cell uses a perovskite absorber (CH3NH3PbI3) with a thickness of 250 nm, which can significantly reduce the amount of lead, and the solar cell's toxicity. The photocurrent density for the optimized case utilizing spherical cluster of nanoparticles is obtained 21.74mAcm−2, which is enhanced by approximately 25.6% compared to perovskite solar cells without nanoparticles. Finally, the best-case cluster nanoparticle is coated with an ultra-thin-film SiO2 layer, to help the chemical and thermal stability of metallic nanoparticles in the photoactive region. According to the final proposed model, the photocurrent of 22.28mAcm−2 and enhancement of 28.72% were obtained. Besides, the proposed solar cell's open-circuit voltage, fill factor, and conversion efficiency are calculated at around 1.003 V, 0.88, and 19.71%, respectively.

Influence of argon pressure on sputter-deposited molybdenum back contacts for flexible Cu(In,Ga)Se2 solar cells on polyimide films

In this study, polyimide films with various thicknesses and coefficients of thermal expansion were used as candidates of lightweight and flexible substrates for Cu(In, Ga)Se2 (CIGS) solar cells. The influence of the Ar background pressure (PAr) during deposition on the properties of the Mo back contact on the polyimide films was investigated. It was found that the stress condition of the Mo contact was the sum of thermal and intrinsic stresses. The thermal stress depended on the coefficient of thermal expansion (CTE) of polyimide films and induced compressive stresses. The intrinsic stress was largely influenced by the PAr. High PAr caused large tensile intrinsic stress and the subsequent formation of cracks in the Mo layer deposited on the polyimide films, whereas no apparent formation of cracks was observed on the reference rigid-glass substrates. The crack formation in Mo deposited on the polyimide films subsequently caused remarkable increase in sheet resistance, which deteriorated the fill factor of the CIGS solar cells. The decreasing PAr reduced the tensile intrinsic stress in the Mo layer, preventing the detrimental crack formation and improving the fill factor of the CIGS solar cells on the flexible polyimide substrates. The stress condition of the Mo was also found to influence thermal diffusion of alkali metal through the contact. The impact of the Mo stress on alkali metal diffusion was adjustable by varying the thickness of alkali silicate thin layers and/or alkali-metal postdeposition treatment conditions, improving conversion efficiency.

Effect of Cd doping on the structural, optical, and photovoltaic properties of SnS films

This paper reports the fabrication of (0 wt. %, 0.5 wt. %, 1 wt. %, 1.5 wt. %, and 2 wt. %) cadmium-doped tin sulphide (Cd-SnS) thin films using sol-gel technique via green synthesis route. Aloe vera gel is used as a green extract to fast fabricate Cd-SnS films. X-ray diffraction (XRD), UV-Vis spectrophotometer, four-point probe method, and J-V measurements are used to determine the crystallographic structure, optical, electrical, and photovoltaic properties, respectively. Here, the detailed structure properties like crystallite size, dislocation line density, d-spacing, and lattice constants of pure and Cd-SnS films are calculated. XRD confirmed the Cd doping in SnS with an orthorhombic structure. The film of 1.5% Cd-SnS showed good structural properties like large crystallite size (29 nm), small d-spacing (2.82 Å), small dislocation line density (1.18 × 1015 m−2), and lattice constants (a = 11.86 Å, b = 3.92 Å, c = 4.33 Å). Optical parameters like bandgap energy (Eg), extinction coefficient (k), refractive index (n), and dielectric constants (n) are calculated by using a UV-Vis spectrophotometer. Cd doped decreased the Eg of SnS. The low value of Eg (1.40 eV) is observed by 1.5% of Cd doping in SnS. A four-point probe approach is used to evaluate the sheet resistivity of Cd-SnS thin films at ambient temperature. The reduced value of sheet resistivity (1.3 × 104 Ω-cm) is achieved at 1.5% Cd doping. Solar cells of these films are fabricated. The geometry of the Cd-SnS solar cell is glass/FTO/TiO2/SnS/P3HT/Au. The open-circuit voltage (Voc), fill factor (FF), efficiency (η), and short circuit current density (Jsc) of solar cells are determined using a J-V curve. For pure SnS based solar cells, Voc is 0.702 V, Jsc is 2.04 mA cm−2, FF is 0.578, and η is 0.82%. All the factors except Voc are increased by Cd doping. The highest efficiency (1.34%) is obtained using a 1.5% Cd-doped SnS film-based solar cell. This efficiency is 61% higher than pure SnS based solar cells. These cells have a low-cost and long life time because there is no chemical corrosion like dye-sensitized solar cells.

Stability and Efficiency Enhancement of Perovskite Solar Cells Using Phenyltriethylammonium Iodide

AbstractControlling the perovskite film surface is key to improving both the stability and photovoltaic performance of perovskite solar cells. In particular, surface defects on the perovskite films, which are fundamental issues, must be passivated. This work presents a 2D organic material phenyltriethylammonium iodide (PTEAI) to passivate a 3D (FAPbI3)1−x(MAPbBr3)x perovskite film surface. PTEAI forms a well‐matched conformal layer on the perovskite film, protecting the film surface from moisture by preventing the escape of organic ions from the film. The N+ cations and I− anions in PTEAI form bonds with the locally charged perovskite surface, reducing the surface defect density as well as the impeding non‐radiative recombination while enhancing carrier lifetimes. These PTEAI features facilitate significant enhancements in both the open‐circuit voltage (VOC) and fill factor (FF) of the perovskite solar cells. As a result, the champion PTEAI‐based perovskite solar cell exhibits the highest power conversion efficiency of 20.2% compared with 18.8% by the pristine device. Additionally, the PTEAI‐treated device retains 92% of its initial efficiency after being stored in ambient air at room temperature and a relative humidity of 40–60% for 500 h without encapsulation.