Lead-free Perovskite Solar Cells Research Articles

Homogenizing The Low-Dimensional Phases for Stable 2D-3D Tin Perovskite Solar Cells.

2D-3D tin-based perovskites are considered as promising candidates for achieving efficient lead-free perovskite solar cells (PSCs). However, the existence of multiple low-dimensional phases formed during the film preparation hinders the efficient transport of charge carriers. In addition, the non-homogeneous distribution of low-dimensional phases leads to lattice distortion and increases the defect density, which are undesirable for the stability of tin-based PSCs. Here, mixed spacer cations [diethylamine (DEA+) and phenethylamine (PEA+)] are introduced into tin perovskite films to modulate the distribution of the 2D phases. It is found that compared to the film with only PEA+, the combination of DEA+ and PEA+ favors the formation of homogeneous low-dimensional perovskite phases with three octahedral monolayers (n=3), especially near the bottom interface between perovskite and hole transport layer. The homogenization of 2D phases help improve the film quality with reduced lattice distortion and released strain. With these merits, the tin PSC shows significantly improved stability with 94% of its initial efficiency retained after storing in a nitrogen atmosphere for over 4600h, and over 80% efficiency maintained after continuous illumination for 400h.

Conformal zinc sulfide coating of vertically aligned ZnO nanorods by two-step hydrothermal synthesis on wide bandgap seed layers for lead-free perovskite solar cells

Vertically aligned ZnO nanorods (NRs) were grown hydrothermally on the wide bandgap (∼3.86 – 4.04 eV) seed layers (SLs) of grain size ∼162 ± 35 nm, prepared using ball-milled derived ZnO powder. The synthesized ZnO NRs were further decorated with ZnS nanocrystals to achieve a ZnO NR-ZnS core–shell (CS)-like nano-scaffolds by a subsequent hydrothermal synthesis at 70 °C for 1 h. UV-Vis-NIR spectroscopy, x-ray diffractometry (XRD), Raman spectroscopy and Field emission scanning electron microscopy (FESEM) coupled with Energy dispersive x-ray spectroscopy (EDX) analyses confirmed the formation of ZnS atop the vertically aligned ZnO NR arrays of ∼1.79 ± 0.17 µm length and ∼165 ± 27 nm diameter. Transmission electron microscopy (TEM)/EDX analyses revealed that vertically aligned ZnO NRs (core dia. ∼181 ± 12 nm) arrays are conformally coated by an ultrathin ZnS (∼25 ± 7 nm) shell layer with a preferential ZnS{111}/ZnO{10-10}-like partial epitaxy. The ZnO NRs exhibited a sharp band edge near ∼384 nm having optical bandgap energy (E g) of ∼3.23 eV. However, the ZnO NR-ZnS CS exhibited double absorption bands at E g ∼ 3.20 eV (ZnO-core) and E g ∼ 3.78 eV (ZnS-shell). The ZnS{111}/ZnO{10-10}-nano-scaffolds could be utilized to facilitate the enhanced absorption of UV photons as well as the radial junction formation between the Pb-free perovskite absorber and ZnS/ZnO NRs layers.

Design and optimization of all-inorganic lead-free perovskite solar cells with RbGeI3/KSnI3 heterojunction structure

Currently, the performance of inorganic and non-toxic perovskite solar cells (PSCs) lags far behind that of organic and Pb-containing PSCs. To enhance the photovoltaic capabilities of inorganic and non-toxic perovskites, a fully inorganic RbGeI3/KSnI3 heterojunction without hole transport layer is proposed, and simulation and optimization are performed using SCAPS-1D software. Research findings indicate that the RbGeI3/KSnI3 perovskite heterojunction significantly improves the quantum efficiency compared to single-layer perovskite, and due to the more matched energy levels, it improves the electric field of the cell and is more conducive to the migration of photogenerated carriers, resulting in excellent device performance. Moreover, PSCs undergo optimization across multiple parameters, including materials for the charge transport layer, perovskite layer thickness, defect density, bandgap, operating temperature, and so on. This comprehensive approach involves analyzing changes in electric field, band structure, and recombination rate. Finally, the power conversion efficiency of the optimized device achieves 40.44 %, marking a significant 440 % increase compared to the 7.49 % efficiency of single-layer PSCs. This work proposes a heterojunction structure to create efficient inorganic and non-toxic perovskite solar cells, providing a novel strategy for further development in this field.

Advanced Optoelectronic Modeling and Optimization of HTL-Free FASnI3/C60 Perovskite Solar Cell Architecture for Superior Performance.

In this study, a novel perovskite solar cell (PSC) architecture is presented that utilizes an HTL-free configuration with formamide tin iodide (FASnI3) as the active layer and fullerene (C60) as the electron transport layer (ETL), which represents a pioneering approach within the field. The elimination of hole transport layers (HTLs) reduces complexity and cost in PSC heterojunction structures, resulting in a simplified and more cost-effective PSC structure. In this context, an HTL-free tin HC(NH2)2SnI3-based PSC was simulated using the solar cell capacitance simulator (SCAPS) within a one-dimensional framework. Through this approach, the device performance of this novel HTL-free FASnI3-based PSC structure was engineered and evaluated. Key performance parameters, including the open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), power conversion efficiency (PCE), I-V characteristics, and quantum efficiency (QE), were systematically assessed through the modulation of physical parameters across various layers of the device. A preliminary analysis indicated that the HTL-free configuration exhibited improved I-V characteristics, with a PCE increase of 1.93% over the HTL configuration due to improved electron and hole extraction characteristics, reduced current leakage at the back contact, and reduced trap-induced interfacial recombination. An additional boost to the device's key performance parameters has been achieved through the further optimization of several physical parameters, such as active layer thickness, bulk and interface defects, ETL thickness, carrier concentration, and back-contact materials. For instance, increasing the thickness of the active layer PSC up to 1500 nm revealed enhanced PV performance parameters; however, further increases in thickness have resulted in performance saturation due to an increased rate of hole-electron recombination. Moreover, a comprehensive correlation study has been conducted to determine the optimum thickness and donor doping level for the C60-ETL layer in the range of 10-200 nm and 1012-1019 cm-3, respectively. Optimum device performance was observed at an ETL-C60 ultra-thin thickness of 10 nm and a carrier concentration of 1019 cm-3. To maintain improved PCEs, bulk and interface defects must be less than 1016 cm-3 and 1015 cm-3, respectively. Additional device performance improvement was achieved with a back-contact work function of 5 eV. The optimized HTL-free FASnI3 structure demonstrated exceptional photovoltaic performance with a PCE of 19.63%, Voc of 0.87 V, Jsc of 27.86 mA/cm2, and FF of 81%. These findings highlight the potential for highly efficient photovoltaic (PV) technology solutions based on lead-free perovskite solar cell (PSC) structures that contribute to environmental remediation and cost-effectiveness.

Numerical investigation of the novel lead-free and eco-friendly InSnCl3-based inorganic perovskite solar cell using SCAPS-1D device simulation

Numerical investigation of the novel lead-free and eco-friendly InSnCl3-based inorganic perovskite solar cell using SCAPS-1D device simulation

Exploring the Bi Layer Approach to Analyzing Lead-Free Perovskite Solar Cells' Numerical Aspects for High Efficiency

In the past decades the metal halide perovskites gained tremendous attention from researchers because of its excellent visible light absorption and promising power conversion efficiencies. But due its toxic nature and concerned ecological hazards it can’t be commercialized on a large scale. So there was a need to introduce a new toxic free alternative. According to this paper a volume lead free perovskite structure is quantitative investigated using SCAPS (1−D) software. A new approach is used in which The lead-free active layer CH3NH3SnI3 is encased in two bilayers of a simultaneous simulation that investigates the hole transport layer (HTL) and electron transport layer (ETL) and fine-tunes their respective thicknesses as well as the absorber layer to attain the best possible performance for the suggested structure. Furthermore, a number of parameters influencing electrical properties were studied statistically, including the effect of different rear connections, temperature changes, doping concentration in the absorber layer, defect states at interfaces, and the overall density of defects. The optimal configuration yielded an open circuit voltage (Voc) of 0.96V, a short circuit current density (Jsc) of 32mA/cm2, a Fill Factor of 82.02, and a power conversion efficiency of 26.09% under standard AM1.5 G conditions.

Restraining Photocurrent Loss of Lead-Free Perovskite Solar Cells by Regulating Surficial Hydroxyl of Fluorine-Doped Tin Oxide

Restraining Photocurrent Loss of Lead-Free Perovskite Solar Cells by Regulating Surficial Hydroxyl of Fluorine-Doped Tin Oxide

Exploring the potential applications of lead-free organic–inorganic perovskite type [NH3(CH2)nNH3]MCl4 (n = 2, 3, 4, 5, and 6; M = Mn, Co, Cu, Zn, and Cd) crystals

The organic–inorganic hybrid perovskite compounds have been extensively studied since the dawn of a new era in the field of photovoltaic applications. Up to now, perovskites have proven to be the most promising in terms of power conversion efficiency; however, their main disadvantages for use in solar cells are toxicity and chemical instability. Therefore, it is essential to develop a hybrid perovskite that can be replaced with lead-free materials. This review focuses on the possibility of applying lead-free organic–inorganic perovskite types [NH3(CH2)nNH3]MCl4 (n = 2, 3, 4, 5, and 6; M = Mn, Co, Cu, Zn, and Cd) crystals. We are seeking organic–inorganic hybrid perovskite materials with very high temperature stability or without phase transition temperature, and thermal stability. Thus, by considering the characteristics according to the methylene lengths and the various transition metals, we aim to identify improved materials meeting the criteria mentioned above. Consequently, the physicochemical properties of organic–inorganic hybrid perovskite [NH3(CH2)nNH3]MCl4 regarding the effects of various transition metal ions of the anion and the methylene lengths of the cation are expected to promote the development and application of lead-free hybrid perovskite solar cells.

Improving Hybrid Tin Halide Films by Tin Trifluoromethanesulfonate for Lead-Free Perovskite Solar Cells.

Tin-based perovskite solar cells (Sn-PSCs) without toxic lead ions outperform other types of lead-free PSCs in terms of photovoltaic performance. To avoid the oxidation of Sn2+ cations and the formation of vacancy defects, most reports involve the addition of SnF2 to the perovskite precursor solution, but hybrid tin halide (Sn-PVK) films still suffer from poor crystallinity and stability. In this work, we used an alternative additive of tin trifluoromethanesulfonate (Sn(OTF)2). Compared to SnF2, the solubility of Sn(OTF)2 in the precursor solution is greatly improved, and the crystal nucleation process is delayed, resulting in the enhancement of crystal growth. The coordination ability of the OTF- anions suppresses the oxidation of Sn2+ cations, which promotes the stability of Sn-PVK films. By replacing the conventional additive of SnF2 with Sn(OTF)2, the device achieves an increase in power conversion efficiency from 7.96% to 10.3%, while the stability of the devices is improved simultaneously.

Highly efficient, low-cost, lead-free bifacial perovskite solar cells: A designing strategy through simulation

The bipolar properties of perovskites make it fascinating to design a perovskite solar cell (PSC) without a hole transport layer (HTL). An HTL-free PSCs provide easy fabrication, are low-cost, and time-saving. In HTL-free PSCs, the crystallinity and morphology of perovskite film can enhance device performance. With the bifacial approach, the device efficiency can be further enhanced. In the present work, HTL-free bifacial PSCs have been simulated, and a strategy has been provided to design a high-performance device. In investigating the effect of various electron transport layers (ETLs) and lead-free perovskite layers, we observed that a suitable combination of ETL and perovskite is vital to achieve a higher power conversion efficiency (PCE). The Mott-Schottky analysis of ETL/perovskite interfaces reveals that the built-in potential depends on the bandgap of the perovskite absorber layer, which affects the device performance by setting up higher open circuit voltage (VOC). A higher dielectric material between the ETL and the perovskite layer improves the device performance. Additionally, lowering the doping density of the perovskite layer increases the bifacial factor of the device. While optimizing our cells, the champion device with configuration FTO/Zn2SnO4/MASnI3/UT-Au (ultra-thin gold) exhibits a PCE of 19.76 % and 15.97 % for the front and rear illumination, respectively. By replacing UT-Au with MAM(MoOx/Ag/MoOx) transparent conducting triple-layer electrode, our device shows an improved PCE of >25 % for both front and rear illumination. The outcomes of these studies are anticipated to be beneficial in designing and optimizing HTL-free bifacial PSCs in the experiment.

Analysis and optimization of lead-free perovskite solar cells: investigating performance and electrical characteristics

AbstractSeveral studies on solar cells using SCAPS-1D were conducted to investigate their performance, which are typically limited to I–V analysis for DC characterization. Therefore, in the present study, a very wide frequency range from 10–2 Hz to 1012 Hz was employed to explore diffusion processes and investigate the performance of lead-free Perovskite Solar Cells (PSCs) featuring as a novel heterostructure. These investigations concern the optimization of MASnI3 thickness as an absorber. Additionally, the impact of series (Rs) and shunt (Rsh) resistances is also examined. From the I–V analysis, it was determined that the power efficiency (PCE) could be achieved at a thickness of 0.6 µm. Increasing the series resistance (Rs) led to a significant decrease in the fill factor (FF) and (PCE), whereas the shunt resistance (Rsh) demonstrated a notable improvement in both (FF) and (PCE). Analysis of AC characteristics revealed complex impedance (Z*) and modulus (M*) indicative of main ionic transport, recombination, and diffusion processes crucial for optimization. An appropriate equivalent circuit model was developed and validated through deconvolution and theoretical considerations, yielding parameters such as the time constant for each process. It was observed that ionic conductivity and electronic diffusion play key roles in balancing charge collection and recombination losses. The critical influence of series and shunt resistance on low and high-frequency processes was emphasized, underscoring their significance in solar cell efficiency. A strong correlation was established between the evolution of time constants for each process and power conversion efficiency (PCE).

Replacing the electron-hole transport layer with doping: SCAPS simulation of lead-free germanium-based perovskite solar cells based on CsGeI3

In recent years, scientists have shown increasing interest in perovskite solar cells because of their remarkable light absorption capabilities and promising prospects, among which germanium-based perovskite solar cells have been praised for non-toxicity. However, the defects between the charge transport layers affect its performance, and the charge transport layer materials also bring environmental hazards due to some organic properties. In this work, we propose to replace the charge transport layer with a solar cell based entirely on the germanium-based perovskite absorption layer by varying the CsGeI3 doping concentration. We created n-CsGeI3 and p-CsGeI3 layers conducive to electron hole transport, thus effectively reducing the defects between the interface transport layers, improving the electron hole transport environment, and improving the transmission efficiency. We employed SCAPS software for designing and optimizing the cell structure, enabling us to model and fine-tune parameters such as band gap, thickness, doping concentration, and defect density. These optimizations led to the calculation of optimal values, resulting in an impressive 34.57 % efficiency. The cell structure developed in this work validates the feasibility of germanium-based perovskite solar cells without electron hole transport layer, reducing environmental risks and optimizing performance parameters to some extent. This provides a valuable reference for future research on such solar cells.

Unraveling the Role of 2D Ti3C2Tx MXene Nanosheets in Cu-Based Double Perovskite Active Layer for Enhanced Photovoltaic Performance.

Although the atmospheric stability of lead-free inorganic double perovskite (DP) solar cells (PSCs) looks promising, their further development is hampered by inadequate film quality and non-radiative carrier recombination at the interfaces. Herein, the incorporation of a newly developed intriguing class of 2D material Ti3C2Tx MXene nanosheets with the photo-absorbing Cu2AgBiI6 (CABI) active layer of a fully inorganic solar cell is reported. The highly conductive Ti3C2Tx nanosheets work as a multi-functional additive by tuning the band gap, reducing the non-radiative carrier recombination, and inhibiting carrier accumulation. In addition, the presence of Ti3C2Tx MXene increases the surface free energy of the perovskite film, which elevates the energy barrier for nucleation and realizes a highly crystalline CABI perovskite film. Primarily, the MXene modification accelerates the charge extraction and transport at the interfaces of the active layer, utilizing energy level alignment with the charge transport layers. Consequently, the photo-conversion efficiency (PCE) of the device with MXene is substantially enhanced to 1.50%. Moreover, the 2D Ti3C2Tx nanosheets increased the long-term stability of the devices by retaining 70% of the initial PCE after 1680 h. With regard to relieving the severe carrier recombination at the interfaces, this work sets a new paradigm toward imminent solar energy conversion.

Optimization of Lead-Free Cs2TiBr6 Green Perovskite Solar Cell for Future Renewable Energy Applications

Optimization of Lead-Free Cs2TiBr6 Green Perovskite Solar Cell for Future Renewable Energy Applications

Studies on the performance of FASnI3:Zn2+-based lead-free perovskite solar cells: A numerical simulation

The search of stable, lead-free absorber material for perovskite solar cells (PSC) resulted in many alternatives, particularly, zinc (Zn) doped formamidinium tin iodide (FASnI3). This work facilitates in investigating the behavior of four different Zn doping ratios 0 %, 2 %, 5 %, and 10 % (say Zn-0, Zn-2, Zn-5, and Zn-10) on the performance of FTO/PCBM/FASnI3:Zn2+/MoOx/Au solar cell structure. A precise evaluation on the impact of the four various Zn doping ratios in the mentioned solar structure in terms of thickness of perovskite absorber layer, hole transport layer, and electron transport layer were executed. The investigation through numerical study further deals with the role of interfacial defect density and capture cross-section of charge carriers on the performance of suggested PSCs with varying Zn doping ratios. It is evident from the optimization results that PSC having absorber layer thickness of 400 nm yields better power conversion efficiency (PCE) of 11.49 % for Zn-5. The PCE is further improved to 13.98 % for capture cross section of 2 ×10−15 cm2. The entire work witnessed distinguishable superior behavior from FASnI3-based PSC doped with Zn ratio: Zn-5 in comparison to the PSCs doped with other Zn ratios. Furthermore, impact of the series and shunt resistances on performance parameters are also examined.

Performance optimization of MASnI3 perovskite solar cells: Insights into device architecture

Recent research has focused an extensive amount of attention on the lead-free substance lead-free methylammonium tin(Sn) tri-iodide (MASnI3), which has emerged as a highly potential absorber layer in the structure of the device. Because it has a larger visible absorption spectrum and a shorter band gap of 1.3 eV than the lead halide perovskite, MASnI3 is a potential alternative to MAPbX3. Through numerical simulation, the different parameters on the device performances are fully investigated. We achieved an open-circuit voltage (Voc) of 0.93 V, a short-circuit current density (Jsc) of 22.20 mA/cm2, a fill factor (FF) of 78.81 %, and a power conversion efficiency (PCE) of 16.39 % using the optimised conditions. It demonstrates the huge potential of recently created lead-free perovskite solar cells and opens up a large dimension of opportunities for the creation of novel perovskite solar cells with a variety of photovoltaic applications. The amalgamation of the Tungsten Disulfide (WS2) material layer between the electron transport layer (ETL) and the absorber layer raised the device module's power conversion efficiency to 20.36 %.

Modeling and performance investigation of novel inorganic Cs4CuSb2Cl12 nanocrystal perovskite solar cell using SCAPS-1D

For the next generation of photovoltaic devices, perovskite solar cells (PSCs) appear as a good choice because they are simple and convert energy to electricity very efficiently. Recent years have seen a great deal of interest in organic-inorganic lead halide perovskites due to their exceptional optoelectronic properties. Nonetheless, additional commercialization of the Pb element is still restricted by its inevitable toxicity. To address the instability and toxicity of the lead hybrid perovskite, it is imperative to produce entirely inorganic lead-free perovskite nanocrystals. Cs4CuSb2Cl12 offers promising qualities and strong stability against light, heat, and humidity to overcome these drawbacks. It possesses an efficient photo-generated carrier and good carrier mobility. In this study, a lead-free perovskite solar cell with the novel configuration of FTO/WS2/Cs4CuSb2Cl12/CuSbS2/Ni has been optimized using SCAPS-1D simulation software and investigates the potential of Cs4CuSb2Cl12 nanocrystal solar cell. The impact of different characteristics of charge transport materials on Cs4CuSb2Cl12 nanocrystal solar cells has been reported. Additionally, the study computationally optimizes the thickness of perovskite layer, doping concentration, defect density, and other input parameters to propose an effective PSC with power conversion efficiency of 23.10 %, Voc of 1.1675V, and FF of 83.33 %.

Perovskite materials with improved stability and environmental friendliness for photovoltaics

Finding innovative, stable, and environmentally acceptable perovskite (PVK) sunlit absorber constituents has developed a major area of study in photovoltaics (PVs). As an alternative to lead-based organic-inorganic halide PVKs, these PVKs are being researched for use in cutting-edge PVK solar cells. While there has been progress in this field as of late, there are still several scientific and technical questions that have yet to be answered. Here, we offer insights into the big picture of PVK toxicity/instability research, and then we discuss methods for creating stable, non-toxic PVKs from scratch. It is also believed that the processing of the proposed PVKs, which occurs between materials design and actual devices, poses novel challenges. PVK PVs that are both stable and ecologically benign can be created if these topics receive more attention. It is interesting to note that although perovskite solar cells (PSCs) have impressive power conversion efficiency, their commercial adoption is hindered by lead toxicity. Lead is a hazardous material that can cause harm to humans and the environment. As a result, researchers worldwide are exploring non-toxic lead-free photovoltaics (PSCs) for a sustainable and safe environment. To achieve this goal, lead in PSCs is replaced by non-toxic or less harmful metals such as tin, germanium, titanium, silver, bismuth, and copper. A study has been conducted that provides information on the characteristics, sustainability, and obstacles of replacing lead with these metals in PSCs. The paper also explores solutions for stability and efficiency issues in lead-free, non-toxic PSC commercialization, including altering manufacturing techniques and adding additives. Lastly, it covers the latest developments/future perspectives in lead-free perovskite solar cells that can be implemented in lead-free PSCs.

A hot phonon bottleneck observed upon incorporation of SnF2 to MASnI3 films and its possible role in increasing photocarrier diffusion length

While SnF2 is reported as an effective additive for improving the efficiency of lead-free tin-based perovskite solar cells, the mechanism is still unclear and requires further studies. Upon incorporating SnF2 into MASnI3, SnF2 reduces the intrinsic carrier density from 1018 to 1012 cm–3 and produces a longer carrier diffusion length as confirmed by the Hall measurements. The femtosecond transient absorption spectroscopy shows that SnF2 doping enhances the hot-phonon bottleneck effect of MASnI3. The slow cooling process of hot carriers may help to reduce non-radiative recombination, increase the fluorescence lifetime, and, therefore, improve the utilization rate of carriers. Finally, lead-free low bandgap perovskite MASnI3 is utilized as a light absorbing layer in solar cells, achieving high optical current and high voltage in tin-based perovskite solar cells. The final power conversion efficiency is 10.2%, while the power conversion efficiency for the control unit is 6.69%.

Spin-coated high mobility MoO3 thin film for designing highly efficient lead-free perovskite solar cells

Among the thin film-photovoltaics, perovskite solar cells (PSCs) are one of the most developing topics of research in recent times. Research records reveal that around 26 % efficiency in PSCs has already been achieved so far. However, the commercialization of those PSCs is hindered due to the toxicity of lead (Pb), and the instability of organic cations as well as structural volatility. Several inorganic materials including inorganic hole transport layer (HTL) have recently been proposed and developed to reduce the organic part in the device structure. We fabricate MoO3 thin film materials and conduct a detailed study to realize the potential of MoO3 as a unique HTL for application in PSCs. The synthesis of MoO3 thin film includes several characterization techniques e.g. XRD, FESEM, EDX, UV–Vis, and Hall Effect measurement. We design a MoO3 thin film-based, lead-free PSC structure of FTO/MoO3/PTAA/(FA)2BiCuI6/ZnO/Ag and perform numerical analysis using the SCAPS-1D simulation tool. In the device simulation process, we use the experimentally obtained optoelectrical properties of the MoO3 film and achieve a maximum efficiency of around 22.28 % in a contained lead-free PSC.