An analysis comparing the performance of lead and tin halides organic Perovskite Solar Cells and numerical simulation with SCAPS

Lead-free tin perovskite solar cells

Design and simulation of efficient tin based perovskite solar cells through optimization of selective layers: Theoretical insights

Organometal hybrid perovskite material has emerged as an attractive competitor in the field of photovoltaics due to its promising potential of low-cost and high-efficiency photovoltaic applications. Although organometal halide perovskite solar cell shows great potential to meet future energy needs, the degradation raises serious questions about its commercialization viability. At present, the stability of perovskite solar cells has been studied in various environmental conditions. Nonetheless, an understanding of the degradation and its performance of CH3NH3PbI3-xClx perovskite solar cell is limited. Herein, we report the mechanical and structural degradation of CH3NH3PbI3-xClx perovskite films at room temperature as a function of time and thermal instability of perovskite solar cells during the heating and cooling processes. For mechanical degradation measurement, we used nanoindentation for CH3NH3PbI3-xClx perovskite films fabricated on FTO/PEDOT:PSS substrate. The hardness and elastic modulus of perovskite films were measured as a function of time. In addition, the mechanical degradation of perovskite thin films was correlated with X-ray diffraction, steady-state and time-resolved photoluminescence (PL). We also investigated the thermal instability of perovskite thin films and the irreversible performance of perovskite solar cells. Particularly, the irreversible performance of CH3NH3PbI3-xClx was analyzed by measuring the development of crystallinity, charge trapping/detrapping, trap depth, and PbI- phase while varying the temperature of perovskite films and solar cells between room temperature and 82 °C. Surprisingly, we found that the degradation of both perovskite films and solar cells occurred at ~70°C. Remarkably, even after the perovskite solar cell temperature cooled down to room temperature, the performance of solar cells continuously degraded. The underlying mechanism of irreversibly degraded performance of perovskite films and solar cells were explained in terms of the development of phase separation, increased trapping rates and deep trap depth of defect states of perovskite films.

Decoupling the effects of defects on efficiency and stability through phosphonates in stable halide perovskite solar cells

In this work the one dimensional device simulation of lead-free perovskite solar cell of CH 3 NH 3 SnI 3 absorber perovskite material is performed. The parameters which affect the overall performance of the solar cell are investigated and it is observed that the absorber thickness, doping concentrations of HTM (hole transport material), ETM (electron transport material) and perovskite absorber and temperature, influence the solar cell performance. The optimized performance of the perovskite solar cells with PCE (power conversion efficiency) of 30.59%, is obtained when the thicknesses of perovskite was 300nm and the doping concentrations of Cu2O, PCBM and perovskite were 9×1021cm-3, 1×1021cm-3 and 1×1013cm-3 respectively. It is observed that suitable optimization of material parameters and device dimensions may lead to high efficiency Perovskite solar cell.

Perovskite solar cells have rapidly revolutionized the photovoltaic research showing an im-pressively dynamic progress on power conversion efficiency from 3.8 to 22% in only several years, a record for a nascent technology. Furthermore, inexpensive precursors and simple fabrication methods of perovskite materials hold a great potential for future low-cost energy generation enabling the global transition to a low-carbon society. The best performing device configuration of perovskite solar cell is composed of an electron transporting material, typi-cally a mesoporous layer of titanium dioxide, which is infiltrated with perovskite material and coated with a hole transporting material. However, although perovskite solar cells have achieved high power conversion efficiency values, there are several challenges limiting the industrial realization of low-cost, stable, and high-efficiency photovoltaic devices. To date, spiro-OMeTAD and PTAA are hole transporting materials of choice in order to main-tain the highest efficiency, however, the prohibitively high price hinders progress towards cheap perovskite solar cell manufacturing and may contribute to more than 30% of the overall module cost. Additionally, such wide bandgap hole transporting materials typically require doping in order to match necessary electrical conductivity and the use of additives is prob-lematic, since hygroscopic nature of doping makes the hole transporting layer highly hydro-philic leading to rapid degradation, negatively influencing the stability of the entire device. In order to overcome these problems, the rational design, synthesis, and characterization of a variety of small molecule-based hole transporting materials have been on a focus of this the-sis. Through judicious molecular engineering four innovative hole transporting materials KR131, KR216, KR374, and DDOF were developed via alternative synthetic schemes with the minimized number of steps and simple workup procedures allowing cost-effective upscale. Employing various characterization methods, the relationship between the molecular struc-ture of the novel hole transporting materials and performance of perovskite solar cells was investigated, leading to a fundamental understanding of the requirements of the hole trans-porting materials and further improvement of the photovoltaic performance. Furthermore, the synthesis of the dopant-free hole transporting materials based on push-pull architecture is presented. Highly ordered characteristic face-on organization of KR321 hole transporting molecules benefits to increased vertical charge carrier transport within a perov-skite solar cell, leading to a power conversion efficiency over 19% with improved durability. The obtained result using pristine hole transporting material is the highest and outperforms most of the other dopant-free hole transporting materials reported to date. Highly hydropho-bic nature of KR321 may serve as a protection of perovskite layer from the moisture and pre-vent the diffusion of external moieties, showing a promising avenue to stabilize perovskite solar cells.

A comparative theoretical study on the performance of perovskite solar cells (PSCs) with methyl ammonium lead iodide (MAPbI3) and methyl ammonium germanium iodide (MAGeI3) as absorber layers is reported by modeling the solar cells for a number of electron transport materials (ETMs), hole transport materials, and back‐contact metals using solar cell capacitance simulator 1D tool. For MAPbI3 as the absorber layer, the best photovoltaic performance is observed for the configuration glass/fluorine‐doped tin oxide (FTO)/SnO2/MAPbI3/NiO/Au with a power conversion efficiency (PCE) of 20.58% and a fill factor (FF) of 68.34% and for MAGeI3, the configuration glass/FTO/SnO2/MAGeI3/CuO/Pd exhibits the best performance with a PCE of 13.12% and a FF of 68.29%. This study indicates that the low‐cost metal oxide SnO2 is a better substitute for the commonly used TiO2 as ETM, and the metal oxides like NiO and CuO provide a higher PCE for device configurations with MAPbI3 and MAGeI3, respectively, as the absorber layer. The low‐cost back‐contact metal Pd provides a better performance for MAGeI3‐based PSCs. This study also indicates that the nontoxic MAGeI3‐based PSCs can be used for commercial applications as they are more thermally stable than the MAPbI3‐based PSCs and provide an equally good quantum efficiency curve as that of MAPbI3‐based PSCs.

The SCAPS-1D simulation tool was employed to conduct photoelectric simulation of perovskite solar cells in this paper. To begin with, a MAPbI3/MASnI3 layer was used as the perovskite absorption layer to investigate the performance of tandem perovskite solar cells. The influence of defect density and the work function of the front electrode on the device performance were studied. Additionally, the impact of temperature variations on device performance was studied. The results indicate that the MAPbI3/MASnI3 tandem perovskite solar cells achieve higher efficiency (30.05%) than the single-junction perovskite solar cells. Moreover, low defect density and temperature were found to be beneficial for higher performance. The heat distribution inside the device was studied using the finite element method. Furthermore, the influence of different hole transport materials and electron transport materials on the performance of perovskite solar cells with the hybrid perovskite layer (MAPbI3/MASnI3) was investigated and find out the appropriate transport layer materials. This research provides a reference for the perovskite solar cells.

The absorbing layer thickness is a crucial parameter that significantly impacts the performance of perovskite solar cells (PSCs). In this study, we investigated the influence of the thickness of absorbing layer on the performance of silver-doped NaZnBr3 perovskite solar cells using the one-dimensional solar cell capacitance simulator (SCAPS-1D) software. The absorbing layer thickness was varied in the range of 0.1 to 1.3 µm. The initial solar cell after simulation gave an open-circuit voltage (Voc) of 1.174 V, short circuit current density (Jsc) of 14.012 mA/cm2, fill factor (FF) of 79.649%, and the power conversion efficiency (PCE) of 13.101%. For the optimized thickness of the perovskite layer of 1.0 µm, the following solar cell characteristics were obtained: Voc = 1.197 V, Jsc = 18.184 mA·cm–2, FF = 79.110%, and PCE = 17.215%. A 31% and 30% increase of the PCE and Jsc, respectively, was observed for the optimized device parameters as compared to the initial ones. Such finding confirms the premise for excellent photon management and enhancement of PSCs performance by selecting the thickness of absorbing layer.

In recent years, perovskite solar cells have obtained a rapid development due to their large light absorption coefficient, low-cost and high power conversion efficiency (PCE). In this study, the one-dimensional ordered ZnO nanorod arrays were prepared on FTO glasses by chemical bath deposition at low temperature. TiO2 nanoparticles from different kinds of solution were further spin-coated onto the ZnO nano arrays to form ZnO/TiO2 composite nano arrays, as the electron transfer layer in perovskite solar cells. The microstructure of different ZnO/TiO2 composite nano arrays and their corresponding photovoltaic performance of the solar cells were investigated. It was found that the cells based on ZnO nano arrays treated by TiO2 nanoparticle paste exhibit the highest PCE. The influence of TiO2 paste concentration on the photovoltaic performance of cells was further investigated. It indicated that the cell achieves best photovoltaic performance at TiO2 paste concentration of 0.1 mol/L: open circuit voltage ( V oc) of 0.93 V, short circuit current ( J sc) of 15.30 mA cm−2, filling factor ( FF ) of 43% and PCE of 6.07%. The treatment of TiO2 paste on ZnO nano arrays results in perovskite nanoparticles can effectively fill into the cracks between ZnO nanorods and a flat and compact perovskite layer can also form on the top of ZnO nano arrays. These effectively enhance the loading of perovskite and suppress the recombination between carriers in cells, resulting in an improved photovoltaic performance. A further treatment of ZnO/TiO2 paste arrays with TiCl4 aqueous solution can significantly improve the photovoltaic performance of the perovskite solar cells: V oc=0.99 V, J sc=19.09 mA cm−2, FF =58%, and PCE of 11%. The TiCl4 treatment of ZnO/TiO2 composite arrays introduces small TiO2 nanoparticles (~3 nm) into nano arrays. The small nanoparticles can fully fill the cracks between the nanorods and create better contact between perovskite (both in top layer and the arrays) and nano arrays. The photo induced carrers can rapidly transfer via ZnO nanorods to the conductive substrates. Furthermore, the introduce of small TiO2 nanoparticles also increases the surface area of electrode to absorb more perovskite, and hence improve the adsorption of light and result in an improved photovoltaic performance of the cells.

Parasitic optical losses, including free-carrier absorption and absorption from the rear mirror, could significantly affect the performance of solar cells. Although estimates of their influence have been made in the past, they have not previously been incorporated into the absorptivity of semiconductor materials and their influence on the performance of perovskite solar cells studied quantitatively. This paper numerically investigates the impact of both typical kinds of parasitic optical losses on the performance of perovskite solar cells utilizing the detailed balance model. It is found that the free carrier absorption loss has nearly no influence on the performance of perovskite solar cells, but parasitic absorption at the rear mirror can significantly affect the performance of solar cells. For thin film perovskite solar cells, parasitic absorption significantly affects the short circuit current, open circuit voltage and power conversion efficiency (PCE), but for thick solar cells, the short circuit current is nearly independent of the parasitic absorption; it seriously affects the open circuit voltage and PCE.

Hole transport material (HTM) plays an important role in the efficiency and stability of perovskite solar cells (PSCs). Spiro-MeOTAD, the commonly used HTM, is costly and can be easily degraded by heat and moisture, thus offering hindrance to commercialize PSCs. There is dire need to find an alternate inorganic and stable HTM to exploit PSCs with their maximum capability. In this paper, a comprehensive device simulation is used to study various possible parameters that can influence the performance of perovskite solar cell with CuI as HTM. These include the effect of doping density, defect density and thickness of absorber layer, along with the influence of diffusion length of carriers as well as electron affinity of electron transport layer (ETM) and HTM on the performance of PSCs. In addition, hole mobility and doping density of HTM is also investigated. CuI is a p-type inorganic material with low cost and relatively high stability. It is found that concentration of dopant in absorber layer and HTM, the electron affinity of HTM and ETM affect the performance of solar cell minutely, while cell performance improves greatly with the reduction of defect density. Upon optimization of parameters, power conversion efficiency for this device is found to be 21.32%. The result shows that lead-based PSC with CuI as HTM is an efficient system. Enhancing the stability and reduction of defect density are critical factors for future research. These factors can be improved by better fabrication process and proper encapsulation of solar cell.

Enhancing photovoltaic performance of carbon-based perovskite solar cells by introducing plasmonic Au NPs

High-performance methylammonium-free ideal-band-gap perovskite solar cells

Abstract4‐Tert‐butylpyridine (tBP) is an important additive in triarylamine‐based organic hole‐transporting materials (HTMs) for improving the efficiency and steady‐state performance of perovskite solar cells (PVSCs). However, the low boiling point of tBP (196 °C) significantly affects the long‐term stability and device performance of PVSCs. Herein, the design and synthesis of a series of covalently linked Spiro[fluorene‐9,9′‐xanthene] (SFX)‐based organic HTMs and pyridine derivatives to realize efficient and stable planar PVSCs are reported. One of the tailored HTMs, N2,N2,N7,N7‐tetrakis(4‐methoxyphenyl)‐3′,6′‐bis(pyridin‐4‐ylmethoxy) spiro[fluorene‐9,9′‐xanthene]‐2,7‐diamine (XPP) with two para‐position substituted pyridines that immobilized on the SFX core unit shows a high power conversion efficiency (PCE) of 17.2% in planar CH3NH3PbI3‐based PVSCs under 100 mW cm−2 AM 1.5G solar illumination, which is much higher than the efficiency of 5.5% that using the well‐known 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxy‐phenyl‐amine)9,9′‐spirobifluorene (Spiro‐OMeTAD) as HTM (without tBP) under the same condition. Most importantly, the pyridine‐functionalized HTM‐based PVSCs without tBP as additive show much better long‐term stability than that of the state‐of‐the‐art HTM Spiro‐OMeTAD‐based solar cells that containing tBP as additive. This is the first case that the tBP‐free HTMs are demonstrated in PVSCs with high PCEs and good stability. It paves the way to develop highly efficient and stable tBP‐free HTMs for PVSCs toward commercial applications.