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This computational study investigated a lead (Pb)-free ethyl ammonium (EA) substituted ethylenediamine (EDA) based ((FA 0.9 EA 0.1) 0.98 EDA 0.01 SnI 3) perovskite solar cell (PSC) using the solar cell capacitance one-dimensional simulator (SCAPS 1D). The initial device schematic comprised ((FA 0.9 EA 0.1) 0.98 EDA 0.01 SnI 3) based perovskite as an absorber layer with copper (I) oxide (Cu 2 O) and [6,6] phenyl-C61 butyric acid methyl ester (PCBM) as hole and electron transport layers, where the device efficiency was 21.87%. The impacts of numerous electron transport layers (ETLs) and hole transport layers (HTLs) were also examined. The charge transport layers were optimized based on their energy levels and according to the relationship between the built-in potential (V bi) and the open-circuit voltage (V OC). Numerical simulations showed that to circumvent the V bi loss, the valence band (VB) maximum of HTL (E VB_HTL) should not be lower than the VB for perovskite (PVK) (E VB_PVK) for the appropriate selection of HTLs. Correspondingly, for the suitable selection of ETLs, the conduction band (CB) minimum of ETL (E CB_ETL) and the front contact should not be greater than the CB minimum for PVK (E CB_PVK). Therefore, the optimized ETLs and HTLs were obtained as zinc oxysulfide and copper (II) phthalocyanine, respectively, where the device's efficiency increased up to 22.36%. The effect of the thickness of the EDA-based PSCs was also examined and the optimized thickness was obtained as 1.1 μm, where the device's efficiency increased to 24.42%. This improvement in the performance of the device indicates that EA substituted EDA-based ((FA 0.9 EA 0.1) 0.98 EDA 0.01 SnI 3) PSC is a promising alternative for use in Pb-free PSCs. • The simulation of the lead-free ethylenediamine based ((FA 0.9 EA 0.1) 0.98 EDA 0.01 SnI 3) perovskite solar cell is performed. • The charge transport layers are optimized co-relating the built-in potential and the open circuit voltage. • The band alignment between ETL/perovskite & perovskite/HTL depicts a significant impact on the device performance. • The CuPc and ZnOS as a hole and electron transport layer elevate the device efficiency up to 22.36 %. • At the optimized thickness of the perovskite layer, the device efficiency improves up to 24.42%. [ABSTRACT FROM AUTHOR]

High electrical conductivity and superior redox properties of metal sulfide-based supercapacitors have attracted much attention in recent years. The simple and cost-effective method in the fabrication of high-performance supercapacitors is currently in high demand. In this paper, low-cost one-dimensional copper sulfide (Cu2S) electrodes are synthesized on glass as well as on flexible substrates such as polyethylene terephthalate (PET) and polypropylene (PP). The effect of the deposition quantity of Cu2S-1:1 on the glass substrate is also discussed. The synthesis of copper sulfide was done at room temperature by reducing copper sulphate pentahydrate using ascorbic acid as a reducing agent in sodium thiosulphate with 2 h of total reaction time. Scanning electron microscopy and x-ray diffraction characterizations are performed to validate the formation of Cu2S hollow rods. Electrochemical measurements such as cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy are performed using a Metrohm Autolab workstation. Cyclic voltammetry is performed to measure the capacitance of Cu2S-based supercapacitors in which the ratio of copper sulphate and sodium thiosulphate was varied from 1:0.5 to 1:1.5 with a step size of 0.5, and the deposition quantity of Cu2S-1:1 film was also varied on glass substrate from 1 mg to 2 mg. The results show that the device with a 1:1 ratio shows the highest capacitance, i.e., 587 mF/cm2 as compared to the devices fabricated with a 1:0.5 ratio, 1:1.5 ratio, and 1:1 ratio with greater deposition. This is mainly because the 1:1 ratio has less resistance and has a hollow rod structure which allows the electrolyte ions to penetrate in Cu2S active material and thus, facilitates fast electron transport resulting in high-performance supercapacitors. Further, to understand the increased capacitive properties of a copper sulfide-based supercapacitor, processes involving charge transfer and mass transport are investigated by performing electrochemical impedance spectroscopy (EIS). The radius on the EIS plot of Cu2S-1:1 is smaller as compared to the other three samples on the glass substrate. Also, the resistance of Cu2S-1:1 with greater deposition is more than the Cu2S-1:1 sample because the increased amount of electrode material leads to increased paths for the electrolyte ions to interact with the electrode material. Further, this paper also discusses the successful fabrication of the supercapacitor devices on flexible PP substrate using 1-D Cu2S for the first time. The results show that the capacitance value on the flexible substrate is on par with that of glass substrates. Also, the synthesized copper sulfide 1:1 sample exhibits excellent stability with the capacitance retention of 85.7%, 91.1%, 86.18%, and 92.8%, respectively, on PP, glass, PET, and Cu2S-1:1 with more deposition on glass substrate after 3500 cycles. [ABSTRACT FROM AUTHOR]

• All- perovskite lead –free tandem solar cell is simulated with efficiency 26.73%. • CH 3 NH 3 GeI 3 & FAMASnGeI 3 perovskite layers have been used. • Different elctron transport layers have been studied. • The impact of defect density and front electrode work function is also studied. The numerical simulation of lead-free all-perovskite tandem solar cell using solar capacitance one dimensional tool (SCAPS 1D) has been performed. The combination of methyl ammonium germanium halide (CH 3 NH 3 GeI 3) as wide band-gap (1.9 eV) perovskite layer and FA 0.75 MA 0.25 Sn 0.25 Ge 0.5 I 3 (FAMASnGeI 3) as a low band-gap (1.4 eV) perovskite layer is considered for the first time which shows the optimal device efficiency of 26.72%. The present work studies the effect of the different electron transport layer, perovskite absorber thickness and its defect density on photovoltaic performance. Further, the effect of front electrode work function on the device photovoltaic performance is also studied. It has been observed that the device open circuit voltage (Vo C) is significantly affected by the built-in voltage (V bi) across the perovskite layer. In addition, the effect of thickness of the perovskite absorber layers is also investigated. Moreover, the effect of defect density of the absorber layer is also explored, and it has been found that for better device performance the defect density needs to be as low as possible. Furthermore, it has been observed that the work function of the front contact plays a significant role and for the proposed device its value should not be more than 4.4 eV. The proposed all–perovskite tandem solar cell shows the remarkable photovoltaic parameters i.e., open circuit voltage (V OC) = 1.07 Volts, short circuit current density (J SC) = 28.36 mA/cm2, fill factor (FF) = 84.39% and efficiency (η) = 26.72%. [ABSTRACT FROM AUTHOR]

The present study investigates the effect of band offsets engineering for lead–free (Pb-free) all-inorganic double-perovskite solar cell (DPSC) using the solar cell capacitance simulator one dimensional (SCAPS 1D). The initial simulation study is carried out by using Cs 2 AgBi 0.75 Sb 0.25 Br 6 based double-perovskite layer along with 2,2′,7,7′-tetrakis[N,N-di4-methoxyphenylamino]-9,9′-spirobifluorene (SpiroOMeTAD) as a hole transport layer (HTL) and zinc oxide (ZnO) as an electron transport layer (ETL) which shows the device efficiency of 11.35%. Further, the impact of the conduction band offset (CBO) and valence band offset (VBO) is studied to improve the device performance. The proposed study suggests that extremely negative and positive CBO resulted in limited PV performance. This is mainly due to the reason that in extremely negative CBO limits the V bi and thus V OC. However, the extreme positive CBO leads to the formation of a barrier spike which restricts the device performance. Similarly, the positive VBO leads to band misalignment which further deteriorates the device performance. Hence, it has been revealed from the numerical simulation, that the optimum conduction band offset (CBO) is found to be −0.1 eV to +0.1 eV and the optimum valence band offset (VBO) is found to be −0.1 eV–0.00 eV with respect to the double-perovskite absorber layer. It has been found that with the introduction of copper (I) thiocyanate (CuSCN) as a hole transport layer (HTL) and zinc oxysulfide (ZnOS) as an ETL the overall power conversion efficiency (PCE) improves up to 18.26% which is an outstanding improvement in the lead-free double–perovskite solar cell. In addition, the effect of the thickness of the perovskite layer is also studied in which the optimized double-perovskite layer thickness obtained is 400 nm. Thus, the proposed simulation study provides significant insight for the researchers that will help to find out the suitable ETL and HTL for Pb-free DPSC. • Band offset engineering is analyzed to improve the performance of double–perovskite solar cells. • The range of optimum CBO and VBO is obtained is −0.1eV–0.1eV and −0.1 eV–0.00 eV respectively. • The effect of thickness of the Pb-free double-perovskite layer on the photovoltaic performance is also investigated. • The final device efficiency of double–perovskite solar cell reaches up to 18.26%. [ABSTRACT FROM AUTHOR]

This article presents the numerical simulation of lead–free (Pb-free) double–perovskite (Cs 2 AgBi 0.75 Sb 0.25 Br 6 , i.e., mixed antimony bismuth halide double-perovskite) solar cell (DPSC) using solar cell capacitance one dimensional simulator (SCAPS-1D). In this contribution, the hole transport layers (HTLs) and electron transport layers (ETLs) are optimized. The optimization is performed by correlating the open circuit voltage (V OC) with the built-in potential (V bi). It is disclosed from the simulation results, that higher V bi resulted higher V OC. Furthermore, it is also found that, for the proper selection of HTL, the E V_HTL (Valence band maximum of HTL) and φ BC (Work function of back contact) should not be much deeper than the E V_PVK (Valence band maximum of double–perovskite layer) to avoid V bi loss. Correspondingly, for proper selection of ETL, E C_ETL (Conduction band minimum of electron transport layer) and Φ FC (Work function of front contact), should not be much higher than E C_PVK to prevent V bi loss. The optimized HTL and ETL are found to be Cu 2 O (copper(I) oxide) and ZnOS (Zinc oxysulfide) respectively. Moreover, the device photovoltaic performance is further improved by optimizing the double-perovskite layer thickness which is found to be 400 nm. Under optimized condition, the device photovoltaic power conversion efficiency (η) improves to 18.18%. The optimized device photovoltaic performance are found to be, open –circuit voltage (Voc) = 1.39 V, short-circuit current density (J SC) = 16.04 mA/cm2, and fill factor (FF) = 78.34% which indicates that double–perovskite absorber layer (Cs 2 AgBi 0.75 Sb 0.25 Br 6) is a suitable candidate for the development of highly efficient Pb-free DPSC. • The numerical simulation of lead-free double–perovskite is performed with-optimized device efficiency of 18.18%. • The electron transport layer and hole transport layer is optimized by co-orelating V OC with V bi. • The simulation study reveals that V OC is strongly dependent on V bi of lead-free double –perovskite absorber layer. • The optimized ETL and HTL found to be ZnOS and Cu 2 O respectively. [ABSTRACT FROM AUTHOR]

The numerical simulation of lead-free perovskite cesium tin germanium halide (CsSnGeI 3) and methyl ammonium germanium halide (CH 3 NH 3 GeI 3) solar cells have been performed. It has been elucidated from the numerical simulation that as compare to the CH 3 NH 3 GeI 3 based structure, CsSnGeI 3 based structure depicts better photovoltaic performance under constant illumination condition. To enhance the device photovoltaic performance, the effects of different hole transport layer (HTL), defect density of the absorber layer, metal work function and the effect of temperature has been studied. In the present investigation, the effect of hole transport layers are analyzed by correlating the built-in voltage (V bi) with the open circuit voltage (V OC). It has been obtained from the simulation results, that V bi has a significant impact on V OC as the higher V bi corresponds to the highest V OC. Moreover, the effect of defect density and metal work function is also studied. It is obtained from the simulation results, that the optimum defect density is found to be 1 × 1014 cm−3 and metal work function should be greater than or equal to 5 eV for both lead-free CH 3 NH 3 GeI 3 and CsSnGeI 3 based perovskite layer. Furthermore, to suggest possible lead-free alternatives for all-perovskite two-terminal multi-junction solar cell, an attempt is made to match the current of bottom perovskite layer i.e., CsSnGeI 3 based perovskite layer to the top perovskite layer i.e., CH 3 NH 3 GeI 3 based perovskite layer. To attain the current matching for bottom perovskite layer (CsSnGeI 3 based perovskite layer) to top perovskite layer (CH 3 NH 3 GeI 3 based perovskite layer), the bottom perovskite sub cell is fed with the filtered spectrum which is obtained by transmission from top electrode. After, the realization of current matching the short circuit current density of CsSnGeI 3 based perovskite layer drops from 25.75 mA/cm2 to 15.32 mA/cm2 which is similar to CH 3 NH 3 GeI 3 based perovskite absorber layer. In addition, it has been obtained from literature, that both the perovskite layers can be fabricated using solution–processing low-temperature technology. Hence, the numerical study suggests the possible alternatives for wide and narrow bandgap perovskite layers for the application to obtain highly efficient lead-free all-perovskite multi-junction solar cells. • The numerical simulation of lead-free wide and narrow bandgap CH 3 NH 3 GeI 3 and CsSnGeI 3 perovskite layers is performed. • The effect of different hole transport layers is realized by correlating V bi with the V OC. • Cu 2 O as an HTL shows highest V bi and hence shows better photovoltaic performance. • The study of defect density, metal work function and temperature are explored for lead-free perovskite layers. • The lead-free perovskite layers proves to be the promising candidate for all-perovskite multi-junction solar cell. [ABSTRACT FROM AUTHOR]