Developing Lead-Free Perovskite-Based Solar Cells with Planar Structure in Confined Mode Arrangement Using SCAPS-1D

Abstract

In this work, the SCAPS-1D solar cell simulation software was used to model, simulate and track perovskite solar cells (PSCs) with planar structure, in a confined mode arrangement (FTO/TiO/CH₃NH₃PbI₃/CH₃NH₃GeI₃/CH₃NH₃SnI₃/CuO₂). Different compositions, absorber thickness, electron affinity, and absorber doping concentration were investigated. Different hole transport materials (CuO₂, CuI, NiO, PEDOT: PSS) were used. The best result for CH₃NH₃PbI₃ with CuO₂ hole transport material (HTM) showed an overall efficiency of 18.28%, FF of 62.71%, Jsc of 25 mA/cm², and Voc of 1.1 V. For tin lead-free halide CH₃NH₃SnI₃, the best results showed an overall efficiency of 24.54%, FF of 71.30%, Jsc of 34 mA/cm², and Voc of 0.99 V. Lead-free PSC has an advantage over lead PSC due to lead toxicity. However, a tin-based cell is unstable, hence, the p-type carrier doping concentration of tin-based perovskite PCE of the device can be improved due to the better and stronger combined electric field.

1. Introduction

Modern trends in renewable energy show a range of promising new technologies and innovative chemical and physical processes, as well as, new systems for generating, converting, transmitting, and conserving energy. Today there is nothing more important than the energy with an evident impact on the sustainability of human civilization. Although global fossil fuel resources such as coal, oil, and natural gas have not yet been depleted, the negative social, health and environmental impacts on our present society are already becoming particularly harmful to the environment. These alternative and new methods give large-scale opportunities to produce the vast amounts of energy needed to maintain our current development. Cells, whether they are organic or inorganic solar cells are semiconductor materials. Basically, semiconductor materials made of organic molecules have some similarities to first-generation and second-generation solar cells, in function but different in materials. In solving the problem of organic solar cells, SCAPS-1D simulation software has been used in several simulation-based perovskites solar cells (PSCs) [1].

Simulation methods can help clarify the phenomena existing in solar cells. In order to gain the best and agreed understanding, a theoretical study using SCAPS software was conducted by Sajid et al., [2], and a planar PSC configuration (FTO/TiO₂/MAPbI₂Br/HTM/Au) was simulated as a baseline. A numerical analysis was performed to find the optimum conditions for PSCs with inorganic HTMs, and factors that affected the performance of PSCs were investigated. According to the simulation results, the optimal electron affinity, hole mobility, and acceptor density of CuO₂ were found to be 3.2 eV, 60 to 100 cm²V⁻¹s⁻¹, and 10¹⁸ cm⁻³, respectively. Moreover, The simulation findings showed that a matched valance energy band of CuO₂ resulted in improvements in the performance of the PSCs, whereas an unmatched valance energy band of CuO₂ led to a high charge recombination rate and poor device performance. The PCE of 25.2% was attained under optimal conditions, demonstrating that CuO₂-based PSCs are promising [2].

CsPbI₃ has recently received tremendous attention as a possible absorber of perovskite solar cells (PSCs). However, CsPbI₃-based PSCs have yet to achieve the high performance of the hybrid PSCs Hossain et al., [3] conducted a density functional theory (DFT) study using the Cambridge Serial Total Energy Package (CASTEP) code for the cubic CsPbI₃ absorber to compare and evaluate their structural, electronic, and optical properties. The calculated electronic band gap (Eg) using the GGA-PBE approach of CASTEP was 1.483 eV for CsPbI3 absorber. Optical properties were computed to investigated the optical properties response of CsPbI₃, using the SCAPS-1D solar cell simulation software. Among 96 device structures, the best-optimized device structure, was identified, it exhibited an efficiency of 17.9%. The effect of the absorber and ETM thickness, series resistance, shunt resistance, and operating temperature was also evaluated for the six best devices along with their corresponding generation rate, recombination rate, capacitance−voltage, current density−voltage, and quantum efficiency characteristics, and the obtained results from SCAPS-1D were compared with wxAMPS simulation results [3].

DFT methods were also used to investigate the structural, mechanical, and elastic properties, as well as electronic, optical, thermodynamic, phonon, and thermoelectric characters of the synthesized quadruple cubic perovskites CaPd₃Ti₄O₁₂ and CaPd₃Ti₄O₁₂, the calculated structural parameters of these perovskites logically corroborate the reported experimental data that clarify the authenticity of the present computations [4].

The computed band structure exhibits its metallic characteristics which are confirmed by the band overlapping in the diagram. A band of DOS is formed for the strong hybridization of the constituent elements where the O-2p orbital electrons contribute most dominantly at EF in contrast to all orbital electrons. The orbital electrons at the EF are seen maximum from both the partial density of states and charge density mapping. The electronic band structure and the density of states (DOS) are the spectra that show the variation of the energy eigenvalues with wave vectors in k- space of a crystal system that contains information about both the bonding interaction within molecules (intra-molecular) and the intermolecular interactions [5].

Bencherif et al. [6] used a combined optical and electrical approach to investigate an optimized design of a new halide (FAPbI₃)1- x(CsSnI₃)x perovskites solar cell. The transfer matrix method is used to compute the structure’s optical parameters introduced into the SCAPS-1D Simulator... The study reported that the choosing of a suitable (FAPbI₃)1- x(CsSnI₃)x alloy and optimizing the band offsets alignment, are beneficial techniques to mitigate both low absorption and unwanted effect of interfacial recombination. The results reveal that a power conversion efficiency (PCE) of 21.43% may be attained with improved CTLs and absorber characteristics [6].

In the study conducted by Rahman et al. [7], a unique alternative technique was presented by using FeSi₂ as a secondary absorber layer and In2S3 as the window layer to improve photovoltaic performance parameters, simulated on SCAPS-1D. The proposed double-absorber (Cu/FTO/In₂S₃/CdTe/FeSi₂/Ni) structure is examined and analyzed. The window layer thickness, acceptor density (NA), donor density (ND), defect density (Nt), absorber layer thickness, series resistance (RS), and shunt resistance (Rsh) were simulated to optimize the proposed configuration. When CdTe isused as a single absorber, the achieved efficieny was 13.26%. However, when CdTe and FeSi₂ used as a dual absorber, the efficiency enhanced to a value of 27.35%, the other parameters also improved to a values of 83.68% for the fill factor, 0.6566 V for the the open-circuit voltage (Voc) and 49.78 mA/cm² for the short circuit current density (Jsc). Furthermore, the proposed model well performed at 300 K operating temperature. More addition of the FeSi₂ layer to the cell structure has resulted in a significant quantum efficiency enhancement because of the rise in solar spectrum absorption at longer wavelengths (λ) [7].

In another study for Bencherif et al., [8], the authors investigated numerically an optimized design of (FAPbI₃)1-x(MAPbBr₃)x perovskite solar cell using a SCAPS-1D software package, as well as they investigated a variety of potential charge transport materials. The impact of the electronic properties of both ZnO/perovskite and Perovskite/Cu₂O interfaces on the solar cell performance were thoroughly investigated by (REF). The study found that the appropriate values of the conduction band offset as (CBO+ = 0.29) and valence band offset as (VBO+ = 0.09) assure a “spike-type” band alignment at both interfaces, this choice lowers the unwanted interfacial recombination mechanism and resulting in a challenging PCE. Furthermore, the impact of the work function of back contact were also investigated. According to simulation findings, Ni back electrodes with a work function of 5.04 eV is appropriate for Zn_0.8Mg_0.2O/(FAPbI₃)0.85(MAPbB₃)0.15/Cu2O perovskite solar cell. The optimized FTO/MgZnO/(FAPbI₃)0.85(MAPbBr₃)0.15/Cu2O/Ni PSC reached a conversion efficiency as high as 25.86%. The authors reported that the findings will pave the way for the design of low-cost, high-efficiency solar cells [8].

Lead perovskite halide shows the highest solar energy conversion efficiency at 23%. It however suffers from toxicity issues. Lead-free perovskites have been shown as a viable candidate for potential use as light harvesters to ensure renewable PV technologies, where the lead can be replaced with Sn, Ge, Bi, Sb, and Cu. The candidates reported efficiencies of up to 9%, however, their efficiency and stability in the air are still urgently needed to be enhanced. A comprehensive review of potential alternatives to lead-free perovskites shows distinctive features such as power gaps and optical absorption, as well as photoelectric parameters such as open circuit voltage (Voc), fill factor, short circuit current density (Jsc), and device architecture for its efficiency with work on the SCAPS-1D program. The results are impressive as the system parameters are constantly changing and better results are achieved. To date, researchers have made efforts in contributing to the development of perovskite semiconducting materials which have led to the rise of low cost and high efficiency concerning the simulation of the solar cell capacitance simulator-one dimension (SCAPS). In 2016, research on the device simulation of lead-free CH₃NH₃SnI₃ perovskite solar cells with high efficiency was presented [9]. Results have shown that the solar cell performance can be improved to some extent by adjusting the doping concentration of the perovskite absorption layer and the electron affinity of the buffer and HTM, while the reduction of the defect density of the perovskite absorption layer significantly improves the cell performance. By further optimizing, they obtained results of the PCE to be 23.36%, Jsc of 31.59 mA/cm², Voc of 0.92 V, and FF of 79.99%. In 2017, high stability and reproducibility were reported by Seok et al. [10], who introduced an approach to reduce defects in perovskite layers by an intramolecular exchange process, which is favorable in reducing the concentration of obvious defects and obtained an efficiency of more than 22%.

Tin-based perovskite solar cells are commonly utilized for planar interference architecture [10] and [11]. Since tin-based perovskite solar cells are affected by the oxidation process they tend not to be stable in the surrounding atmosphere. Hence, the measured efficiency of the perovskite solar cells decreases drastically with time. Researchers attempted to solve this issue by adding SnF² to the perovskite structure. For instance, a simulated work employing CuI as a hole transfer material (HTM), TiO₂ as an electron transfer material (ETM), and CH3NH3SnI3, used as absorbent materials revealed a power conversion efficiency of 24.3%. In 2018, a comparative study of different ETMs in Perovskite solar cell with inorganic copper iodide as HTM was carried out indicating lead-based perovskite solar cell (CH₃NH₃PbI₃ PSC) with CuI as HTM, TCO, IDL and different ETMs (TiO2, CdS, ZnSe, ZnO) are studied by SCAPS Simulation. Results showed that CuI as an alternate HTM has the potential to be used with a perovskite absorber and can replace the Spiro-OMETAD which is expensive and suffers from degradation. The highest PCE achieved is 23.47%. The thickness of the layers has a great influence on the performance parameters of the solar cells. Cadmium sulfide (CdS) may be a good alternative when used with CH₃ NH₃ SnI₃ absorber and cuprous oxide (Cu₂O) hole transporting material.

In this work, we have simulated a CH₃NH₃PbI₃-xClx-based perovskite device to analyze its performance as a solar cell and photodetector using SCAPS (Solar Cell Capacitance Simulator) software. SCAPS is 1-dimensional simulation software that calculates energy bands, current-voltage characteristics, and spectral response (Quantum Efficiency) by solving continuity equations for electron and hole and Poisson’s equation. SCAPS has been extensively used for the simulation of CIGS and CdTe solar cells and the results are in good agreement with experimental results [12,13,14]. In the last few years, many works of SCAPS simulation of perovskite solar cells have been reported [15,16,17]. Since the exactions in the perovskite material are of Wannier-type with the binding energy of 50 meV, we can deal with their photo-excited carriers in the same way as in the case of inorganic materials like CIGS and CdTe [18,19].

The main objectives of this research is to develop a perovskite, clean, and environmentally friendly perovskite solar cell, to determine the effective material that can replace the lead perovskite solar cells, using computer software tools (SCAPS). The novelty in this study is the use of more than HTM (CuO2, CuI, NiO, PEDOT: PSS) with different paramount terms, and moreover, the use of Germanium and Tin as lead substitutes. Most of the parameters were taken from the references, however, the adjustment of those parameters was an objective in this study as the four used variables were diverse in terms of their stability, price, and availability. Furthermore, was in employing the non-ideal conditions in the simulation phase and approximating them to the reported experimental works’ outcomes have been conducted in this study.

2. Materials and Methods

In this section the method of simulating a proposed perovskite as a solar cell will be presented, along with the operating principle of the perovskite solar cell. The proposed perovskite solar cells simulation is carried out with the help of SCAPS software [12]. SCAPS has been well adapted for modeling many micros, thin and polycrystalline devices, and photonic structures [20,21,22]. Accordingly, SCAPS-1D can be used to simulate the architectures of perovskite solar cells. From the literature, the experimental results coincide with those of a SCAPS-1D simulation for the design and development of a highly efficient Tin Halide Perovskite solar cell. The SCAPS-1D has several advantages over the other simulation software, since it can grade almost all parameters of semiconductor layers.

2.1. The Architecture of the Device

The perovskite solar cell based on lead, germanium, and tin differs in a homogeneous and symmetric inverted planar structure. In this type of architecture, three layers were placed between the two electrode materials. CH₃NH₃PbI₃, CH₃NH₃GeI₃ and CH₃NH₃SnI₃ are used as the absorber layer. HTMs such as CuO₂, CuI, NiO, PEDOT: PSS were investigated and TiO₂ was selected as the electron transport material (ETM), the back contact and front contact of the cell structure is shown in Figure 1.

2.2. Simulated Parameters

The parameters for this study are selected from previous studies and experimental works as shown in

Table 1. The parameters utilized in the simulation process, [23,24,25,26,27,28].

Parameters	FTO	TiO	CH3NH3GeI3	CH3NH3PbI3	CH3NH3SnI3	NiO	CUI	PEDOT:PASS	Cu2O
Thickness (μm)	0.3	0.100	0.05	0.5	0.5	0.100	0.100	200	0.100
Bandgap Eg(eV)	3.5	3.25	1.9	1.55	1.3	3.8	3.100	1.5	2.170
Electron affinity (eV)	4	4	3.98	4.200	4.170	1.6	2.3	3.75	3.100
Relative dielectric permittivity (Er)	9	10	10	6.5	6.5	10	6.5	10	7
Effective conduction band density, Nc (cm−3)	2.2 × 1018	2.2 × 1018	2.2 × 1016	2.2 × 1019	2.2 × 1019	2.8 × 1019	2.2 × 1019	1 × 1021	2.2 × 1019
Effective valence band density, Nv (cm−3)	2.2 × 1019	1.1 × 1019	2.2 × 1015	2.2 × 1019	2.2 × 1019	1 × 1019	1.8 × 1019	1 × 1021	2.2 × 1019
Electron mobility, μn (cm2v−1s−1)	20	100	1.620 × 103	2.000 × 101	1.600 × 100	1.200 × 101	1.000 × 102	1 × 100	80
Hole mobility, μp (cm2v−1s−1)	10	25	1.01 × 103	1.000 × 101	1.600 × 100	2.800 × 101	4.390 × 101	4 × 101	80
Donor concentration, ND (cm−3)	1 × 1019	1 × 1019	9	0	0	0	0	0	0
Acceptor concentration, NA (cm−3)	0	0	9	1 × 1015	3.2 × 1015	1 × 1019	1 × 1019	1 × 1019	1 × 1018
Capture cross section electrons (cm²)	1 × 10-15	1 × 10-14	2 × 10-15	2 × 10-15	2 × 10-15	2 × 10-15	2 × 10-15	1 × 10-15	1 × 10-15
Capture cross section holes (cm²)	1 × 10-15	1 × 10-14	2 × 10-15	2 × 10-15	2 × 10-15	2 × 10-14	2 × 10-14	1 × 10-15	1 × 10-15
Energy level with respect to Reference (eV)	0.600	0.600	0.650	0.650	0.650	0.600	0.600	0.600	0.650
Defect density, Nt (cm−3)	1 × 1016	1 × 1016	1 × 1013	1 × 1013	1 × 1013	1 × 1014	1 × 1014	1 × 1016	1 × 1016

. The thermal velocities of the holes and the electron are taken in the range of 10⁷ cm/sec. From the previous studies, the value of the receiver density is taken as 3.2 × 10¹⁵ l/cm³, and the value of the radiative recombination coefficient is taken as 3 × 10⁻¹¹ cm³/s. Furthermore, Hole and Electron thermal velocity (cm/s) were set at 1 × 10⁷, Defect type was set to neutral, Energetic distribution was set to Gauβ, Reference for defect energy level Et was set to above Ev and Characteristic energy (eV) was set to 0.1.

3. Results

Performance of Optimized Parameters

Thickness, electrons affinity of ET, HTM, and the doping concentration are among the factors that affect PCE, FF, V_oc, and J_sc, and the final and improved parameters are presented with better performance for each of the perovskites depending on Pb, Ge, and Sn as shown in the

Table 2. Optimum parameters of the perovskite solar cell device (CH₃NH₃PbI₃).

Optimized Parameters	ETM (TiO)	Absorber (CH3NH3 PbI3)	HTM (CuO2)
Thickness (μm)	-	0.9
Electron affinity (eV)	3.8		3.2
Doping concentration, NA (cm−3)		1 × 1014

,

Table 3. Optimum parameters of the perovskite solar cell device (CH₃NH₃GeI₃).

Optimized Parameters	ETM (TiO)	Absorber (CH3NH3GeI3)	HTM (CuO2)
Thickness (μm)	-	0.9
Electron affinity (eV)	3.70		3.03
Doping concentration, NA (cm−3)		1 × 109

,

Table 4. Optimum parameters of the perovskite solar cell device (CH₃NH₃SnI₃).

Optimized Parameters	ETM (TiO)	Absorber (CH3NH3SnI3)	HTM (CuO2)
Thickness (μm)	-	0.8
Electron affinity (eV)	3.75		3.3
Doping concentration, NA (cm−3)		1 × 1015

,

Table 5. Optimum performances of solar cells with different HTM layers (CH₃NH₃PbI₃).

HTM Materials	Voc (V)	Jsc (mA/cm2)	FF (%)	PCE (%)
CuO2	1.16	25	62.71	18.28
CuI	0.8	25	81	16.42
NiO	0.7	24.99	81.21	15.37
PEDOT:PASS	0.6	24.95	78.21	11.86

,

Table 6. Optimum performances of solar cells with different HTM layers (CH₃NH₃GeI₃).

HTM Materials	Voc (V)	Jsc (mA/cm2)	FF (%)	PCE (%)
CuO2	0.91	15.91	78.06	11.52
CuI	0.99	15.78	72.21	11.30
NiO	0.80	15.91	85.83	10.97
PEDOT:PASS	0.65	15.91	83.70	8.68

and

Table 7. Optimum performances of solar cells with different HTM layers (CH₃NH₃SnI₃).

HTM Materials	Voc (V)	Jsc (mA/cm2)	FF (%)	PCE (%)
CuO2	0.99	34	71.30	24.54
CuI	0.91	34	75.84	23.71
NiO	0.85	33	78.45	22.66
PEDOT:PASS	0.70	32	78.65	18.34

and Figure 2, Figure 3 and Figure 4.

4. Discussions

4.1. The Influences of the Thickness

The influences of the thickness of the absorbent material to confirm the optimum thickness of the absorbent layer, the simulations were performed for lead CH₃NH₃PbI₃ from the range of 0.05 μm to 2 μm, with the optimal range being in the range of 0.9 μm. As with germanium CH₃NH₃GeI₃, the range was from 0.6 μm to 1.5μm, and the best range was found also 0.9 μm, and then the last substitute for tin CH₃NH₃SnI₃ from the range of 0.5 μm to 1.5 μm founded the better range was 0.8 μm. Thus, it can be said that an increase in the thickness of the absorbent layer means an increase in the absorption of light, and that may lead to an increase in the efficiency and current, however, it also can decrease the fill factor, which can improve the efficiency while increasing the voltage.

Figure 5, Figure 6 and Figure 7 revels that an increase in thickness of the absorber layer means we are increasing the light absorbed which could result in an increase in PCE. The maximum PCE of Pb, Ge, and Sn respectively 18.28%, with J_sc of 25.00 mA/cm², FF of 62.71%, V_oc of 1.16 V is achieved when the thickness reaches 0.9 μm in Pb, PCE of 11.52%, with J_sc of 15.92 mA/cm², FF of 78.06%, V_oc of 0.92 V is achieved when the thickness reaches 0.9 μm in GE and the last PCE of 24.54%, with J_sc of 34.45 mA/cm², FF of 71.30%, V_oc of 0.99 V is achieved when the thickness reaches 0.8 μm.

4.2. Influence of Electron Affinity ETM

The electron affinity in Tio₂ ranges from 3.60 to 4.60 volts. The critical displacement between the ETM and the absorbent layers can also be adjusted, which is the band displacement as shown in Figure 8, Figure 9 and Figure 10. The variation of electron affinity with the solar cell parameters results in to decrease in FF, PCE, J_sc, and V_oc, due to the proper selection.

The simulation results clearly showed that with high or low values of electron affinity, it is desirable to align the boundary energy levels, and thus the efficiency of perovskite could be improved. By treating Ev of the HTM for the perovskite layer, the electron affinity observed for CuO₂ had an effect. In order to obtain the optimal values of the electronic affinity for CuO₂ different parameters were chosen and the affinity varied from 3.60 V to 4.60 V volts as shown in the figures. The values of V and FF were improved significantly and correspondingly, the level of efficiency has been enhanced.

4.3. Influence of Electron Affinity HTM

The electron affinity in CuO₂, CuOI, NiO, and PEDOT: PASS respectively range from 2.70 to 3.30 volts. The critical displacement between the HTM absorbent layers can also be adjusted, which is band displacement. The variation of electron affinity with the solar cell parameters results in FF, PCE, J_sc, and V_oc being unstable, but Js_c changes from 2.7 eV to 3.3 eV. Due to the proper selection can get good results as shown in Figure 11, Figure 12 and Figure 13.

In order to better determine HTM the efficiency of PSCs the parameters were simulated with HTMS different such as CuO₂, CuOI, NiO, and PEDOT: PASS respectively parameters ETM and the perovskite layers were originally and accurately codified. In addition to that, the values were used for the mass and image distortion densities to maintain a balanced analysis with an abundance of correctness that shows the shapes. The characteristic curves of the voltage V and the efficiency PEC that have been simulated. It leads and supports the good performance of PSC based on CuO₂ alignment of boundary energy levels and appropriate electron affinity and hole mobility for the materials used.

All lead-free, inorganic lead-free perovskites are encouraging and gentle materials in solar energy harvesting applications. The performance of optimized parameters Thickness, electrons affinity of ET, HTM, and the doping concentration are among the factors that affect PCE, FF, V_oc, and J_sc, and the final and improved parameters are presented with better performance for each of the perovskites depending on Pb, Ge, and Sn. This paper presents a numerical investigation of a confined mode arrangement (FTO/TiO₂/CH₃NH₃PbI₃/CH₃NH₃GeI₃/CH₃NH₃SnI₃/CuO₂) of heterogeneous perovskite-based solar cells, (CH₃NH₃PbI₃/CH₃NH₃GeI₃/CH₃NH₃SnI₃) using SCAPS-1D.

This scientific paper aims to enhance knowledge and explore the effect of the hole transport materials (HTM) and the electron transport materials TiO₂ (ETM) on the performance of the proposed cell and based on the assumptions of the parameters with high accuracy from the experiment on the device itself and its tuning and previous studies. Also, the concentration of vectors for the absorption layer was studied and the effects of efficiency were studied, which led to the best performance to obtain the following results CH₃NH₃SnI₃, the best results showed an overall efficiency of 24.54%, FF of 71.30%, J_sc of 34 mA/cm², and V_oc of 0.99 V. Lead-free Perovskite solar cells.

4.4. Influence of the Doping Concentration

The influence of the doping concentration is very important when the doping concentration differs from the absorbent layer with respect to lead at range 1 × 10¹³ to 1 × 10¹⁵ shown in Figure 14, Tin at range 3.2 × 10¹³ to 3.2 × 10¹⁶, Figure 15 and Germanium only is the same acceptor and donor at 1 × 10⁹ and the increase of the effect decreases the FF and increases the PCE due to the invented electric field and also the fermi energy is withdrawn into energy. Parity is where we get more holes but much fewer electrons.

Tin is a non-toxic and accessible material that has enormous capabilities and potential to be used in the future of lead-free solar cells.

The doping and the thickness of the bands were studied on the conversion efficiency of the different perovskite cells. The results indicate that the excellent performance of the device is guaranteed by the following values in its layer CH₃NH₃PbI₃ as it found the absorption thickness 0.9 μm ideal, electronic band, 3.8 eV, and doping concentration 1 × 10¹⁴ NA (cm⁻³)

As in class CH₃NH₃GeI₃ as it found an absorption thickness of 0.9 μm ideal, an electronic band of 3.70 eV, and a doping concentration of 1 × 10⁹ NA (cm⁻³) also the best in the tin layer CH₃NH₃SnI₃ as it found an absorption thickness of 0.8 μm ideal, electronic band, 3.75 eV and doping concentration 1 × 10¹⁵ NA (cm⁻³), where the highest efficiency is achieved by 24.54% after optimizing and checking the various parameters, as the simulation results provide beautiful work, useful insights, and guidance for an excellent design.

In addition to that, to improve the basic properties of each of the active layers, and then examine the effect of parameters, including thickness and doping density, in terms of performance, efficiency, and recombination and construction schemes, after improving all the mentioned properties, as the efficiency was developed by about 18.28% in CH₃NH₃PbI₃,11.52% in CH₃NH₃GeI₃ and 24.54% in CH₃NH₃SnI_3.

The efficiencies of our reported perovskite material with many previously published papers (

Table 8. Comparison between different perovskite parameters with the current study.

Perovskite Layer	ETM	HTM	Jsc mA/cm2	Voc (v)	FF %	PEC%	Ref
MAPbI2Br	TiO2	CuO2	23.30	1.29	83.6%	25.21 %	[2]
CH3NH3SnI3	SnO2	Spiro-OMeTAD	31.3	1.24	84.8%	33.2 %	[29]
CH3NH3SnI3	Zn2SnO4	Spiro-OMeTAD	32.30	1.185	64%	24.3 %	[30]
FA-xCsxSnI3	TiO2	CuO2	31.4	0,89	76.7%	22 %
CH3NH3SnI3	TiO2	Spiro-OMeTAD	32.76	0.82	74 %	20.08%	[30]
CH3NH3SnI3	TiO2	CuO2	34	0.99	71.30	24.54%	This work

) found that our reported perovskite material displayed significantly better performance in terms of hole transport material (HTM), circuit current density (J_sc mA/cm²), electron transport material (ETM), voltage (V_oc (v)), fil factor (FF%) and efficiency (PEC%).

5. Conclusions

This study presents an in-depth analysis and insight into ways to improve and enhance the efficiency of lead free perovskites, based on tin and germanium.. The placement of lead is damaging to the environment despite its stability and ease of application. Adjusting the simulation process to study the perovskite cells according to standards and by means of which the thickness of the absorbent layer is selected, and the parameters and electron affinity for each of HTM, ETM are selected. Moreover, the doping concentration for the absorbed layer using SCAPS-1D to obtain different results and different contrast using HTM for each CuO₂, CuI, NiO and PEDOT: PASS. We were able to obtain and verify the highest efficiency, between the comparisons after improving the performance of tin is J_sc = 34.45 mA/cm², V_oc = 0.99 V, FF = 71.30% and PCE = 24.54% and lead is J_sc = 25.00 mA/cm², V_oc = 1.16 V, FF = 62.71% and PCE = 18.28% and finally germanium is J_sc = 15.91 mA/cm², V_oc = 0.92 V, FF = 78.06% and PCE = 11.52%. Finally, the efficiency of these cells appears with different variations in lead, tin and germanium after optimization. The proposed structure needs to be verified through physical manufacturing and testing.