Designing an efficient lead-free perovskite solar cell with green-synthesized CuCrO₂ and CeO₂ as carrier transport materials

Abstract

With increased efficiency, simplicity in manufacturing, adaptability, and flexibility, solar cells constructed from organic metal halide perovskite (PVK) have recently attained great eminence. Lead, a poisonous substance, present in a conventional PVK impacts the environment and prevents commercialization. To deal with this issue, a number of toxicity-free PVK-constructed solar cells have been suggested. Nevertheless, inherent losses mean the efficiency conversion accomplished from these devices is inadequate. Therefore, a thorough theoretical investigation is indispensable for comprehending the losses to improve efficiency. The findings of a unique modelling method for organic lead-free solar cells, namely methylammonium tin iodide (MASnI₃), are investigated to reach the maximum practical efficiencies. The layer pertinent to MASnI₃ was constructed as a sandwich between a bio-synthesized electron transport layer (ETL) of CeO₂ and a hole transport layer (HTL) of CuCrO₂ in the designed perovskite solar cells (PSCs). In this study, the use of algae-synthesized Au in the back contacts has been proposed. To obtain the maximum performance, the devices are further analyzed and optimized for active layer thickness, working temperature, total and interface defect density analysis, impedance analysis (Z′–Z), and capacitance–voltage (C–V), respectively. An optimal conversion efficiency of 26.60% has been attained for an MASnI₃-constructed PSC. The study findings may open the door to a lead-free PSC through improved conversion efficiencies.

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1. Introduction

The primary research goal for the decade is the overall augmentation of power conversion efficiency (PCE) of non-toxic, renewable solar cells, as a replacement for conventional fuels. Perovskite solar cells (PSCs) in particular have attracted great interest because of their remarkable qualities, including their extremely high coefficient of absorption, low cost, long charge diffusion length, great electron mobility, low trap state density, low binding energy of excitons, and configurable band gaps.^1–5

A perovskite material has an archetypical structure relating to ABX₃, where A is likely to be a methylammonium cation (CH₃NH₃⁺). A has a very small ionic radius of ∼0.18 nm. B is often Pb or Sn, while X is characteristically a halide.^6–8 It should be mentioned that Kojima et al. introduced a noble PSC structure, where CH₃NH₃PbX₃ and Br were used to build the active layer as a halide material, which presented a recorded PCE of up to 3.8%.⁹ Thenceforth, remarkable progress have been achieved in PSC performance over recent years, but there is still a lot of room for improvement. Suitable material selection with optimum thickness, defectivity, and adequate working temperature in device architectures is critical in improving device effectiveness.

A PSC sustains a lower photocurrent density because of a characteristically thin active layer absorbing markedly low quantities of photons. Interestingly, as the thickness of the perovskite active layer increases, less charge extraction is observed in the device output. Also, reasonable recombination-related loss is observed with increased active layer thickness.^8,10 So, selecting a suitable thickness becomes a primary concern amongst others in PSC devices.

Apart from the instability involved, the influence of electrode degradation on perovskite solar cells has also been studied.¹¹ Their stability with Au and Ag as the electrodes in a triple-cation MAPbI₃-based PSC were also tested.¹² In another study, it can be seen that the degradation of a lead halide PSC was greatly influenced by the hole transport layer and the effect of the metal electrode interfaces was also revealed.¹³ So, stability based on the electrodes in the PSC design has been studied thoroughly in the reports discussions above.

The perovskite layer is held in a sandwich between the electron (ETL) and hole carrier transport layers (CTLs) in classic PSC architecture (ETL and HTL). Spiro-OMeTAD was used in HTL to maximize effectiveness and stability.¹⁴ Concurrently, Liu et al. improved the efficiency of a complex device structure, with an ITO/TiO₂/CH₃NH₃PbI_3−xCl_x/Spiro-OMeTAD/Ag layer structure, by 15.4% by employing contemporary vapour deposition approaches.¹⁵ But, due to cost, the Spiro-OMeTAD application is impractical to use, a significant concern in PSC manufacturing.⁸ To replace this complex structure, we employ similar characteristics of the HTL material CuCrO₂ for application in PSC devices. Similarly, TiO₂ offers relatively low impacts on charge transportation to the anode; it has a non-matching bandgap with the active layer. Moreover, a green-synthesis approach makes the material economical for perovskite fabrication. Recently, efficiency with reference to a PSC was increased by using CeO₂ as an ETL and an annealing treatment, increasing efficiency up to 18.36%.¹⁶ Butt et al., synthesized CeO₂ nanoparticles (NPs), from petals, a plausible material for ETL in present devices. It is important to highlight that planar heterojunction PSCs are workable substitutes for mesoscopic designs because of their simplicity and ease of production.^17,18

Applications of ‘green-synthesized nanomaterials’ from microbes (algae/bacteria//actinomycetes/fungi) and plants in modern science and technology have come to the fore thanks to their sustainability, cost-effectiveness, and low toxicity, together with their eco-friendly properties. United Nations ‘Sustainable development Goal’-7 is directly related to affordability together with clean energy. Applying green-synthesized materials in solar cells with the required photovoltaic parameters will provide clean energy with greater efficiency and affordable cost, achieve economic growth, and alleviate climate change.

The ‘CeO₂-NPs’ were prepared from the flowers of Cassia glauca.¹⁹ The dried petals (20 g) of the flowers were extracted in dH₂O (200 mL) and filtered. The extract (100 mL) was pre-heated (75 °C) with stirring (1000 rpm). The extract was alkylated [pH 9; NaOH (0.1 M)]. Ce(NO₃)₃·6H₂O (5 g) was added to the extract, heated (75 ± 5 °C), stirred (1000 rpm), and finally centrifuged to collect the NPs. The CeO₂-NPs were spherical, presenting a lattice constant of 5.42 Å, and a ‘crystallite size’ of 3.20 nm. The delafossite (CuCrO₂) was prepared from chelating/complexing Aloe vera extracts,²⁰ where 15 g of dried plant in 100 mL of dH₂O was stirred for 1 h (60 °C). Millimole equivalents of both Cu(NO₃)₂·3H₂O (0.241 g) and Cr(NO₃)₃·9H₂O (0.40 g) were separately added to 100 mL of extract, mixed, and heated (80 °C) until a clear solution appeared. The solution was further heated (100–120 °C) to a gelatinous mass, dried completely (150 °C, 12 h), and calcined (500 °C, 6 h).

‘Au-NPs’ were synthesized from Prasiola crispa, an epilithic alga, by bioreduction.²¹ Briefly, 1 g of dry powder of the alga in HAuCl₄ solution (10⁻³ M, 100 mL) was stirred until the colour changed to purple (12 h). The NPs presented an approximately spherical shape (5–25 nm), a crystallite size of 9.8 nm, lattice fringes of 0.233 nm, and polycrystalline nature. A ‘dynamic light scattering’ study revealed the average diameter to be 10 ± 8.6 nm.

A significant advancement in Pb-based PVK materials has occurred in the last few decades. However, the toxicity of lead remains a primary barrier to the broad adoption of PSCs.²² These issues can be overcome by substituting Sn for Pb, which is toxic-free in nature.^23–25 Moreover, MASnI₃ material has certain advantages pertaining to its bandgap (∼1.3 eV), which is remarkably smaller than that of a conventional PVK material.²⁶ Its reduced bandgap might be the reason for photon absorption by MASnI₃ over a wide spectrum of wavelengths. A wider photon wavelength absorption and narrower bandgap enhance device efficiency (from 1.3 eV). The optimization of defect-less, light-harvesting layers to obtain desired optoelectronic characteristics has more impact on the output of a PSC device.

In the present work, SCAPS-1D, a (1-dimensional) simulator of solar cell capacitance, developed by ELIS, University of Ghent, Belgium was used for investigation of the associated PSC, developed with a drift-diffusion model.²⁷ The advantages of the simulator include a deposition capability pertaining to a maximum of seven semiconducting layers together with the ability to rank virtually all characteristics. The mechanism involves the solving of the Poisson equation besides continuity equations, and the simulations may be done under both dark and light conditions.²⁸ The above-mentioned simulator is also convenient for analysing various models with recombination mechanisms, batch computation with the bulk, and interface defect-level calculation.²⁹ The current simulation is applied to both crystalline and amorphous solar cells.³⁰ The present work applies AM1.5G solar irradiance relating to an analysis of carrier transport processes and electrical outputs for the construction of an optical profile, which could be converted into an electrical model for MASnI₃-based PSCs.

2. Simulated device structures

As an innovative approach to the advancement of the device, we propose the previous work by Sarkar et al. to find the HTL of CuCrO₂ and CeO₂ as the ETL as reported by Butt et al. (see Fig. 1(i–iii)).^19,20 Similarly, the algae-synthesised Au is used as a back contact for the PSC, as shown below. We designed the structure of ITO/CeO₂/MASnI₃/CuCrO₂/Au (Fig. 2(i)). The green-synthesized ETL and HTL were implemented in a PSC device, as shown in Fig. 2. The ITO top electrode (0.1 μm) is followed by a CeO₂ layer (0.1 μm) in the simulated PSC devices, which is a green-synthesized ETL (Fig. 1). In the architecture of the PSC, the electrons produced are effectively collected from the absorber layers. The absorber layer of the device has a thickness of 0.6 μm and is preserved between an ETL and the HTL. The cathode efficiently receives a hole from PVK thanks to the hopping mechanism. CuCrO₂ with a thickness of 0.1 μm was also green-synthesized (Table 1). The designed layers were initially as depicted in Table 1. Using the ETL (CeO₂) and HTL (CuCrO₂) results in better alignment with the perovskite material. Apart from the band alignment, both bio-synthesised materials have suitable carrier mobility. The cathode is made of Au, an algae-synthesized material of 0.1 μm thickness. Whereas in Fig. 2(ii), the absorption coefficient of the MASnI₃ material is depicted from SCAPS-1D. The modelling-related attributes in PSC devices are listed in detail in Table 1.

Fig. 1 The green-synthesized (i) CuCrO₂ morphology for use as HTL (from Aloe barbadensis);³³ (ii) the morphology of CeO₂ (from petals of Cassia glauca) (reprinted with permission from ref. 19). (iii) Au-nanoparticle (from Prasiola crispa) as a back contact of the MASnI₃-based PSC devices (reprinted with permission from ref. 21).

Fig. 2 (i) Simulated architecture of MASnI₃-based PSC devices, and (ii) absorption coefficient of MASnI₃ material under AM1.5G illuminance.

Table 1 The simulated inputs in the architecture of the PSC device^20,31,32

Parameters	Terms	ETL (CeO2)	PVK (MASnI3)	HTL (CuCrO2)
d (μm)	Thickness	0.1–0.15	0.1–0.9	0.1–0.15
Eg (eV)	Bandgap	3.2	1.3	3.0
εr	Relative permittivity	9	8.2	9.5
χ (eV)	Electron affinity	4.4	4.1	2.1
Nc (cm^−3)	Effective DoS at CB	1 × 10^20	2 × 10^18	1 × 10^19
Nv (cm^−3)	Effective DoS at VB	2 × 10^21	2 × 10^18	1 × 10^19
μn (cm^2 V^−1 s^−1)	Mob. of electrons	100	1.6	0.1
μp (cm^2 V^−1 s^−1)	Mob. of holes	25	1.6	2.53
Da (cm^−3)	Dop. conc. of the acceptor	0	0	6.4 × 10^15
Dd (cm^−3)	Dop. conc. of donor	1 × 10^21	1 × 10^19	0
Nt (cm^−3)	Defect density	1 × 10^14	1 × 10^14	1 × 10^14

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3. Mathematical modeling

The Solar Cell Capacitance Simulator, SCAPS-1D, allows for numerical modelling of the key parameters influencing the output of a PSC device.²⁷ Considering steady-state conditions, the semiconductor materials are governed by a one-dimensional equation. The charge density of the p–n junction, and its relationship with the electric field (E), can be depicted using the following symbols:Here φ is electrostatic potential; q is charge; ε_s is static relative permittivity for the medium; n and p are electron and hole, respectively; N_D and N_A are donor and acceptor densities; and N_def is defect density for the acceptor and donor.

In the PSC device, the equation for carrier continuity was followed:³⁴

where j_p and j_n are the current densities of the hole and electron; G is the carrier generation rate; and U_n(n, p) is the recombination rate pertinent to the electron and hole.

Simultaneously, the carrier current density was ascertained from the equations:³⁵

Here q is charge; μ_p and μ_n are carrier mobilities; and D_p D_n are the diffusion coefficients of the carriers.

The basic equation pertaining to solar cells (current density, generation and recombination rate) was extracted from the SCAPS-1D software.

4. Results and discussion

An extensive examination together with an analysis pertaining to intrinsic solar cell parameters is presented in subsections 4.1 to 4.9.

4.1 Alignment of the bandgaps of the PSC structure

The band diagram encompassing the simulated device (PSC) at equilibrium is presented in Fig. 3 to understand the carrier dynamics within the device. The first MASnI₃-constructed PSC device presents an energy barrier (0.02 eV) between the TiO₂ conduction band minimum (E_C) and the lowest unoccupied molecular orbital (LUMO) in the absorber material with an offset of around 1.85 eV between the HOMO and HTL. For an MASnI₃-constructed PSC, rapid electron transport can be shown; see below. The details are depicted in Fig. 3 with ETL, HTL, and perovskite thickness.

Fig. 3 The energy band diagrams ascribed to an MASnI₃-based PSC device with designed ETL and HTL.

4.2 The impact of active layer thickness, ETL and HTL on PSC output

A predetermined extension applying to the preconditioned input parameters at 300 K was applied to complete the thorough simulation analysis (Table 1). Further, to understand the performance of the device with variation in absorber layer thickness, the PV parameters were obtained and are reported in Fig. 4. The effect associated with active layer thickness with reference to the output attributes of the MASnI₃-based PSCs has been confirmed in Fig. 4. As the thickness of the perovskite absorbing layer (PAL) in the device grows, the short circuit current density (J_SC), open circuit voltage (V_OC), and power conversion efficiency (PCE%) rise to achieve a saturated value (31.31 mA cm⁻²) at 0.9 μm (Fig. 4). It should be highlighted that a rise in the generation rate of excitons occurred with greater absorbance in the absorber layers with PAL thickness of 0.9 μm. Additionally, the FF of the device falls monotonically as the thickness increases because a small increase in thickness increases carrier recombination.

Fig. 4 The effect of the thickness of the MASnI₃ layer on the PV parameters of the designed PSC device.

The J_SC, V_OC, FF and PCE at different thicknesses of CuCrO₂ and CeO₂ are presented in Fig. 5 and 6, respectively, to understand the impact of variation in HTL and ETL layer thickness. The parameters achieved a maximum value with thicknesses of 100 nm each of CuCrO₂ and CeO₂. Previous work by Bhattarai et al. also shows that the optimized ETL and HTL thickness is 100 nm.³⁶ It achieves larger values for J_SC (31.31 mA cm⁻²), V_OC (∼1.05 V), FF (80.98%) and PCE (26.60%). This might be because of the lack of contribution to photon absorption in a PSC.²²

Fig. 5 The effect of the thickness of the CuCrO₂ layer on the PV parameters of the designed PSC device.

Fig. 6 The effect of the thickness of the CeO₂ layer on the PV parameters of the designed PSC device.

4.3 The impact of temperature on PSC parameters

A complete analysis pertaining to solar cell properties with variation in temperature is presented in Fig. 7. The four parameters, J_SC, V_OC, FF, and PCE, all drop as the temperature rises from 300 to 375 K, relating to the degradation of the materials. For the MASnI₃-based PSC devices, J_SC was a maximum at 300 K (31.31 mA cm⁻²). These values may be appropriate for the device output characteristics. Due to internal degradation of the PVK material, V_OC continues to degrade and exhibits a higher value at 300 K (1.05 at 300 K dropping to 1.034 V at 375 K). Similarly, FF value decrease from 80.5% to 79.55% as the temperature increases from 300 K to 375 K. The PCE (26.65% at 300 K) degrades to 25.9% at a temperature of 375 K.

Fig. 7 The effect of temperature on the solar cell PV output parameters in the PSC.

4.4 The impact of defect density and thickness on the parameters of the PSC

The previous subsection concerning the thickness of the fixed absorber layer with reference to the PSC device looked solely into the effects of bulk defect density on performance metrics, as reported in Fig. 8. However, varied fault concentrations at disparate thicknesses of absorber layers help us to comprehend device performance with reference to the combined variations in defect and thickness. Therefore, the collective variation is obtained in a separate subsection. Determining the impact of defect density on PSC performance as a whole is the foremost goal of a study on defect density. Initially, defect density was raised to 1 × 10¹⁶ cm⁻³ from 1 × 10¹⁴ cm⁻³ by changing the absorber layer thickness (0.1–0.9 μm). In an earlier report by Mahmoud et al. the efficiency improved with a defect density of 1 × 10¹⁴ cm⁻³.³⁷ While an experimental verification by Noel et al. also depicted the same defect density in an MASnI₃-based PSC.³⁸

Fig. 8 The contour diagrams of simulated MASnI₃-PSC under optimized conditions with illuminance of AM1.5G.

4.5 The impact of acceptor density on the PSC parameters

The acceptor defect density varied between 1 × 10¹⁴ cm⁻³ and 5 × 10¹⁷ cm⁻³ and the corresponding PV parameters were obtained, as reported in Fig. 9. The disparity in the J_SC is well observed and achieves a maximum of 31.31 mA cm⁻² at 1 × 10¹⁵ cm⁻³ and decreases to 29.8 mA cm⁻². In comparison, the V_OC and FF rise as the acceptor density increases. However, the PSC-device's relevant PCE was almost equal as the acceptor defect density varied from 1 × 10¹⁴ to 5 × 10¹⁷ cm⁻³. So, the maximum PCE of 26.60% is presented at a smaller acceptor density (Fig. 9).

Fig. 9 The impact of MASnI₃ acceptor density on the PSC under illuminance of AM1.5G.

4.6 The influence of total defect density on four output parameters of the PSC

The most dominant solar cell output metrics (J_SC, V_OC, FF, and PCE) are presented in Fig. 10 as a function of defect density appertaining to the respective perovskite materials. Primarily, the PSC characteristics decrease as the defect density intensifies. It is crucial to note that the PSCs have drastically disparate solar cell parameter values. The MASnI₃-based perovskite efficiency is 26.60% at a defect density of 1 × 10¹⁴ cm⁻³. The present result offers better outputs than the previous report by Dureja et al.³⁹ The MASnI₃-based PVK offers a high value of V_OC, i.e. almost 1.05 V. In addition, the architecture relevant to the device exhibits the same characteristics in terms of FF.

Fig. 10 The effect of MASnI₃ defect density on the PV outputs of the PSC devices.

4.7 The impact of interface defect density on the output parameters of the PSCs

The study includes an investigation of CuCrO₂/MASnI₃ interface defect density. Fig. 11(i) shows the PCE over the defect density (N_t) pertaining to this interface. The calculation is concerned with the Fermi level relating to the device (E_F). As the PCE rises at smaller values of N_t (1 × 10¹⁰ cm⁻²), the PCE is 26.60%. For further evaluation, the defect range from 1 × 10¹⁰ cm⁻² to 1 × 10¹⁵ cm⁻² was considered for further analysis. It was found that all four parameters are smaller for higher interface defect density (N_t = 1 × 10¹⁰ cm⁻²). The MASnI₃/CeO₂ interface provides valuable information about the interface defect density between the PAL and the ETL layer, as depicted in Fig. 11(ii). Numerically, the maximum value of PCE is 26.60%, drastically dropping to 17.50% at N_t = 1 × 10¹⁵ cm⁻². It is emphasized that PCE is significantly affected, attributed to the higher level of N_t near the deep defect trap state.

Fig. 11 (i and ii) The impact of both interfaces (L1 – CuCrO₂/MASnI₃ and L2 – MASnI₃/CeO₂) on the overall output of the PSC device.

4.8 The J–V characteristics of PSCs of different thicknesses, defect densities and temperatures

The J–V parameters pertaining to PSC devices for different ranges of thickness (100 nm to 900 nm), bulk defect density (1 × 10¹⁴ to 1 × 10¹⁶ cm⁻³), and temperature (300–375 K) are depicted for a simulated PSC [Fig. 12(i–iii)]. Firstly, the current density intensifies as the thickness increases to attain a saturated value of 0.9 μm [Fig. 12(i)]. This may be due to extensive higher absorption with greater thickness. In Fig. 12(ii), increasing the defects greatly impacts the voltage and lowers the voltage when it achieves a value of 0.92 V at a higher defect density value. A comparable trend was noted for raising the temperature from 300 to 375 K, as depicted in Fig. 12(iii). The higher temperature lowers the V_OC, related to the damage done to the interior material of the PSC devices.^31,40 The MASnI₃-based PSC explicitly gives 1.05 V and 1.06 V at 300 and 375 K, respectively. The shift in potential from a higher to a lower value is well observed (Fig. 12).

Fig. 12 Impact of (i) thickness, (ii) defect density, and (iii) temperature on the J–V parameter of the PSC devices.

4.9 The impedance, capacitance and EQE analysis of the optimized device

In the Nyquist curve, the X-axis represents resistance due to recombination, and the Y-axis represents the geometrical capacitance of the solar cell, indicating that the carrier accumulates at the interface layers. At high frequencies, the measured resistance resembles the recombination resistance of the material. The capacitance at high frequencies represents the geometric capacitance, signifying interface charge accumulation.⁴¹ The low-frequency response is more dubious and is related to ionic motion and hysteresis.⁴² It may turn into an inductive element due to the accumulation of ions and the reduction in extraction barriers. The study of imaginary and real impedance values can be well observed in Fig. 13. The impedance and real impedance show how reliable the device is, as a lower impedance is always preferable in PSC device manufacturing. The overall impedance value is −1.75 × 10⁵ Ohm cm² with real impedance of 32 000 Ohm cm². Comparatively, the present work matches the value reported earlier by Bhattarai et al.⁴³

Fig. 13 Nyquist curve for the impedance analysis in the designed PSC device after all-round optimization techniques.

A capacitance analysis for the PSC device provides an important outlook on the designed device. It can be seen that the highest capacitance value is attained at a minimal level of defect density. The CF plot demonstrates that when the frequency surpasses 1 MHz, the capacitance reduces and saturates at a lower value. This behaviour could be attributed to specific physical processes occurring at different frequencies. The relatively smaller value of capacitance drops from nearly 8.6935 nF to 8.6915 nF in the frequency range of 10⁶ Hertz, as depicted in Fig. 14. The capacitance of algal green-synthesized Au is much higher than the earlier reports from Bhattarai et al. for an MASnI₃-based PSC.⁶

Fig. 14 Capacitance analysis of the designed PSC device after all-round optimization techniques.

For PSCs created with MASnI₃, the variation in QE with incident photon wavelength is presented in Fig. 15. The absorption of the perovskite materials can be understood with the help of the QE parameter of the PSC. The bandgap involving the absorbing layer presents an inverse relation with the QE pertinent to solar cells. The device absorbs wavelengths at varied ranges since MASnI₃ has a narrow bandgap (Fig. 15). Comparatively, the current relevant simulation of an MASnI₃-based PSC achieves an average QE of 90%, which is reasonably more optimised than the report mentioned above by Bhattarai et al.³¹ Apart from that, a detailed comparison with earlier works is given in Table 2.

Fig. 15 Quantum efficiency (QE) with wavelength (nm) of the designed PSC device after all-round optimization techniques.

Table 2 A comparison of the PV parameters of the simulated device with earlier work

Device structures	JSC (mA cm^−2)	VOC (V)	FF (%)	PCE (%)
PSC device (present work)	31.31	1.05	80.98	26.60
Du et al.^44	23.36	0.92	79.99	23.36
Singh et al.^45	25.75	1.00	79.21	20.58
Alipour et al.^46	24.65	1.12	86.02	23.69

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5. Conclusions

In conclusion, the most critical solar cell attributes were analysed using the carrier transport approach in the green-synthesized carrier transport layer with reference to MASnI₃-based PSC devices, and the most critical solar cell attributes were analysed. The electric parameter is predicted to be significantly more affected by the active layer appertaining to the PSC designs than by the carrier transport layers (CTLs). Therefore, PAL has been optimized for the simulated device. We obtained an appropriate active layer thickness (0.9 μm) for an MASnI₃-based PSC. The green-synthesized HTL and ETL, CuCrO₂ and CeO₂, also improved the efficiency of the PSC device. Additionally, algae-synthesized Au nanoparticles are used as the back contact, notably being very productive so far as the cost and the overall development of the device are concerned. The capacitance and impedance analysis (imaginary vs. real Z) were also performed for the device architectures appertaining to the doping conditions to assess the dependence of the PSC device on the MASnI₃ materials. The optimized PSC device achieves an excellent PCE of 26.60% for device fabrication. The study also provides a critical recommendation as well as a demonstration to help in the effective manufacturing of an MASnI₃-based PSC.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

The authors would like to express their sincere gratitude to Dr Marc Burgelman and his staff at the University of Gent Belgium for providing the open-source SCAPS-1D simulation software.

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