Elsevier

Optik

Volume 243, October 2021, 167492
Optik

Carrier transport layer free perovskite solar cell for enhancing the efficiency: A simulation study

https://doi.org/10.1016/j.ijleo.2021.167492Get rights and content

Abstract

The recently developed perovskite solar cell (PSC) has revolutionized photovoltaic technology due to the impressive growth in its efficiency. For the sake of enhancing the power conversion efficiency (PCE), the photo absorber-free layer is stacked in between the best suitable carrier transportation layers (CTLs). But the main challenge is that its interfaces enhance recombination, hysteresis and offer poor stability due to the decisive effect of the CTLs. To counteract such complications, a CTL-free MAPbI3 based PSC is proposed to nullify the impact under the optimization of the perovskite absorbing layer's thickness (PAL). Furthermore, the acceptor and donor doping concentration enhance the efficiency with a density of 3.25 × 1025 m−3 in the PAL. The present simulation is exhibiting a very high short circuit current density (JSC) of 17.53 mA cm−2, an open-circuit voltage (VOC) of about 0.852 Volt, a high fill factor (FF) of 82.67%, and an excellent power conversion efficiency (PCE) of 12.35%, respectively. Thus, the present simulation simultaneously unwraps a new space for the less defective PSC in the near future.

Introduction

The renewable energy source has gained tremendous interest due to the practical implication of its application-centred approach in the recent period. Predominantly, the devices that operate on renewable energy sources have attained worldwide acceptance for their faster optimization and steeply increasing efficiency due to extensive research on solar energy. The photovoltaic (PV) cells effectively convert the sunlight to electrical energy with the help of the incident photons [1], [2], [3], [4], [5]. As the higher generation for the excitons can be effectively triggered due to the influence of significant absorption in the photo-absorption layer [6], [7]. So, materials with a high absorption coefficient are preferable for the application of solar cell. The traditionally preferred material for solar cell fabrication is a silicon-based solar cell for higher efficiencies [8], [9]. But in practical use, it has some intrinsic lacks related to high-quality materials but less absorption coefficient, indirect bandgap, and high cost in fabrication [10]. That's why researchers prefer to use a much efficient and much superior solar cell based on the organic-inorganic halide perovskite materials in PV-based applications. It is better in particular aspects, such as; more significant absorption coefficient [11], higher efficiency [12], [13], [14], high dielectric constant [15], and variable and tunable bandgaps [16], respectively. For all these advantages, the first perovskite solar cell (PSC) was reported with the pioneering work of Kojima et al. attaining an efficiency of 3.8% [17], since then the PCE is steeply increased, and at the current scenario, the PSC reported a much higher value up to 26% with Si material [18] and the further research is still on for improving the efficiency. It is an outstanding result for thin-film perovskite PAL, as no solar technology has ever enhanced the efficiency so rapidly. The perovskite solar cell architecture comprises two carrier transport layers (electron and hole transport materials) and the PAL keeping between them [19]. Since the primary function of the PAL is to absorb maximum photons incident on it and both the CTLs (ETL and HTL) effectively extract and further transport the photogenerated electrons. Apart from these advantages, CTLs can be problematic in certain circumstances. Firstly, defect-free device fabrication is always challenging for its complexity [20]. Secondly, these can enhance recombination and offer hysteresis, respectively [21]. A single PAL with CTL free approach can be effectively proposed to sort out the issues mentioned above. In these consequences, Madan et al. have attained an efficiency of up to 9.7% with a lesser defective perovskite material [22]. Secondly, due to having both the carrier transport materials, the recombination in the PSC device increases, which impact in attaining lesser electron and hole currents. Lastly, the contact plays an essential role in better device outputs and better stability than multiple interfaces device. The CTM free PSC only contains two interface contacts, namely, FTO/MAPbI3 and MAPbI3/Au, which helps in attaining lesser recombination of the carriers, respectively.

The carrier transportation in the PSC is well maintained with the electric fields generated across the MAPbI3 layer for navigating the generated hole and electron towards the opposite electrodes without having the carrier transport materials. The electric field in the device is generated using two different metals (front and back electrodes) of different metal work function. Apart from that, to obtain the improved device parameters, the optimization of PAL thickness is mandatory for providing the best optical absorption and output parameters for the photon to the transmission through the device. As a thinner PAL results in lower excitons generation while the thicker PAL offers higher recombination inside the device, which can tremendously affect the current generation phenomena [23]. In the present simulation, we investigated a MAPbI3 based PSC layer stacking between the electrode for better device parameters with doping concentration 3.25 × 1025 m−3 studies using the SETFOS fluxim 4.6, respectively. The absolute thickness for PAL of the MAPbI3 is also obtained, resulting in better solar cell parameters. Furthermore, the PSC device's electric parameters, such as impedance, potential, and capacitance over distinct parameters, have also been used to obtain better device output.

Section snippets

Simulated device architecture

A heterojunction perovskite solar cell having a configuration of FTO/MAPbI3/Au is considered using a Fluxim simulating software to investigate the CTL free perovskite solar cell as shown in Fig. 1(a). The typical PSC device is constructed with FTO works as a top electrode having 100 nm thickness. In contrast, the perovskite material for the device has a thickness of 600 nm. The anode is Au, which contains a width of 50 nm. However, Fig. 1(b) shows the working mechanism in the PSC corresponding

Results and discussions

The impact of the different thickness of the perovskite active layer, i.e. MAPbI3 on the device output have been investigated for the carrier transport less PSC structure. Apart from that, the effect of defect density of the MAPbI3 is also included in the simulation. The detailed investigations of the PSC have been depicted in Figs. 2−8, respectively.

Conclusions

A computational simulation approach is performed for CTL-free PSC with high doping concentration to obtain better device outcomes under the solar illumination of AM1.5. The thickness optimization up to 800 nm of the PAL, i.e., MAPbI3 exhibiting higher P.V. parameters precisely, JSC of 17.69 mA cm−2, VOC of 0.852 Volt, much improved FF about 82.67% with excellent PCE of 12.35% respectively. The carrier transport in the PSC device is uplifted by the electric field generated through the potential

Declaration of Competing Interest

The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript.

Acknowledgment

The authors acknowledge financial support from the third phase of the Technical Education Quality Improvement Programme Funded by TEQIP-III, MoE, Govt. of India under seed grant through National Institute of Technology-Arunachal Pradesh, India. Author Sagar Bhattarai would also like to express his deep and sincere gratitude to TEQIP-III for providing fellowship to carry out his research work.

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