Perovskite-based Tandem Solar Cells Research Articles

Tail states suppression via surface-modification of wide-bandgap perovskites for high-efficiency all-perovskite photovoltaic tandems

As an essential light-absorbing material in perovskite-based tandem solar cells, wide-bandgap (WBG) perovskite has garnered extensive attention. Nevertheless, due to severe non-radiative recombination from tail states, as well as photoinduced phase segregation and unoptimized charge transfer, WBG perovskite solar cells (PSCs) typically display significant open-circuit voltage (VOC) loss and low fill factor (FF). In this work, we report to modify the 1.68 eV WBG perovskite film upon optimized surface passivation with 1,3-propane-diammonium iodide (PDAI2). Time-resolved microwave conductivity measurement is employed to analyze the tail states, mobilities of charge carriers and the rate constants of recombination in perovskite films. The results indicate that the optimized surface modification strategy not only enhances film quality, boosts carrier transport, but also suppresses tail states and therefore diminishes non-radiative recombination, consequently elevating the VOC and FF of the device. Hence, the PDAI2-assisted WBG PSCs deliver an optimal efficiency of 21.48 %, accompanied by a VOC of 1.243 V. Furthermore, the integration of a narrow-bandgap tin–lead PSC with a semi-transparent WBG PSC results in a four-terminal perovskite/perovskite tandem solar cell, showcasing an efficiency surpassing 28 %. Our research offers a practical approach for producing efficient WBG PSCs and tandem solar cells.

Surface repair of wide-bandgap perovskites for high-performance all-perovskite tandem solar cells

Wide-bandgap (WBG) perovskite solar cells (PSCs) play a fundamental role in perovskite-based tandem solar cells. However, the efficiency of WBG PSCs is limited by significant open-circuit voltage losses, which are primarily caused by surface defects. In this study, we present a novel method for modifying surfaces using the multifunctional S-ethylisothiourea hydrobromide (SEBr), which can passivate both Pb-I and FA-I terminated surfaces. Moreover, the SEBr upshifted the Fermi level at the perovskite interface, thereby promoting carrier collection. This proposed method was effective for both 1.67 and 1.77 eV WBG PSCs, achieving power conversion efficiencies (PCEs) of 22.47% and 19.90%, respectively, with VOC values of 1.28 and 1.33 V, along with improved film and device stability. With this advancement, we were able to fabricate monolithic all-perovskite tandem solar cells with a champion PCE of 27.10%. This research offers valuable insights for passivating the surface trap states of WBG perovskite through rational multifunctional molecular engineering.

SCAPS-FDTD simulation of 20.1 % efficient Perovskite-SnS tandem solar cell based on alternative charge transport layers and Au-nanoparticles

Perovskite-based tandem solar cells emerged as potential candidates for efficient photovoltaic applications. These devices exhibit high optical absorption properties and tunable direct band-gap. In this work, a novel lead-free Perovskite-SnS Tandem solar cell based on alternative charge transport layers combined with plasmonic-based light management approach is proposed. Accurate numerical investigation is carried out to assess the influence of the charge transport layers of top sub-cell on the optoelectronic properties of the tandem cell. The obtained results reveal the potential of SnO2 and CuO materials as electron and hole transport layers, respectively, demonstrating a good conduction band offset (CBO) and thereby enhanced recombination losses. Furthermore, the role of Gold-nanoparticles in enhancing absorption and light-trapping mechanisms in the bottom SnS-based sub-cell is investigated using FDTD computations. It is found that the optimized tandem cell with Au-NPs exhibits a high power conversion efficiency of 20.1%. Therefore, this work can open up new paths to boost the power conversion of Sn-based Perovskite/SnS Tandem cells for high-performance and eco-friendly photovoltaic applications.

Elucidating Charge Carrier Dynamics in Perovskite-Based Tandem Solar Cells.

Recently, multijunction tandem solar cells (TSCs) have presented high power conversion efficiency and revealed their immense potential in photovoltaic evolution. It is demonstrated that multiple light absorbers with various bandgap energies overcome the Shockley-Queisser limit of single-junction solar cells by absorbing the wide-range wavelength photons. Here, the main key challenges are reviewed, especially the charge carrier dynamics in perovskite-based 2-terminal (2-T) TSCs in terms of current matching, and how to manage these issues from a vantage point of characterization. To do this, the effect of recombination layers, optical and fabrication hurdles, and the impact of wide bandgap perovskite solar cells are discussed extensively. Afterward, this review focuses on various optoelectronics, spectroscopic, and theoretical (optical simulation) characterizations to figure out those issues, especially current-matching issues faced by the photovoltaic society. This review comprehensively provides deep insights into the relationship between the current-matching problems and the photovoltaic performance of TSCs through a variety of perspectives. Consequently, it is believed that this review is essential to address the main problems of 2-T TSCs, and the suggestions to elucidate the charge carrier dynamics and its characterization may pave the way to overcome such obstacles to further improve the development of 2-T TSCs in relation to the current-matching problems.

Compact-porous hole-transport-layer for highly efficient near-infrared region transparent perovskite solar cells for tandem applications

Wide-bandgap perovskites solar cells (PSCs) are vital as top cells in perovskite-based tandem solar cells (TSCs). However, poor band alignment with the charge transport layer and unwanted parasitic absorption in the top semitransparent-PSC (ST-PSC) are major factors limiting the power conversion efficiency (PCE) of TSCs. Herein, we present a compact-porous nickel oxide (cp-NiOx) hole-transport layer (HTL) sequentially fabricated using a sol-gel suspension and colloidal suspension of highly crystalline NiOx. The cp-NiOx film exhibited enhanced transparency, mesoporous surface morphology, and better energy band alignment with a 1.68 eV perovskite film for fabricating highly near-infrared transparent (∼92 % (@800–1200 nm)) ST-PSCs. The best cell achieved a PCE of 15.9 %. In addition, a four-terminal perovskite/silicon TSC based on the cp-NiOx HTL achieved an outstanding PCE of ∼26.0 %. The tailored energy band structure and reduced parasitic absorption in the near-infrared region of the ST-PSCs based on the cp-NiOx HTL enabled fabrication of highly efficient inverted ST-PSCs for perovskite/silicon TSCs.

Ultrathin chromium oxide buffer layer by reactive thermal deposition for high-performance semitransparent perovskite solar cells

Transparent conductive oxide (TCO) films are widely used for semitransparent perovskite solar cells (st-PSCs) and perovskite-based tandem solar cells due to their high optical transparency and good electrical conductivity. However, the high-power sputtering damage during the deposition of TCO film is a vital factor to prevent the perovskite-based solar cells from achieving high efficiency. In this work, we develop an ultrathin chromium oxide (CrOx) buffer layer between the hole transporting layer (HTL) and indium-doped tin oxide (ITO) by trace-oxygen reactive thermal deposition (to-RTD). The experimental results show that the CrOx buffer layer can hinder the sputtering damage of ITO deposition and ensure a high-performance device, which can be attributed to the improved conductivity of the HTL/CrOx/ITO structure together with the tailored energy level alignment. In addition, this buffer layer with a thickness of 4 nm displays a high optical transmittance (>95%) in the interested wavelengths, meaning a limited optical parasitic absorption loss. As a result, the st-PSC with CrOx buffer layer achieves champion power conversion efficiency (PCE) of 19.06%, which is one of the highest PCEs for the n-i-p st-PSCs. Moreover, a four-terminal perovskite/silicon tandem solar cell featuring a CrOx buffer layer realizes a relatively high PCE of 27.48%.

钙钛矿叠层太阳电池中电荷传输材料的研究进展

Developing perovskite-based tandem solar cells (TSCs) is a promising technique to surpass the Shockley-Queisser limit set for single-junction solar cells. Encouragingly, all the perovskite-based TSCs, including perovskite/silicon, perovskite/perovskite, perovskite/copper indium gallium selenide and perovskite/organic tandems have demonstrated higher efficiency than the corresponding single-junction solar cells, showing great potential for further breakthroughs. In tandem devices, charge transport materials (CTMs) are vital components of perovskite sub-cells that directly determine the charge transportation and energy loss. Generally, high conductivity and transmittance, favorable energy-level alignment and chemical stability are crucial for CTMs for tandem applications. To date, various CTMs including conductive metallic oxides, organic molecules, polymers, fullerenes, and self-assembled materials have been extensively employed in highly efficient TSCs. In this review, we first summarize the recent progress of CTMs for different types of monolithic perovskite-based TSCs, in which the electrical and optical properties of CTMs and their influence on device performance are carefully discussed. Then we put forward the challenges and outlook for the further development of CTMs for tandem applications. This comprehensive review will provide effective guidance for device design for different perovskite-based TSCs.

Amino-acid-type alkylamine additive for high-performance wide-bandgap perovskite solar cells

A wide-bandgap (WBG) perovskite top component cell is vital for all perovskite-based tandem solar cells. However, such WBG perovskite solar cell (PSC) suffers from inferior crystallinity, huge voltage loss and poor photostability. Herein, we report a amino-acid-type alkylamine, 5-aminolevulinic acid hydrochloride (ALH) additive to address these issues to enhance the performance of WBG PSCs. It is found that the ALH effectively modulates the perovskite crystallization via chemical complexation between the ALH and PbI2, and enhances the crystallinity of the perovskite film. Moreover, the amino acid ALH not only passivates negatively charged deep-level IFA and IPb anti-site defects via –NH3+ terminals to reduce voltage loss, but also suppresses photo-induced phase segregation via the coordination between –COO− groups and halide vacancies. With these merits, the ALH-based PSC delivers an excellent power-conversion efficiency (PCE) of 21.13%, one of the highest values for inverted WBG PSCs. In addition, the air and thermal stability are also significantly improved. Our findings provide a feasible approach to prepare highly efficient and stable WBG PSCs.

Wide-Band-Gap (2.0 eV) Perovskite Solar Cells with a VOC of 1.325 V Fabricated by a Green-Solvent Strategy.

Perovskite-based tandem solar cells are promising candidates for next-generation photovoltaic devices. However, the defects caused by ion migration cause a large deficit of open-circuit voltage (VOC) in conventional wide-band-gap perovskite films. Here, we present a new strategy that employs nontoxic acetic acid and isopropanol as solvents to deposit a perovskite film with a 2.0 eV band gap in an ambient atmosphere. The in situ formed acetate anions strongly stabilize the intrinsic defects in perovskite films. These features effectively improve the phase stability of 2.0 eV Cs0.2FA0.8PbI0.9Br2.1 perovskite, allowing the VOC to reach 1.325 V and the corresponding power conversion efficiency to reach 10.62%, which is close to the state-of-art performance of perovskite solar cells employing perovskite around a 2.0 eV band gap.

Perovskite/organic tandem solar cells: a review

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has rapidly increased and exceeded 25% based on strategies such as interface modification, doping engineering, and optimization of preparation methods. further improvement seems to have entered a bottleneck period due to Shockley-Quiesser (S-Q) limit of single-junction devices. Tandem cell designed to achieve efficient matching of a wider range of the solar spectrum is considered a successful method to solve this difficulty. In tandem architecture, the PSC is a perfect top-cell candidate owing to its large absorption coefficient, adjustable band gap, and feasible low-temperature solution processibility. The perovskite-based tandem solar cells (TSCs) such as perovskite-silicon, perovskite-perovskite, and perovskite-organic devices have stimulated enormous research interest and got significant progress in the past few years. Among them, the abundant perovskite and organic semiconductor materials with tunable components, adjustable bandgap, and various physical and chemical properties make the perovskite/organic TSCs (PO-TSCs) more competitive. In this work, a general introduction and review of recent advances in perovskite/organic tandem features are provided. In addition, a perspective and some suggestions about future developments in this field are also discussed.

Two-Terminal Perovskite Tandem Solar Cells: from Design to Commercial Prospect

Tandem Solar Cells (TSCs) with multi-junction are capable to break the SQ limit and achieve high PCE through absorbing larger range of light wavelength by multiple absorber layers with different band gaps. Perovskite solar cells are ideal light absorbing materials for TSC because of its high PCE, high suitability with other absorbers, low cost and easy fabrication. Perovskite-based TSCs have so far outperformed single-junction devices in PCE, garnering considerable interest from both academia and material industry. In this review, the basic science of perovskite Tandem Solar Cells (PTSCs) is presented, as well as the construction and properties of PSC as a top cell. Then three main types of PTSCs are introduced: Perovskite/Si, Perovskite/CIGS, and Perovskite/Perovskite including their design, challenges and fabrication methods. Finally, the current status and future prospects for commercialization of PTSCs are also discussed. According to recent developments, PTSCs are considered to be one of the most promising solar cells. Research on PTSCs could contribute to the development of desirable clean energy sources in order to solve the energy crisis and environmental problems of human beings.

Highly efficient and stable hole-transport-layer-free inverted perovskite solar cells achieved 22% efficiency through p-type molecular synergistic doping

low-cost, facile manufacturing processes are becoming more and more important for commercialization of perovskite solar cells (PSCs). In this aspect, the development of hole-transport-layer-free (HTL-free) PSC is particularly important. In this paper, we fabricated HTL-free PSC with improved photovoltaic performance via synergistic doping Cu(thiourea)Cl (Cu(Tu)Cl) and thiosemicarbazide into the perovskite precursor solution to obtain high-quality perovskite films with average grains of more than 1 µm. This synergistic doping strategy can simultaneously decrease perovskite surface and internal defects and mitigate interfacial energy barrier, which is superior to the present single passivation method which brings about defect passivation deficiency. As a result, compared to the control device with the efficiency of 13.10%, the HTL-free perovskite device prepared by synergistic doping strategy achieves a remarkable PCE of 22% with almost negligible hysteresis, which is the highest PCE values reported so far for the HTL-free PSCs. In addition, the environmental, thermal and long-term operational stabilities of the optimized devices prepared by synergistic doping strategy are significantly improved compare to the control devices. Especially, the unencapsulated optimized device retains 90% of the original efficiency under continuous illumination (100 mW cm−2) for 1000 h with the maximum power point (MPP) tracking in nitrogen-filled test box. Furthermore, this strategy has been shown to be effective in wide-bandgap perovskite. The wide-bandgap perovskite Cs0.05MA0.15FA0.8Pb(I0.75Br0.25)3 (1.65 eV) based HTL-free device achieves a PCE of 19.7% with an Voc of 1.2 V, which is the highest PCE values reported so far for the HTL-free wide-bandgap PSCs, which opens a new way to fabricate HTL-free perovskite-based tandem solar cells. This work manifests a noteworthy step towards the facile, cost-efficient fabricating of PSCs with both high efficiency and simple manufacturing processes.

Dually Modified Wide-Bandgap Perovskites by Phenylethylammonium Acetate toward Highly Efficient Solar Cells with Low Photovoltage Loss.

Wide-bandgap perovskites as a class of promising top-cell materials have shown great promise in constructing efficient perovskite-based tandem solar cells, but their intrinsic relatively low radiative efficiency results in a large open-circuit voltage (VOC) deficit and thereby limits the whole device performance. Reducing film flaws or optimizing interfacial energy level alignments in wide-bandgap perovskite devices can efficiently inhibit nonradiative recombination to boost device VOC and efficiency. However, the simultaneous regulation on both sides and their underlying mechanism are less explored. Herein, a bifunctional modification approach is proposed to optimize the wide-bandgap perovskite surface with an ultrathin layer of phenylethylammonium acetate (PEAAc) to synchronously decrease the surface imperfection and mitigate the interfacial energy barrier. This treatment effectively heals under-coordinated surface defects through the formation of chemical interaction between the perovskite and PEAAc, bringing about a much slower charge trapping process and dramatically decreasing nonradiative recombination losses. Meanwhile, the passivation-induced upshifted Fermi level of the perovskite contributes to accelerated electron extraction and larger Fermi-level splitting under illumination. Consequently, the PEAAc-modified wide-bandgap (1.68 eV) device achieves an optimal efficiency of 20.66% with a high VOC of 1.25 V, among the highest reported VOC values for wide-bandgap perovskite devices, enormously outperforming that (18.86% and 1.18 V) of the device without passivation. In addition, the radiative limit of VOC for both cells is determined to be 1.42 V, delivering nonradiative recombination losses of 0.24 and 0.17 V for the control and PEAAc-modified devices, respectively. These results highlight the significance of the bifunctional modification strategy in achieving high-performance wide-bandgap perovskite devices.

Tin dioxide buffer layer-assisted efficiency and stability of wide-bandgap inverted perovskite solar cells

Inverted perovskite solar cells (IPSCs) have attracted tremendous research interest in recent years due to their applications in perovskite/silicon tandem solar cells. However, further performance improvements and long-term stability issues are the main obstacles that deeply hinder the development of devices. Herein, we demonstrate a facile atomic layer deposition (ALD) processed tin dioxide (SnO2) as an additional buffer layer for efficient and stable wide-bandgap IPSCs. The additional buffer layer increases the shunt resistance and reduces the reverse current saturation density, resulting in the enhancement of efficiency from 19.23% to 21.13%. The target device with a bandgap of 1.63 eV obtains open-circuit voltage of 1.19 V, short circuit current density of 21.86 mA/cm2, and fill factor of 81.07%. More importantly, the compact and stable SnO2 film invests the IPSCs with superhydrophobicity, thus significantly enhancing the moisture resistance. Eventually, the target device can maintain 90% of its initial efficiency after 600 h storage in ambient conditions with relative humidity of 20%–40% without encapsulation. The ALD-processed SnO2 provides a promising way to boost the efficiency and stability of IPSCs, and a great potential for perovskite-based tandem solar cells in the near future.

Perovskite/Silicon Tandem Solar Cells with a Voc of 1784 mV Based on an Industrially Feasible 25 cm2 TOPCon Silicon Cell

Perovskite-based tandem solar cells are promising candidates for industrial applications. This study demonstrated perovskite/silicon tandem devices based on a conventional Si homojunction device configuration employing a tunnel oxide passivating contact to improve the voltage. Moreover, we fabricated it without the deposition of a recombination layer on a large area while showing the possibility of applying the industry market. This solar cell exhibited a power conversion efficiency of 17.3% and a high voltage of 1783 mV on a 25 cm2 active area.

Iterative method for optical modelling of perovskite-based tandem solar cells.

We present an iterative method to model the optical properties of a complete semitransparent perovskite solar cell. It is based on spectroscopic characterizations and accounts for porosity and incoherence effects. We provide the complex refractive indices of each layer, and we identify the main sources of optical losses. The optical model is also coupled to an electrical model of 4T perovskite/silicon tandem solar cells. It allows to evaluate the interplay between the optical and electrical losses, and the balance between the efficiency of the top and bottom cells. These models provide an effective way to design future tandem devices.

Perovskite-based tandem solar cells gallop ahead

Perovskite-based tandem cells as clean photovoltaic conversion devices drive the transition to decarbonized energy. Recently in <i>Nature</i>, Tan and co-workers report a certified efficiency of 26.4%, a record-setting efficiency in all-perovskite tandem solar cells. High photocurrent density is achieved by ammonium cation passivation, addressing the short carrier diffusion length in thick mixed Pb-Sn narrow-bandgap subcell.

Two-Terminal Perovskite-Based Tandem Solar Cells for Energy Conversion and Storage.

The organic-inorganic hybrid perovskite solar cells present a rapid improvement on power conversion efficiency from 3.8% to 25.5% in the past decades. Owing to the tuneable bandgaps, low-cost, and ease of fabrication, perovskites become ideal candidate materials for fabricating tandem solar cells, especially for efficient and high-voltage monolithic two-terminal devices. In this review, an overview of recent advances in various monolithic perovskite-based tandem solar cells with a focus on the key challenges is provided. Subsequently, the recombination layer materials, construction of wide-bandgap perovskite layer, stability of narrow-bandgap, and current matching principle in tandems are highlighted in order to optimize the output voltage and conversion efficiency of tandem solar cells. Finally, the recent progress is summarized with a focus on potential applications of tandem solar cells for energy conversion and storage, including hydrogen production by water splitting, CO2 reduction, supercapacitors, and rechargeable batteries, benefiting from the adjustable output voltage of tandem solar cells. It is hoped that this work can offer a feasible strategy to explore more possibilities for fabricating new two-terminal tandem solar cells with high voltage and high conversion efficiency for energy conversion and storage.

Efficient wide-bandgap perovskite solar cells enabled by doping a bromine-rich molecule

Abstract Wide-bandgap (wide-E g , ∼1.7 eV or higher) perovskite solar cells (PSCs) have attracted extensive attention due to the great potential of fabricating high-performance perovskite-based tandem solar cells via combining with low-bandgap absorbers, which is considered promising to exceed the Shockley–Queisser efficiency limit. However, inverted wide-E g PSCs with a minimized open-circuit voltage (V oc) loss, which are more suitable to prepare all-perovskite tandem devices, are still lacking study. Here, we report a strategy of adding 1,3,5-tris (bromomethyl) benzene (TBB) into wide-E g perovskite absorber to passivate the perovskite film, leading to an enhanced average V oc. Incorporation of TBB prolongs carrier lifetimes in wide-E g perovskite due to reduction of defects in perovskites and makes a better energy level matching between perovskite absorber and electron transport layer. As a result, we achieve the power conversion efficiency of 17.12% for our inverted TBB-doped PSC with an enhanced V oc of 1.19 V, compared with that (16.14%) for the control one (1.14 V).

Transparent Electrode Techniques for Semitransparent and Tandem Perovskite Solar Cells

Inorganic–organic halide perovskite solar cells have attracted significant attention to the photovoltaic community considering their high-efficiency, tunable bandgap, low-cost, and easy fabrication. Perovskite solar cells are especially an attractive top cell partner for tandem applications with silicon bottom cells and other solar cell types with lower bandgap absorbers. For such tandem applications, semitransparent perovskite solar cell techniques with high near-infrared transparency become important, since the incident light needs to efficiently reach the bottom cell. This review article will summarize the status and progress of perovskite-based tandem solar cells development, while focusing on the transparent electrode approaches and techniques. Future directions and challenges of transparent electrodes for semitransparent and tandem perovskite-based photovoltaics will also be discussed.