Energy Level Alignment in Ternary Organic Solar Cells

Lami, Vincent; Hofstetter, Yvonne J.; Butscher, Julian F.; Vaynzof, Yana

doi:10.1002/aelm.202000213

Cited by 21 publications

(17 citation statements)

References 48 publications

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“…The position of the conduction band is then estimated by adding the corresponding optical gap. The method has already been applied to a range of organic and organic/inorganic systems, [21][22][23] and here we apply it for the first time to study the interfacial alignment of 2D/3D perovskites. UPS depth profiling of the three sets of 2D/3D samples reveals significant differences in their interfacial energetic alignment.…”

mentioning

confidence: 99%

2D/3D perovskite engineering eliminates interfacial recombination losses in hybrid perovskite solar cells

Sutanto

Caprioglio

Drigo

et al. 2021

Chem

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143

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Engineering two-dimensional (2D) / three-dimensional (3D) perovskites has emerged as an attractive route to efficient and durable perovskite solar cells. Beyond improving the surface stability of the 3D layer and acting as a trap passivation agent, the exact function of 2D/3D device interface remains vague. Here, we provide evidence that 2D/3D perovskite interface that forms a p-n junction is capable to reduce the electron density at the hole-transporting layer interface and ultimately suppress interfacial recombination. By a novel ultraviolet photoelectron spectroscopy (UPS) depth-profiling technique, we show that engineering of the 2D organic cations, in this case by simply varying the halide counter ions in thiophene methylammonium-salts, modifies the 2D/3D perovskite energy alignment. These measurements enable the true identification of the energetic across the 2D/3D interface, so far unclear. When integrated in solar cells, due to the electron blocking nature of the 2D layer, the optimized 2D/3D structures suppress the interfacial recombination losses, leading to opencircuit voltage (VOC) which approaches the potential internal Quasi-Fermi Level Splitting (QFLS) voltage of the perovskite absorber. The devices exhibit an improved fill factor (FF) driven by the enhanced hole extraction efficiency and reduced electron density at the 2D/3D interface. We thus identify the essential parameters and energetic alignment scenario required for 2D/3D perovskite systems in order to surpass the current limitations of hybrid perovskite solar cell performances.Understanding and exploiting interfacial physics is key in perovskite solar cell engineering and optimization. 1,2 That is especially true when interface losses play a dominant role and complex interface functionalization is essential to minimize them. In the field of hybrid perovskite engineering, much attention has been lately focused on multi-dimensional perovskite interfaces consisting of a wider band gap layered (namely, two dimensional-2D) perovskite deposited between the bulk 3D perovskite and the hole transporting layer (HTL) in a standard mesoporous configuration. [3][4][5][6][7][8][9] Such configuration is currently among the most effective strategies to enhance both the efficiency and stability of perovskite solar cells. 3,10,11 It is generally considered that the 2D perovskite acts as both an efficient mean to passivate the surface traps (leading to reduced defect recombination) and an electron blocking layer due to its wider band gap. [12][13][14][15] However, despite these empirical observations, the energetic alignment at the interface and the relative function of the 2D/3D interface is only qualitatively depicted with a only a partial understanding of these

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mentioning

confidence: 99%

2D/3D perovskite engineering eliminates interfacial recombination losses in hybrid perovskite solar cells

Sutanto

Caprioglio

Drigo

et al. 2021

Chem

Self Cite

143

119

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“…This result is consistent with the minimal HOMO offset (0 eV) between P(F‐BiT)‐COOBOCl(in) and IT‐4F in the CV results, which can be caused by charge carrier recombination. [ 55 ]…”

Section: Resultsmentioning

confidence: 99%

Molecular Design of Efficient Chlorine‐ and Carboxylate‐Functionalized Donor Polymers for Nonfullerene Organic Solar Cells Enabling Processing with Eco‐Friendly Solvent in Air

et al. 2021

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Realizing the commercial applications of nonfullerene organic solar cells (NFOSCs) require a balanced of power conversion efficiency (PCE), production cost, and stability. However, because most high‐performance NFOSC devices contain air‐sensitive donor polymers that have low solubility in eco‐friendly solvents, their fabrication requires halogenated solvents and an inert atmosphere. Herein, an air‐processed inverted NFOSC device is developed using a relatively cost‐effective chlorine‐ and carboxylate‐functionalized bithiophene‐based donor polymer, P(F‐BiT)‐COOBOCl(out). When blended with 3,9‐bis(2‐methylene‐((3‐(1,1‐dicyanomethylene)‐6,7‐difluoro)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (IT‐4F), the resultant device yields a high PCE of 11.91%, with good shelf‐life stability and photostability under ambient conditions without encapsulation, and less performance degradation than most reported NFOSCs. Importantly, when the polymer blend is processed in air with an eco‐friendly solvent, 1,2,4‐trimethylbenzene, the resultant device exhibits a reasonably high PCE of 10.60% (certified PCE: 10.467%) without encapsulation, which is the highest value reported to date for NFOSCs fabricated under such conditions. The potential of this high‐performance and eco‐friendly processable polymer is further demonstrated in the excellent PCE of 14.22% of a device with a P(F‐BiT)‐COOBOCl(out):Y6‐BO‐4Cl blend prepared in o‐xylene solvent. This study provides perspectives and opportunities for designing and developing efficient photoactive materials as a new strategy for the commercialization of NFOSCs.

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“…Ternary cells can be designed with complementary absorption bands to maximise the range of the solar spectrum that the cell absorbs and enhance its power conversion efficiency. In addition, the correlation between the energy levels of the three components of the ternary cells plays a crucial role in the development and optimization of these cells [116]. Good energy level alignment between the components of the ternary cells leads to increased charge transport and collection and thus improved device efficiency.…”

Section: Organic Solar Cellsmentioning

confidence: 99%

Current Status of Emerging PV Technologies: A Comparative Study of Dye-Sensitized, Organic, and Perovskite Solar Cells

Giannouli¹

2021

International Journal of Photoenergy

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The imminent depletion of conventional energy sources has motivated the advancement of renewable energy technologies. Third-generation photovoltaic technologies, such as dye-sensitized solar cells (DSSCs), organic solar cells (OSCs), and perovskite solar cells (PSCs), are being developed as alternatives to silicon solar cells. In recent years, there has been considerable interest in the market development of these emerging photovoltaic technologies, especially for sustainable solar energy applications. However, these technologies have not yet reached the maturity required for large-scale commercialization. Further research is required in order to improve the efficiency and stability of these devices, while keeping their production costs to a minimum. In this study, a comparative assessment of DSSCs, OSCs, and PSCs is conducted and the current state of the art of these promising technologies is investigated. Advanced techniques and research trends are examined from the perspective of novel materials, device modelling, and innovative device structures. The comparative advantages and limitations of each of these photovoltaic technologies are assessed in terms of device efficiency, durability, ease of fabrication, and performance-price ratio. Emphasis is placed on assessing the potential of these solar cell technologies for sustainable solar energy applications. Finally, the future outlook of these technologies is featured, and avenues for progress beyond the state of the art are explored.

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Energy Level Alignment in Ternary Organic Solar Cells

Cited by 21 publications

References 48 publications

2D/3D perovskite engineering eliminates interfacial recombination losses in hybrid perovskite solar cells

2D/3D perovskite engineering eliminates interfacial recombination losses in hybrid perovskite solar cells

Molecular Design of Efficient Chlorine‐ and Carboxylate‐Functionalized Donor Polymers for Nonfullerene Organic Solar Cells Enabling Processing with Eco‐Friendly Solvent in Air

Current Status of Emerging PV Technologies: A Comparative Study of Dye-Sensitized, Organic, and Perovskite Solar Cells

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