Phosphonic Acid Modification of the Electron Selective Contact: Interfacial Effects in Perovskite Solar Cells

The role electron-transport layers (ETLs) play in perovskite solar cells (PSCs) is still widely debated. Conduction band alignment at the perovskite/ETL interface has been suggested to be an important role for the performance of the solar cells. However, little is known about the effects of work-function shifts on the solar-cell performance, and specifically, the open-circuit voltage (V-OC). Here, the effects of surface modification of SnO2 ETLs using polar phosphonic acids are investigated, including the effects on work function, surface energy, device performance, and device stability in inert atmosphere. The phosphonic acid modifications did not have a large effect on V-OC; however, a sharp decrease in the overall device performance was found, mostly due to reduced fill factors. When exposed to conditions of low oxygen concentration, the phosphonic acid surface modified devices yielded current-voltage (J-V) curves with considerably lower hysteresis than those based on unmodified SnO2. This suggests that this modification method may be valuable for achieving stabilized power conversion efficiency without hysteresis.

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Juan-Pablo Correa-Baena, Ulf Anders Hagfeldt, Rebecca Hill, Wolfgang Richard Tress, Silver Hamill Turren Cruz
AMER CHEMICAL SOC, 2019
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https://infoscience.epfl.ch/record/266906?ln=en

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Related concepts (12)

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Perovskite solar cell

A perovskite solar cell (PSC) is a type of solar cell that includes a perovskite-structured compound, most commonly a hybrid organic–inorganic lead or tin halide-based material as the light-harvestin

Solar cell

A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical phenomenon. It is a form of p

Surface energy

In surface science, surface free energy (also interfacial free energy or surface energy) quantifies the disruption of intermolecular bonds that occurs when a surface is created. In solid-state physi

Highly efficient, stable and hysteresis-less planar perovskite solar cell based on chemical bath treated Zn2SnO4 electron transport layer

Seckin Akin, Michael Graetzel, Ulf Anders Hagfeldt, Marco Alejandro Ruiz Preciado, Faranak Sadegh, Mohammad Mahdi Tavakoli, Wolfgang Richard Tress, Zaiwei Wang

The electron transport layer (ETL) is a key constituent in perovskite solar cells (PSCs). It should provide efficient and selective electron extraction, low resistivity and high stability. Here, zinc stannate (Zn2SnO4, ZSO) is employed as an ETL in planar PSCs. A surface treatment of a compact ZSO layer is introduced based on chemical bath deposition (CBD). CBD results in a dense and uniform surface morphology that promotes the formation of a perovskite film with better surface coverage and enlarged grains, which lead to reduced recombination losses. Such improvements effectively increase the charge extraction at ETL/perovskite interface and reduce trapassisted recombination, which results in a remarkable photovoltaic performance, low hysteresis index, and good reproducibility. The efficiency of PSCs based on CBD-modified ZSO ETL has been dramatically increased from 19.3% to 21.3% with a notable increase in open circuit voltage of 60 mV compared to bare ZSO-based devices. This value is among the highest for ZSO-based PSCs. More importantly, the CBD-treated PSCs exhibited good stability, retaining more than 90% of its initial efficiency over 1000 h under continuous illumination at maximum power point. These results demonstrate that CBD can significantly improve the performance and stability of ZSO-based planar PSCs, a crucial requirement for commercialization.

ELSEVIER2020

Dye-Sensitized Nanostructured p-Type Nickel Oxide Film as a Photocathode for a Solar Cell

Ulf Anders Hagfeldt

Nanostructured NiO film was prepd. by depositing nickel hydroxide slurry on conducting glass and sintering at 500 °C to a thickness of about 1 μm. The photocurrent-voltage (IV) characteristics of the plain nanostructured NiO electrode recorded potentiostatically in a std. three-electrode setup upon UV illumination demonstrate p-type behavior, while the IV characteristics of a dye-sensitized nanostructured NiO electrode coated with erythrosin B show cathodic photocurrent under visible light illumination. The highest incident photon-to-current conversion efficiencies of tetrakis(4-carboxyphenyl)porphyrin (TPPC) and erythrosin B-coated NiO films were 0.24% and 3.44%, resp. In sandwich solar cells with a platinized conducting glass as counter electrode exposed to light from a sun simulator (light intensity: 68 mW/cm2), a short-circuit cathodic photocurrent d. (ISC) of 0.079 mA/cm2 and an open-circuit voltage (VOC) of 98.5 mV for TPPC-coated NiO electrode were achieved. Similarly, ISC = 0.232 mA/cm2 and VOC = 82.8 mV were registered when the NiO electrode was coated with erythrosin B. The cathodic photocurrent is explained by hole injection from dye mol. to the valence band of the p-NiO electrode.

1999

Three donor-linker-acceptor triphenylamine-based cyanoacrylic acid org. dyes used for dye-sensitized solar cells (DSCs) were examd. with respect to their effect on the open-circuit voltage (Voc). The previous study showed a decrease in Voc for DSCs based on dyes with increased mol. size (increased linker conjugation). The authors study the origin of Voc with respect to (a) conduction band (ECB) positions of TiO2 and (b) degree of recombination between electrons in TiO2 and electrolyte acceptor species at the interface. These parameters were studied as a function of dye structure, dye load, and I2 concn. Two types of behavior were identified: the smaller polyene dyes show a surface-protecting effect preventing recombination upon increased dye loading, whereas the larger dyes enhance the recombination. How the different dye structures affect the recombination is discussed in terms of dye surface blocking and intermol. interactions between dyes and electrolyte acceptor species.

2010