scholarly journals Probing the ionic defect landscape in halide perovskite solar cells

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Sebastian Reichert ◽  
Qingzhi An ◽  
Young-Won Woo ◽  
Aron Walsh ◽  
Yana Vaynzof ◽  
...  

AbstractPoint defects in metal halide perovskites play a critical role in determining their properties and optoelectronic performance; however, many open questions remain unanswered. In this work, we apply impedance spectroscopy and deep-level transient spectroscopy to characterize the ionic defect landscape in methylammonium lead triiodide (MAPbI3) perovskites in which defects were purposely introduced by fractionally changing the precursor stoichiometry. Our results highlight the profound influence of defects on the electronic landscape, exemplified by their impact on the device built-in potential, and consequently, the open-circuit voltage. Even low ion densities can have an impact on the electronic landscape when both cations and anions are considered as mobile. Moreover, we find that all measured ionic defects fulfil the Meyer–Neldel rule with a characteristic energy connected to the underlying ion hopping process. These findings support a general categorization of defects in halide perovskite compounds.

Author(s):  
Thomas Kirchartz

One of the most significant features of lead-halide perovskites is their ability to have comparably slow recombination despite the fact that these materials are mostly processed from solution at room temperature. The slow recombination allows achieving high open-circuit voltages when the lead-halide perovskite layers are used in solar cells. This perspective discusses the state of the art of our understanding and of experimental data with regard to recombination and open-circuit voltages in lead-halide perovskites. A special focus is put onto open questions that the community has to tackle to design future photovoltaic and optoelectronic devices based on lead-halide perovskites and other semiconductors with similar properties. This article is part of a discussion meeting issue ‘Energy materials for a low carbon future’.


Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 667 ◽  
Author(s):  
Edson Meyer ◽  
Dorcas Mutukwa ◽  
Nyengerai Zingwe ◽  
Raymond Taziwa

Perovskite solar cells employ lead halide perovskite materials as light absorbers. These perovskite materials have shown exceptional optoelectronic properties, making perovskite solar cells a fast-growing solar technology. Perovskite solar cells have achieved a record efficiency of over 20%, which has superseded the efficiency of Gräztel dye-sensitized solar cell (DSSC) technology. Even with their exceptional optical and electric properties, lead halide perovskites suffer from poor stability. They degrade when exposed to moisture, heat, and UV radiation, which has hindered their commercialization. Moreover, halide perovskite materials consist of lead, which is toxic. Thus, exposure to these materials leads to detrimental effects on human health. Halide double perovskites with A2B′B″X6 (A = Cs, MA; B′ = Bi, Sb; B″ = Cu, Ag, and X = Cl, Br, I) have been investigated as potential replacements of lead halide perovskites. This work focuses on providing a detailed review of the structural, optical, and stability properties of these proposed perovskites as well as their viability to replace lead halide perovskites. The triumphs and challenges of the proposed lead-free A2B′B″X6 double perovskites are discussed here in detail.


Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1324
Author(s):  
Wentao Zhang ◽  
Zeyulin Zhang ◽  
Qubo Jiang ◽  
Ziming Wei ◽  
Yuting Zhang ◽  
...  

The inorganic perovskite has a better stability than the hybrid halide perovskite, and at the same time it has the potential to achieve an excellent photoelectric performance as the organic-inorganic hybrid halide perovskite. Thus, the pursuit of a low-cost and high-performance inorganic perovskite solar cell (PSC) is becoming the research hot point in the research field of perovskite devices. In setting out to build vacuum-free and carbon-based all-inorganic PSCs with the traits of simple fabrication and low cost, we propose the ones with a simplified vertical structure of FTO/CsPbIBr2/carbon upon interfacial modification with PEI species. In this structure, both the electron-transporting-layer and hole-transporting-layer are abandoned, and the noble metal is also replaced by the carbon paste. At the same time, FTO is modified by PEI, which brings dipoles to decrease the work function of FTO. Through our measurements, the carrier recombination has been partially suppressed, and the performance of champion PSCs has far exceeded the control devices without PEI modification, which yields a power conversion efficiency of 4.9% with an open circuit voltage of 0.9 V and a fill factor of 50.4%. Our work contributes significantly to give an available method to explore charge-transporting-layer-free, low-cost, and high-performance PSCs.


2019 ◽  
Vol 10 (1) ◽  
pp. 1902573 ◽  
Author(s):  
Lisa Krückemeier ◽  
Uwe Rau ◽  
Martin Stolterfoht ◽  
Thomas Kirchartz

Science ◽  
2017 ◽  
Vol 356 (6345) ◽  
pp. 1376-1379 ◽  
Author(s):  
Woon Seok Yang ◽  
Byung-Wook Park ◽  
Eui Hyuk Jung ◽  
Nam Joong Jeon ◽  
Young Chan Kim ◽  
...  

The formation of a dense and uniform thin layer on the substrates is crucial for the fabrication of high-performance perovskite solar cells (PSCs) containing formamidinium with multiple cations and mixed halide anions. The concentration of defect states, which reduce a cell’s performance by decreasing the open-circuit voltage and short-circuit current density, needs to be as low as possible. We show that the introduction of additional iodide ions into the organic cation solution, which are used to form the perovskite layers through an intramolecular exchanging process, decreases the concentration of deep-level defects. The defect-engineered thin perovskite layers enable the fabrication of PSCs with a certified power conversion efficiency of 22.1% in small cells and 19.7% in 1-square-centimeter cells.


Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5039
Author(s):  
Shadrack J. Adjogri ◽  
Edson L. Meyer

Despite the advancement made by the scientific community in the evolving photovoltaic technologies, including the achievement of a 29.1% power conversion efficiency of perovskite solar cells over the past two decades, there are still numerous challenges facing the advancement of lead-based halide perovskite absorbers for perovskite photovoltaic applications. Among the numerous challenges, the major concern is centered around the toxicity of the emerging lead-based halide perovskite absorbers, thereby leading to drawbacks for their pragmatic application and commercialization. Hence, the replacement of lead in the perovskite material with non-hazardous metal has become the central focus for the actualization of hybrid perovskite technology. This review focuses on lead-free hybrid halide perovskites as light absorbers with emphasis on how their chemical compositions influence optical properties, morphological properties, and to a certain extent, the stability of these perovskite materials.


2020 ◽  
Vol 8 (20) ◽  
pp. 10439-10449
Author(s):  
Klara Suchan ◽  
Justus Just ◽  
Pascal Becker ◽  
Eva L. Unger ◽  
Thomas Unold

Optical in situ monitoring tracks crystallization and optoelectronic properties of halide perovskites during growth in a glovebox environment.


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