Improved Open‐ Circuit Voltage in ZnO–PbSe Quantum Dot Solar Cells by Understanding and Reducing Losses Arising from the ZnO Conduction Band Tail

Hoye, Robert L. Z.; Ehrler, Bruno; Böhm, Marcus L.; Muñoz‐Rojas, David; Altamimi, Rashid M.; Alyamani, Ahmed Y.; Vaynzof, Yana; Sadhanala, Aditya; Ercolano, Giorgio; Greenham, Neil C.; Friend, Richard H.; MacManus‐Driscoll, Judith L.; Musselman, Kevin P.

doi:10.1002/aenm.201301544

Cited by 97 publications

(140 citation statements)

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“…While we may expect there to be a 0.3 eV electron extraction barrier at the BiOI|ZnO interface, our low-temperature grown ZnO has sub-bandgap states ( Figure S42, Supporting Information) that may accept electrons injected from BiOI. [45] The BiOI|ZnO interface could therefore allow barrier-less electron transport, in agreement with the absence of any kink at the V OC point of our J-V curves (Figure 4c). Therefore, from our PES measurements, we observed band bending of BiOI next to NiO x .…”

supporting

confidence: 86%

“…[46,50] Band tails and sub-bandgap states present in the NiO x ( Figure S43, Supporting Information) and ZnO layers (measured previously, [45,51] and from Figure S42, Supporting Information) can also lead to V OC losses due to carrier thermalization or recombination from the band tails. [45,52] Further device modeling and temperature-dependent V OC measurements are required to quantify the magnitudes of these different effects. However, we would expect that engineering the energy levels and interfaces with charge transport layers discussed above would also lead to improvements in V OC .…”

mentioning

confidence: 67%

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Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

et al. 2017

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Bismuth‐based compounds have recently gained increasing attention as potentially nontoxic and defect‐tolerant solar absorbers. However, many of the new materials recently investigated show limited photovoltaic performance. Herein, one such compound is explored in detail through theory and experiment: bismuth oxyiodide (BiOI). BiOI thin films are grown by chemical vapor transport and found to maintain the same tetragonal phase in ambient air for at least 197 d. The computations suggest BiOI to be tolerant to antisite and vacancy defects. All‐inorganic solar cells (ITO|NiOx|BiOI|ZnO|Al) with negligible hysteresis and up to 80% external quantum efficiency under select monochromatic excitation are demonstrated. The short‐circuit current densities and power conversion efficiencies under AM 1.5G illumination are nearly double those of previously reported BiOI solar cells, as well as other bismuth halide and chalcohalide photovoltaics recently explored by many groups. Through a detailed loss analysis using optical characterization, photoemission spectroscopy, and device modeling, direction for future improvements in efficiency is provided. This work demonstrates that BiOI, previously considered to be a poor photocatalyst, is promising for photovoltaics.

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confidence: 86%

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confidence: 67%

Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

et al. 2017

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“…19,27,30,163 A method to visualize gap states is to plot the leading edge on a semilogarithmic scale, since band tails can be described by exponential functions. 172,173 This is illustrated in Figure 6a for organic small molecules. By using a semilogarithmic plot, the gap states and valence band density of states may be distinguished.…”

Section: Fitting the Leading Edge In Photoemission Spectroscopy Measumentioning

confidence: 99%

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

et al. 2017

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ABSTRACT:Recently, there has been an explosive growth in research based on hybrid lead-halide perovskites for photovoltaics owing to rapid improvements in efficiency. The advent of these materials for solar applications has led to widespread interest in understanding the key enabling properties of these materials. This has resulted in renewed interest in related compounds and a search for materials that may replicate the defect-tolerant properties and long lifetimes of the hybrid lead-halide perovskites. Given the rapid pace of development of the field, the rises in efficiencies of these systems have outpaced the more basic understanding of these materials. Measuring or calculating the basic properties, such as crystal/electronic structure and composition, can be challenging because some of these materials have anisotropic structures, and/or are composed of both heavy metal cations and volatile, mobile, light elements. Some consequences are beam damage during characterization, composition change under vacuum, or compound effects, such as the alteration of the electronic structure through the influence of the substrate. These effects make it challenging to understand the basic properties integral to optoelectronic operation. Compounding these difficulties is the rapid pace with which the field progresses. This has created an ongoing need to continually evaluate best practices with respect to characterization and calculations, as well as to identify inconsistencies in reported values to determine if those inconsistencies are rooted in characterization methodology or materials synthesis. This article describes the difficulties in characterizing hybrid lead-halide perovskites and new materials, and how these challenges may be overcome. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 challenges discussed. The focus in this article is on crystallography, composition measurements, photoemission spectroscopy and calculations on perovskites and new, related absorbers. We suggest how some of the important artifacts could be avoided and how the reporting for each technique could be streamlined between groups to ensure reproducibility as the field progresses.

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“…Células solares que utilizam QDs de ZnO têm sido investigadas ao longo dos últimos anos, [118][119][120] devido às vantagens que este material apresenta quando comparado com o filme de TiO 2 , comumente utilizado para este fim. O ZnO tem uma maior mobilidade eletrônica e, além disso, pode apresentar estruturas anisotrópicas (como nanofios, nanobastões e nanotubos), resultando em propriedades eletrônicas e ópticas únicas.…”

Section: Células Solaresunclassified

Pontos quânticos ambientalmente amigáveis: destaque para o óxido de zinco

Sandri¹,

Krieger²,

Costa³

et al. 2017

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ENVIRONMENTALLY FRIENDLY QUANTUM DOTS: HIGHLIGHTING ZINC OXIDE. Semiconductor nanocrystals with sizes in the quantum confinement regime (2-10 nm) present special physical and chemical properties. Additionally, environment-friendly quantum dots (QDs), as zinc oxide and zinc sulfide, offer many practical usages. Herein the ZnO semiconductor nanocrystals properties will be preferentially explored, such as its luminescence, broad spectrum UV absorber and electronics performances, and therefore its multifunctionality, as well as its advantages compared to some toxics QDs. A review is carefully presented stressing some synthesis approaches for applications reasons toward devices, chemosensors, biological labels, UV-absorbers and photocatalysis. ZnO QDs have been used in combination with organic and other inorganic materials. Hybrid materials have many advantages compared to their individual contents leading to important contributions to science and technology. As a result, an important growth in material fields is noticeable.Keywords: ZnO quantum dots; environment-friendly quantum dots; photocatalysis; UV-blockers; size-dependent fluorescence emission. INTRODUÇÃOÉ notória a contribuição da nanotecnologia nas ciências biológi-cas, farmacêuticas e da saúde nestas últimas três décadas. Como resultado, tem-se observado uma oferta cada vez maior de novos materiais, inteligentes e funcionais, o melhoramento da qualidade de vida das pessoas e, consequentemente, um aumento na expectativa de vida. 1No início da década de 1980 apareceram os primeiros estudos para uma nova classe de nanocristais com capacidade de exibir propriedades espectroscópicas dependentes do tamanho, 2 advindas do efeito de confinamento quântico.3-5 O confinamento quântico é resultado da mudança da densidade dos estados eletrônicos, que por sua vez, está relacionada com a posição e momento para partículas livres e confinadas. Quando a energia e o momento são definidos, a posição destas partículas não pode ser definida com precisão. Se considerada a relação entre energia e momento para a fase sólida massiva, é como pensar que uma série de vibrações que ocorrem com pequenas diferenças de energia nesta fase serão comprimidas, gerando uma transição intensa e única em um ponto quântico (QD, do inglês quantum dot).5 Dita de outra maneira, com a redução do tamanho das partículas a excitação eletrônica é deslocada para regiões de maior energia e o oscilador fica com restrita capacidade de transição. A Figura 1 ilustra a densidade de estados partindo de um material massivo, tridimensional (a) e que, progressivamente, sofre o confinamento em uma das dimensões (b)-(d). 5QDs podem confinar transportadores de cargas e manter uma coerência de spin destes transportadores em um período de tempo maior que os correspondentes materiais massivos, característica essa fundamental para o desenvolvimento de tecnologia baseada em sistemas quânticos 6 e da manifestação de efeitos excitônicos expressivos, os quais dependem da forma e tamanho da estrutura de confinamento. 7A incidênc...

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Improved Open‐ Circuit Voltage in ZnO–PbSe Quantum Dot Solar Cells by Understanding and Reducing Losses Arising from the ZnO Conduction Band Tail

Cited by 97 publications

References 35 publications

Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

Strongly Enhanced Photovoltaic Performance and Defect Physics of Air‐Stable Bismuth Oxyiodide (BiOI)

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

Pontos quânticos ambientalmente amigáveis: destaque para o óxido de zinco

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