Spatial mapping of photocurrents in organic solar cells comprising wedge-shaped absorber layers for an efficient material screening

Nickel, Felix; Sprau, Christian; Klein, Michael F. G.; Kapetana, Panagiota; Christ, Nico; Liu, Xin; Klinkhammer, Soenke; Lemmer, Uli; Colsmann, Alexander

doi:10.1016/j.solmat.2012.04.026

Cited by 43 publications

(36 citation statements)

References 25 publications

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“…These parameters include the blade velocity, the total volume of solution forming the reservoir, the gap between substrate and blade, the substrate temperature during deposition and the concentration of the solution. Following previous work, [29] we have altered our doctor blade electronics in order to control speed and acceleration of the blade throughout the coating process. The speed of the blade is typically the main factor affecting film thickness for given solution concentration and viscosity (typically increasing concentration and viscosity leads to thicker films).…”

Section: Casting Methodologymentioning

confidence: 99%

“…Slot-die coaters integrated into roll-to-roll systems have, however, important limitations, as they require large amounts of material and the complexity of the equipment makes it very exclusive. [22,23] Thickness gradients can be easily fabricated by blade coating [24] and indeed have been employed as a demonstration for the potential of gradients in the optimization of organic photovoltaics (OPV) and organic light emitting diodes (OLEDs) at laboratory scale. [24,25] The local evaluation of performance is typically done by using techniques such as light beam induced current (LBIC), micro-electroluminescence or lock-in thermography.…”

Section: Introductionmentioning

confidence: 99%

“…[22,23] Thickness gradients can be easily fabricated by blade coating [24] and indeed have been employed as a demonstration for the potential of gradients in the optimization of organic photovoltaics (OPV) and organic light emitting diodes (OLEDs) at laboratory scale. [24,25] The local evaluation of performance is typically done by using techniques such as light beam induced current (LBIC), micro-electroluminescence or lock-in thermography. [26] While these techniques are commonly employed for other types of studies, such as degradation studies, they can be equally suited for the inspection of samples intendedly fabricated with lateral inhomogeneities.…”

Section: Introductionmentioning

confidence: 99%

“…It is worth noting that there have been attempts to directly monitor the characteristics of 2D composition gradients [22,23] and some of them studied the combination of thickness and temperature effects, [27] or thickness gradient screening using discrete devices. [28,29] In this work, we advance a simple fabrication platform based on blade coating that enables the fabrication of thickness, composition, and morphology gradients. We then demonstrate its usefulness by preparing solar cells of three different systems with a composition gradient that reveals the optimum D:A blending ratio in a single substrate with minimal materials usage (<10 mg per material) and easy processing feasible with the existing infrastructure in most research laboratories in this field.…”

Section: Introductionmentioning

confidence: 99%

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High‐Throughput Multiparametric Screening of Solution Processed Bulk Heterojunction Solar Cells

Sánchez-Díaz

Rodríguez‐Martínez

Córcoles-Guija

et al. 2018

Adv Elect Materials

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(MDMO-PPV) or poly(3-hexylthiophene) (P3HT) combined with soluble fullerenes, [6,7] up to current PCE values exceeding 10% for several systems. [9][10][11][12][13] There is no specific fundamental limitation to organic materials that indicates that much higher values are not possible, and the number of potential candidates is nearly infinite. Indeed, the organic nature of the photoactive materials offers a myriad of possibilities to modify their chemical structure; for the case of conjugated polymers, there exists a vast assortment of combinations depending on the choice of moieties, the bridging atoms, the length and branching points of the alkyl side chains, and the molecular weight, to name but a few. Using search engines to inspect the literature, we estimate that in the last ten years ≈5000 organic conjugated materials have been tested in BHJ solar cells, albeit only a few tenths have been studied and optimized in depth. While applied quantum theory can help to select promising candidates, [14][15][16] the final performance often depends on a number of issues difficult to predict a priori, such as solubility, miscibility of compounds, tendency to crystallize, exact energy levels in the blend, etc. In practice, this means that for a given promising backbone, a family of systems need to be tested, including different side chains, molecular weights, donor:acceptor combinations, etc. [17] Within this large and uncharted spectrum of materials and processing variables, combinatorial screening methodologies are highly on demand to speed up their exploration while helping the technology to approach the theoretical Shockley-Queisser limit of >20% PCE. [18,19] From the engineering point of view, three main aspects must be addressed for the evaluation of a material system for BHJ solar cells, namely the active layer thickness, the donor-acceptor (D:A) blending ratio and the nanoscale morphology (typically controlled by deposition conditions, thermal annealing, and use of additives). Ideally, those three variables can be optimized separately and to some extent it is usually an acceptable approximation; however, the full potential of a novel active layer material requires for fine tuning of the preparation conditions that take into consideration the subtle interplay between them. [20] For instance, the optimum thickness is often found close to the first interference maximum, which is governed by the refractive index of the active layer; this, on the other hand, will be a function of the D:A ratio (fullerenes typically have higher refractive index than polymers) and the degree of crystallinity One of the major bottlenecks in the development of organic photovoltaics is the time needed to evaluate each material system. This time ranges from weeks to months if different variables such as blend composition, thickness, annealing, and additives are to be explored. In this study, the use of lateral gradients is proposed in order to evaluate the photovoltaic potential of a material system up to 50 times faster. A platform that c...

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Section: Casting Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

High‐Throughput Multiparametric Screening of Solution Processed Bulk Heterojunction Solar Cells

Sánchez-Díaz

Rodríguez‐Martínez

Córcoles-Guija

et al. 2018

Adv Elect Materials

View full text Add to dashboard Cite

show abstract

“…This observation is very much in accordance with literature where ∼100 nm thick absorber layers are often reported as optimum light harvesters for many highly-efficient photo-active polymers. 17 However, the optimum active layer thickness changes, when receiving light at oblique angles of incidence due to a different light propagation within the active layer. We therefore exemplify the white-light absorption profile for the 55 nm and 120 nm active layers in Figures 2(a) and 2(b respectively, for several angles of light incidence θ = 0 • , 30 • , 50 • and 70 • .…”

mentioning

confidence: 99%