Detection and role of trace impurities in high-performance organic solar cells

Nikiforov, Maxim P.; Lai, Barry; Chen, Wei; Chen, Si; Schaller, Richard D.; Strzalka, Joseph; Mäser, J.; Darling, Seth B.

doi:10.1039/c3ee40556g

Cited by 168 publications

(163 citation statements)

References 34 publications

Supporting

Mentioning

158

Contrasting

Order By: Relevance

“…Several studies have previously demonstrated that P3HT molecular weight variations in the range of 10-20 kg mol À 1 do not significantly affect the morphology and device performance of the pristine polymer or P3HT/PCBM-based photovoltaics [22][23][24] . In addition, the Ni residues in the highly pure protonated and deuterated P3HT polymers synthesized for this study were measured by inductively coupled plasma mass spectroscopy to be less than 0.0014 wt.%, which is 50 times smaller than the threshold concentration of metal impurities for noticeable effects on device performance in previous studies [25][26][27] . Therefore, we exclude the impact of the molecular weight difference and metal residues on the measured optoelectronic properties between the deuterated and protonated P3HT polymers in this work.…”

Section: Resultsmentioning

confidence: 99%

The isotopic effects of deuteration on optoelectronic properties of conducting polymers

et al. 2014

Self Cite

View full text Add to dashboard Cite

The attractive optoelectronic properties of conducting polymers depend sensitively upon intra-and inter-polymer chain interactions, and therefore new methods to manipulate these interactions are continually being pursued. Here, we report a study of the isotopic effects of deuterium substitution on the structure, morphology and optoelectronic properties of regioregular poly(3-hexylthiophene)s with an approach that combines the synthesis of deuterated materials, optoelectronic properties measurements, theoretical simulation and neutron scattering. Selective substitutions of deuterium on the backbone or side-chains of poly(3-hexylthiophene)s result in distinct optoelectronic responses in poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) photovoltaics. Specifically, the weak non-covalent intermolecular interactions induced by the main-chain deuteration are shown to change the film crystallinity and morphology of the active layer, consequently reducing the short-circuit current. However, side-chain deuteration does not significantly modify the film morphology but causes a decreased electronic coupling, the formation of a charge transfer state, and increased electron-phonon coupling, leading to a remarkable reduction in the open circuit voltage.

show abstract

Section: Resultsmentioning

confidence: 99%

The isotopic effects of deuteration on optoelectronic properties of conducting polymers

et al. 2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…In practice, the impedance spectroscopy data (see Fig. S1) indicate the presence of high density of defect states acting as p-type dopants in the semiconductor (27)(28)(29)(30). Under solar illumination, these defects are filled by photoinduced electrons, and they form a space-charge region (with corresponding nonlinear bending of the energy band diagram) near the organic low work function metal (27) (the solid lines of Fig.…”

Section: Interpretation Of the Key Experimentsmentioning

confidence: 99%

Collection-limited theory interprets the extraordinary response of single semiconductor organic solar cells

Ray

Baradwaj

Khan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The bulk heterojunction (BHJ) organic photovoltaic (OPV) architecture has dominated the literature due to its ability to be implemented in devices with relatively high efficiency values. However, a simpler device architecture based on a single organic semiconductor (SS-OPV) offers several advantages: it obviates the need to control the highly system-dependent nanoscale BHJ morphology, and therefore, would allow the use of broader range of organic semiconductors. Unfortunately, the photocurrent in standard SS-OPV devices is typically very low, which generally is attributed to inefficient charge separation of the photogenerated excitons. Here we show that the short-circuit current density from SS-OPV devices can be enhanced significantly (∼100-fold) through the use of inverted device configurations, relative to a standard OPV device architecture. This result suggests that charge generation may not be the performance bottleneck in OPV device operation. Instead, poor charge collection, caused by defect-induced electric field screening, is most likely the primary performance bottleneck in regular-geometry SS-OPV cells. We justify this hypothesis by: (i) detailed numerical simulations, (ii) electrical characterization experiments of functional SS-OPV devices using multiple polymers as active layer materials, and (iii) impedance spectroscopy measurements. Furthermore, we show that the collection-limited photocurrent theory consistently interprets typical characteristics of regular SS-OPV devices. These insights should encourage the design and OPV implementation of high-purity, high-mobility polymers, and other soft materials that have shown promise in organic field-effect transistor applications, but have not performed well in BHJ OPV devices, wherein they adopt less-than-ideal nanostructures when blended with electron-accepting materials.T he photovoltaic properties of semiconducting polymers arranged in a simple metal-polymer-metal sandwich structure were first demonstrated in 1993 by several groups (1-3). The efficiency values of these early photovoltaic (PV) cells were minuscule mainly because of the poor short-circuit current densities (J sc ∼10 μA cm −2 ) under standard 1 sun illumination. By definition,where J ph ðV Þ is the voltage-dependent photocurrent, η ex is the exciton diffusion-dissociation (or free-charge generation) efficiency, η C is the charge (free-carrier) collection efficiency, and J max is the maximum current density obtained by integrating absorption spectra (J max ∼ 10 − 20 mA cm −2 for typical semi-conducting polymers). The difference between J sc and J max was attributed to an inefficient η ex (<0.1%) arising from ultrashort exciton diffusion lengths (∼10-15 nm) in semiconducting polymers and was eventually interpreted by Onsager's theory of geminate pair recombination (4-6). This classical interpretation assumes, on the other hand, that η C ∼ 100%. To improve η ex , Heeger and co-workers (7) and Holmes and coworkers (8) introduced the concept of bulk heterojunction (BHJ) devices in 1995. Her...

show abstract

“…The side products and catalyst residues need to be removed via purification methods like column chromatography or sublimation, which are time-consuming and expensive. [204,205] This generally leads to commercial prices exceeding $200 g −1 , and thus reaching lower module target costs is challenging.…”

Section: Long-term Viability: Stability and Sustainabilitymentioning

confidence: 99%

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Petrus

Schlipf

Cheng

et al. 2017

Advanced Energy Materials

312

201

View full text Add to dashboard Cite

following statement: These materials can be processed from solution and yet exhibit optoelectronic materials properties described in classic solid-state physics textbooks. This unprecedented combination has led to photovoltaic devices that can be processed at room temperature and achieve performance levels similar to industry giant polycrystalline silicon, from a starting point of 3.8% in 2009. [1][2][3][4] The first light-emitting electrochemical cells [5] and diodes [6][7][8] have also been introduced recently, leading to tunable light emission spectra and internal quantum efficiencies exceeding 15%.The road towards these achievements has been marked by a constant improvement of perovskite deposition techniques fueled by our increasing understanding of the crystallization processes. The choice of deposition technique, either from solution or vapor, and the composition and order in which precursor species are applied has a great influence on the crystallization kinetics. Here, one can distinguish one-step methods where the perovskite is formed from a precursor mixture dissolved in a common solution, and two-step methods where the inorganic compound is deposited first and transformed to the perovskite phase later by addition of the organic constituents. [9][10][11] Furthermore, many parameters during processing can have an effect on the crystallization mechanism and consequently on film morphology, such as the choice of solvents, concentrations and processing additives that are often not incorporated into the final product. [11][12][13] We discuss this aspect in Section 2, where we focus our attention on the most commonly employed solution-based techniques. Additionally, as for any new technology trying to displace an incumbent technology, higher efficiencies, lower costs, reproducibility, stability, and sustainability are paramount. In particular, reproducibility has been a major challenge in perovskite solar cells from the beginning: small variations in morphology, like crystal size, film roughness, and pinholes can have detrimental effects on photovoltaic performance. [14] On the other hand, current-voltage measurements often showed a hysteresis that is rarely seen in other photovoltaic technologies. [15] These topics are highlighted in Sections 3 and 4. Finally, in Section 5 we discuss the framework for market introduction, such as cost reduction by choosing low-cost charge transport layers, or how the lifetime of perovskite absorbers can be extended by the choice of materials composition.Hybrid metal halide perovskites have become one of the hottest topics in optoelectronic materials research in recent years. Not only have they surpassed everyone's expectations and achieved similar performance as tried and true polycrystalline silicon photovoltaic devices, but they are also finding applications in a variety of different fields, including lighting. The main advantages of hybrid metal halide perovskites are simple processability, compatible with large-scale solution processing such as roll-to-roll printing, a...

show abstract

Detection and role of trace impurities in high-performance organic solar cells

Cited by 168 publications

References 34 publications

The isotopic effects of deuteration on optoelectronic properties of conducting polymers

The isotopic effects of deuteration on optoelectronic properties of conducting polymers

Collection-limited theory interprets the extraordinary response of single semiconductor organic solar cells

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Contact Info

Product

Resources

About