Small molecule tandem cells

The next step was the use of solution processed charge transport layers in the recombination contact of polymer solar cells. In 2007, Gilot et al showed that ZnO nanoparticles processed from acetone can be covered with a layer of pH-neutral PEDOTrPSS spincoated from a dispersion in water to fabricate a ZnO/PEDOT PSS recombination layer that is transparent to light and makes an almost loss-less recombination layer for tandem and triple junction cells. This approach bears similarity to the p- and n-doped wide bandgap transport layers developed for evaporated small molecule tandem cells. The ZnO/PEDOT PSS recombination contact was initially employed in... 

These approaches optimize the tandem cell by varying the thickness of the active layers. It is also possible to balance the subcells by varying the thickness of charge transport layers. These can act as optical spacers to adjust the electrical optical field in the layer stack such that it maximizes in the photoactive layers. This approach is particularly useful for vacuum processed small molecule tandem cells where the low charge mobility dictates the use of thin photoactive layers of 20-50 nm." ... 

Schueppel R, Timmreck R, Allinger N, Mueller T, Fumo M, Uhrich C, Leo K, Riede M (2010) Controlled current matching in small molecule organic tandem solar cells using doped spacer layers. J Appl Phys 107 6... 

In both tandem-in-space and tandem-in-time instruments, the most common experiment is for the first analyzer to select specific ions from the total ion beam arriving from the ion source. Next, the selected ions undergo collision-induced dissociation (CID) in a pressurized cell followed by the analysis of the product ions in the second analyzer. In tandem-in-time the same analyzer is used for both scans, but at different times. The resulting product ion spectra (or precursor and neutral loss spectra in other forms of MS/MS analysis) provide vital structural information for the identification of small molecules (such as drug metabolites) as well as complex biomolecules. Selected reaction monitoring (SRM), another mode of MS/MS operation, provides highly specific and sensitive quantification of target analytes. 

Che X, Xiao X, Zimmerman JD, Fan D, Forrest SR (2014) High-effieiency, vacuum-deposited, small-molecule organic tandem and triple-junction photovoltaic cells. Adv Energy Mater 4 1400568... 

Very recently, several new classes of solution processible small molecule donors with favorable optical and electronic properties have been reported for use in OPV devices. When coupled with fullerene electron acceptors, such as [6,6]-phenyl-C7i-butyric acid methyl ester (PCy BM), solution processible small molecule based solar cells have achieved record PCEs over 8% for single layers devices and 10% for tandem cells. This chapter provides an overview of several important classes of solution processible small molecules used as donor materials in high performance OPV devices. For greater details on materials and devices, the reader is referred to several excellent reviews by Meerholz, Nguyen, Bauerle, Zhan, and Roncali. ... 

Figure 5.32 Structure of an oligothiophene-based small molecule with 3-ethyl-rhodanine end-capping units and a 2-D BDT core, used as a donor in both single and tandem junction SM-BHJ solar cells.

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