Diffusion and recombination in nanostructured materials

25 06 2013

Many years back the measurement of diffusion coefficient and lifetime of dye-sensitized solar cells consistently showed that the parameters displayed a strong dependence with the voltage. Ideas explaining such behaviour date back to the seminal work of A. Rose in 1960s, but a consistent framework had not been formulated to account for the results of small perturbation techniques, that really allow a good definition of the parameters, since a kinetic constant can be uniquely associated to a position of the Fermi level. Many ideas were used in several works, such as the classical definition of the chemical diffusion coefficient, thermodynamic factor, and the quasistatic approximation that facilitates the integration of traps in the scheme. It emerged that a neat distinction can be made between single particle quantities like the jump diffusion coefficient and collective quantities like the chemical diffusion coefficient. But the lifetime took more time to clarify, since even the free carrier lifetime usually displays a dependence on Fermi level due to nonlinear recombination. Now in cooperation with Mehdi Ansari-Rad and Juan Antonio Anta a mor general framework has been developed that summarizes the previous theory and furthermore includes the lifetime in the scheme, consistently. I think this work provides a very complete theory for the interpretation of measurements of solar cells using disordered materials.

J. Phys. Chem. C (Feature Article)
DOI: 10.1021/jp403232b
Mehdi Ansari-Rad and JB

Mehdi Ansari-Rad and JB at UJI

Patents and abstract ideas

13 06 2013





No. 12–398. Argued April 15, 2013—Decided June 13, 2013

Held: A naturally occurring DNA segment is a product of nature and not patent eligible merely because it has been isolated, but cDNA is patent eligible because it is not naturally occurring. Pp. 10–18.

(a) The Patent Act permits patents to be issued to “[w]hoever in-vents or discovers any new and useful . . . composition of matter,” §101, but “laws of nature, natural phenomena, and abstract ideas” “ ‘are basic tools of scientific and technological work’ ” that lie beyond the domain of patent protection, Mayo, supra, at ___. The rule against patents on naturally occurring things has limits, however. Patent protection strikes a delicate balance between creating “incen-tives that lead to creation, invention, and discovery” and “imped[ing] the flow of information that might permit, indeed spur, invention.”

b) Myriad’s DNA claim falls within the law of nature exception. Myriad’s principal contribution was uncovering the precise location and genetic sequence of the BRCA1 and BRCA2 genes. Diamond v. Chakrabarty, 447 U. S. 303, is central to the patent-eligibility inquiry whether such action was new “with markedly different characteris-tics from any found in nature,” id., at 310. Myriad did not create or alter either the genetic information encoded in the BCRA1 and BCRA2 genes or the genetic structure of the DNA. It found an im-portant and useful gene, but groundbreaking, innovative, or even brilliant discovery does not by itself satisfy the §101 inquiry. See Funk Brothers Seed Co. v. Kalo Inoculant Co., 333 U. S. 127. Finding the location of the BRCA1 and BRCA2 genes does not render the genes patent eligible “new . . . composition[s] of matter,” §101. Myri-ad’s patent descriptions highlight the problem with its claims: They detail the extensive process of discovery, but extensive effort alone is insufficient to satisfy §101’s demands. Myriad’s claims are not saved by the fact that isolating DNA from the human genome severs the chemical bonds that bind gene molecules together. The claims are not expressed in terms of chemical composition, nor do they rely on the chemical changes resulting from the isolation of a particular DNA section. Instead, they focus on the genetic information encoded in the BRCA1 and BRCA2 genes. Finally, Myriad argues that the Patent and Trademark Office’s past practice of awarding gene patents is en-titled to deference, citing J. E. M. Ag Supply, Inc. v. Pioneer Hi-Bred Int’l, Inc., 534 U. S. 124, a case where Congress had endorsed a PTO practice in subsequent legislation. There has been no such endorse-ment here, and the United States argued in the Federal Circuit and in this Court that isolated DNA was not patent eligible under §101. Pp. 12–16.