Quantum dot solar cells with 8% efficiency

17 04 2015

Quantum dot layer solar cells have recently appeared in Tables with high (9%) efficiency. But here we show that quantum dot solar cells with TiO2 framework are also progressing rapidly and now show a certified 8% efficiency.

Furthermore this paper incorporates Enrique Canovas and Mischa Bonn to the previous team and we provide new fundamental insights with respect to the common image of injection and charge separation in the quantum dot solar cells

Boosting Power Conversion Efficiencies of Quantum-Dot-Sensitized Solar Cells Beyond 8% by Recombination Control

Ke Zhao, Zhenxiao Pan, Iván Mora-Seró, Enrique Cánovas, Hai Wang, Ya Song, Xueqing Gong, Jin Wang, Mischa Bonn, Juan Bisquert§, and Xinhua Zhong*
J. Am. Chem. Soc., Article ASAP
DOI: 10.1021/jacs.5b01946
Publication Date (Web): April 10, 2015
Copyright © 2015 American Chemical Society
ja-2015-019465_0007
At present, quantum-dot-sensitized solar cells (QDSCs) still exhibit moderate power conversion efficiency (with record efficiency of 6–7%), limited primarily by charge recombination. Therefore, suppressing recombination processes is a mandatory requirement to boost the performance of QDSCs. Herein, we demonstrate the ability of a novel sequential inorganic ZnS/SiO2 double layer treatment onto the QD-sensitized photoanode for strongly inhibiting interfacial recombination processes in QDSCs while providing improved cell stability. Theoretical modeling and impedance spectroscopy reveal that the combined ZnS/SiO2treatment reduces interfacial recombination and increases charge collection efficiency when compared with conventional ZnS treatment alone. In line with those results, subpicosecond THz spectroscopy demonstrates that while QD to TiO2 electron-transfer rates and yields are insensitive to inorganic photoanode overcoating, back recombination at the oxide surface is strongly suppressed by subsequent inorganic treatments. By exploiting this approach, CdSexTe1–x QDSCs exhibit a certified record efficiency of 8.21% (8.55% for a champion cell), an improvement of 20% over the previous record high efficiency of 6.8%, together with an additional beneficial effect of improved cell stability.




A Solid State Physics Perspective on Hybrid Perovskite Semiconductors

5 04 2015

The Journal of Physical Chemistry C is presenting a series of Feature Articles by key scientists about the fundamental properties of Hybrid Organic-Inorganic Halide Perovskites.

A Solid State Physics Perspective on Hybrid Perovskite Semiconductors

Jacky Even , Laurent Pedesseau , Claudine Katan , Mikaël Kepenekian , Jean-Sébastien Lauret ,Daniel Sapori , and Emmanuelle Deleporte
J. Phys. Chem. C,
DOI: 10.1021/acs.jpcc.5b00695

In this review we examine recent theoretical investigations on 2D and 3D hybrid perovskites (HOP) that combine classical solid-state physics concepts and density functional theory (DFT) simulations as a tool for studying their optoelectronic properties. Such an approach allows one to define a new class of semiconductors, where the pseudocubic high temperature perovskite structure plays a central role. Bloch states and k.p Hamiltonians yield new insight into the influence of lattice distortions, including loss of inversion symmetry, as well as spin-orbit coupling. Electronic band folding and degeneracy, effective masses and optical absorption are analyzed. Concepts of Bloch and envelope functions, as well as confinement potential are discussed in the context of layered HOP and 3D HOP heterostructures. Screening and dielectric confinements are important for room temperature optical properties of 3D and layered HOP, respectively. Non-radiative Auger effects are analyzed for the first time close to the electronic band gap of 3D hybrid perovskites.





The risks of speeding up publication of scientific papers

31 03 2015

The process of publication of scientific papers relies on the prestige of journals that govern the peer review process. In the era in which everyone is multiply connected the editorial process is evidently affected and many changes are likely to happen in the coming years. Journals fight fiercely for getting the good papers, which increase their impact factors, as authors are eager to publish in high impact factor journals, which determines their career promotion and project winning possibilities.

Now the question is, if increasingly fast and easier pathways to publication can have the detrimental effect to increase the mediocrity of scientific production. Recently JPCL editors Kamat and Schatz commented this point in an editorial http://pubs.acs.org/doi/full/10.1021/acs.jpclett.5b00286 that highlights the difference between Reports and Scientific Journal. Later on, concerns were raised when a Nature Journal put in place a faster publication track–for a fee. Some people has commented that in the final limit one would have the paper accepted before submission. See the details of this story.





Global Trends in Renewable Energy Investment 2015

31 03 2015

Renewables Re-energized: Green Energy Investments Worldwide Surge 17% to $270 Billion in 2014

According to  UNEP’s 9th “Global Trends in Renewable Energy Investment 2015″, prepared by the Frankfurt School-UNEP Collaborating Centre for Climate & Sustainable Energy Finance and Bloomberg New Energy Finance, the United Nations Environment Programme (UNEP) and Bloomberg New Energy Finance — the past year brought a rebound of green energy investments worldwide with a surge of a solid 17% to $270 Billion. Brushing aside the challenge of sharply lower crude oil prices this sudden increase reveresed the investment dip of the past two years and was mainly driven by investments in solar and wind energy.

see the reports here





Bous a la mar

24 03 2015

Bous a la mar en Denia, late 70s

bous





Smart girl scientists in Iran

13 03 2015

60% of Iran scientists are women. Competent, smart, ambitious. They travel abroad and know the modern mind. But will they find a ceiling if going up in the ranks?

Several lady scientists and JB at Asian Nano Forum Congress 2015, Kish Island, Iran

Several solar cell scientists (Raheleh Mohammadpour, Leila Shooshtari, two ladies, Sara Rahimnejad and JB) at Asian Nano Forum Congress 2015, Kish Island, Iran

 





Best Practices in Perovskite Solar Cell Efficiency Measurements.

6 03 2015
Jeffrey A. Christians, Joseph S. Manser, and Prashant V. Kamat
J. Phys. Chem. Lett. 2015, 6, 852–857
DOI: 10.1021/acs.jpclett.5b00289

This Viewpoint brings to light some of the issues pertaining to perovskite solar cells and provides the field with best practices for measuring and reporting perovskite solar cell performance.







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