Excitons in the perovskite

20 09 2014

There is an enormous variety of exotic properties in the methylammounium triiodideplumbate perovskite and related photovoltaic perovskites. A range of important questions are being discussed in meetings and papers. If there is consensus about one point among the main theorists of the field, it is that it is extremely unlikely that excitons persist for any significant time, due to dielectric screening. This view has been clearly expressed in the following papers

Frost, J. M.; Butler, K. T.; Brivio, F.; Hendon, C. H.; van Schilfgaarde, M.; Walsh, A. “Atomistic Origins of High-Performance in Hybrid Halide Perovskite Solar Cells”. Nano Letters 2014, 14, 2584-2590. (They state: It is clear that excitons will not play a significant role in the photovoltaic device physics.)

Menendez-Proupin, E.; Palacios, P.; Wahnon, P.; Conesa, J. C. “Self-consistent relativistic band structure of the CH3NH3PbI3 perovskite”. Physical Review B 2014, 90, 045207.

Analysis of Multivalley and Multibandgap Absorption and Enhancement of Free Carriers Related to Exciton Screening in Hybrid Perovskites, Jacky Even,  Laurent Pedesseau, and Claudine Katan, 2014, 118 (22), pp 11566–11572 (” Our analysis suggests exciton screening by collective orientational motion of the organic cations at room temperature, leading to almost free carriers.”)

For experimental results see

Yasuhiro Yamada , Toru Nakamura , Masaru Endo Atsushi Wakamiya , and Yoshihiko Kanemitsu Photocarrier Recombination Dynamics in Perovskite CH3NH3PbI3 for Solar Cell Applications J. Am. Chem. Soc., 2014, 136 (33), pp 11610–11613

Oxford nanoGe conferences 2014

16 09 2014

Two nanoGe Conferences celebrated in Oxford last week showed the extraordinary strength of the development of perovskite solar cells and the great general interest of quantum dots fundamental physics and solar cells.

International Conference of Fundamental Processes in Semiconductor Nanocrystals, 2014, Oxford, United Kingdom

International Conference Solution processed Semiconductor Solar Cells, 2014, Oxford, United Kingdom

The Conference on Solution processed semiconductor solar cells, being celebrated in Henry Snaith’s place, obtained massive fluence from perovskite solar cells people. Many presentations and discussions showed that the questions are being centered about relevant properties of the perovskite solar cell. After some period of puzzlement by the extraordinary novel characteristics, now everybody starts to present the questions and comes up with original explanations, that undoubtedly will be addressed in the the next months in the literature and in discussion forums. It is a nice generating moment in this field. The very fast development of materials was highlighted for example by Yang Yang presentation of the noted Science paper with efficiency over 19%. New interesting applications were suggested by Miyasaka exploiting the ferroic properties of the perovskite. Emilio Palomares came up with a happy metaphor about the current interest of the perovskite for new researchers with respect to the previous families of hybrid solar cells. The presence of quantum dot solar cells was less than in previous years but still showed innovative results especially about doping of nanocrystalas and formation of heterostructures. These questions as well as ultarfast phenomena and new applications (bio, LEDs) were also discussed in the conference on fundamentals by an impressive list of speakers and participants.

Both conferences benefited from the presence of Prof. Rudolph Marcus, Nobel laureate, that was very interested in the electron transfer problems and in the perovskite solar cells. It was wonderful and inspiring to talk to the great master.

14 09 11 SSSC14 invited speakers photo

Speakers and organizers SSSC14. Row 1: Tsutomu Miyasaka, Gary Hodes, Rudolph Marcus, Henry Snaith, Lioz Etgar, Arthur Nozik. Row 2: Seigo Ito, Nam-Gyu Park, David Mitzi, Alex Jen, Feliciano Giustino, Sam Stranks. Row 3: Satoshi Uchida, Iván Mora-Seró, Juan Bisquert, Emilio Palomares, Mercouri Kanatzidis, Arie Zaban.


nanoGe 14 Oxford


nanoGe 14 OxfordHenry Snaith, chair, showing their “first breakthrough” in perovskite solar cells

14 09 09 FQDots14 Marcus and Bisquert

Rudolph Marcus and JB

nanoGe14 Oxford Fun Qdots

Group photo FQDots14. Speakers and organizers Row 1: Sandy Ruhman, Zeger Hens , Laurens Siebbeles, Liberato Manna, Patanjali Kambhampati, Arthur Nozik, Daniël Vanmaekelbergh, Tom Gregorkiewicz, Rudolph Marcus, Efrat Lifshitz, Jonathan Owen, Dmitri Talapin. Row 2: Alf Mews , Christian Klinke, Arjan Houtepen, Ulrike Woggon, Todd Krauss, David Norris, Others: Horst Weller, Uri Banin, Alexander Eychmuller.

14 nanoGe Oxford

Efrat Lifshitz and Laurens Siebbels, chairs

nanoGe 14 Oxford

nanoGe staff Laura, Ramona, Paloma and friend Mario

Park Bisquert Palomares Oxford 14

Nam Gyu Park, JB and Emilio Palomares (insisting he is a doctor)


A comparison of evolution of solar cells and phone cells according to Emilio.

Perovskites solar cells, running too fast?

4 09 2014

Staggering increases in the performance of organic–inorganic perovskite solar cells have renewed the interest in these materials. However, further developments and the support from academic and industrial partners will hinge on the reporting of accurate efficiency values.


As pointed out by Grätzel, some open issues and pitfalls are now being debated in this community. Among these, the main concern revolves around the accuracy of the reported efficiency values. Specifically, hysteretic behaviour due to the strong dependence of the photocurrent on the voltage-scan conditions seems to be particularly pronounced in some perovskite solar cells. This has led to doubts about some reported power-conversion efficiency values, which may be altered by hysteresis-related artefacts.

See also


Slow Dynamic Processes in Lead Halide Perovskite Solar Cells. Characteristic Times and Hysteresis

HOPV 15 Conference in Rome

2 09 2014
If you don’t view the contents correctly, please click here
HOPV15 CONFERENCE Abstract submission opened
Hybrid and Organic Photovoltaics Conference
10-13 May 2015, Rome, Italy
Thrilling news in the perovskite area! Let us meet in the center of Rome on May 2015 for HOPV Conference.

Many of you know that HOPV (Hybrid and Organics Photovoltaic Conference) has been consolidated since 2009 as a unique forum for the advances in hybrid and organic photovoltaics. Now the HOPV15 Conference chairs, Filippo de Angelis and Mike McGehee, kindly invite you to present your latest research and participate in a major event in Rome, 10-13 May 2014. Of course the generous progress of perovskite solar cells will form a key part of the conference. But let’s not forget the basics. The research continues very promisingly in a variety of topics that will have a balanced presence in the conference, including perovskite and quantum dot solar cells, dye-sensitized solar cells, small molecular organic solar cells, hybrid organic-inorganic and nanostructured devices, bulk heterojunction polymer solar cells, and related field as solar fuel production catalysts and devices.

The conference format is a full three days, multiple symposia meeting, with outstanding figures of the field as keynotes and invited speakers, and with also room for plenty of contributed talks by participant scientists and unlimited poster presentation. The meeting gathered 620 participants and 20 companies of the field in 2014. In 2015 the conference unique setting in the center of Rome will provide an excellent opportunity for updates, major announcements of progress, and plenty of discussions. And do not forget the legendary HOPV parties. Next year we will celebrate that we meet all colleagues and friends having a social dinner in an amazing Barroque Palace.

Conference chairs:
Filippo De Angelis.
ISTM-CNR Perugia, Italy
Michael McGehee
Stanford School of Engineering, USA
 Conference Dinner
Wednesday night features the Social Dinner at Palazzo Brancaccio. Be sure to book your ticket during registration and meet new people, or renew old friendships or simply enjoy yourselves.
High-ranking invited speakers providing details about the major revolution to the field of organic-inorganic photovoltaics for an inspiring conference.
 Confirmed Keynote Speakers
Michael Grätzel. EPFL

Martin Green. University of New South Wales

Daniel Nocera. Harvard University

 Confirmed Invited Speakers
Hironori Arakawa. Tokyo University of Science

Thomas Bein. Department of Chemistry University of Munich

David Cahen. Weizmann Institute of Science

James Durrant. Imperial College London

Jacky Even. Institut National des Sciences Appliquées de Renne

Germà Garcia Belmonte. Universitat Jaume I

Joseph Hupp. Northwestern University

Antoine Kahn. Princeton University

Prashant V. Kamat. University of Notre Dame

Mercouri G. Kanatzidis. Northwestern University

Jaejung Ko. Korea University

Guglielmo Lanzani. Istituto Italiano di Tecnologia

Jenny Nelson. Imperial College London

Thuc-Quyen Nguyen. University of California

Nam-Gyu Park. Sungkyunkwan University

Andrew Rappe. University of Pennsylvania

Alberto Salleo. Stanford University

Henry J. Snaith. Department of Physics, University of Oxford

 Oral contributions
In addition, in the field of organic-inorganic photovoltaics, 96 high level selected oral contributions will take part of this leading photovoltaic community.

Please register as soon as possible in order to benefit from the early registration fees of the forthcoming 7th edition of the Hybrid and Organic Photovoltaics to be held in Rome, from 10th to 13thMay 2015. Submit your abstract for oral presentation or poster contribution at the one of the most imperative conference in transformative photovoltaics technologies. Online abstract submission is now opened.

More details athttp://www.nanoge.org/HOPV15/info_abstract.php

 My Meeting Checklist
 Want to exhibit or be a sponsor?
We provide you with an excellent opportunity to market your instruments at the HOPV 2015 conference (http://www.nanoge.org/HOPV15/index.php) where you will meet more than 600 scientists who work exclusively on solar energy projects. We encourage you to contact us for more details at hopv15@nanoge.org

Capacitive currents and hysteresis in solar cells

25 08 2014

14 08 25 Capacitive currents in solar cells

This is part of my presentation at

Gordon Research Conference: Electron Donor-Acceptor Interactions, Newport, USA, August 3-8, 2014

It is a short illustration of the capacitive currents that may be very significant for perovskite solar cells.

Recently Hui-Seon Kim and Nam-Gyu Park have argued similarly in

Parameters Affecting IV Hysteresis of CH3NH3PbI3 Perovskite Solar Cells: Effects of Perovskite Crystal Size and Mesoporous TiO2 Layer

J. Phys. Chem. Lett., 2014, 5, pp 2927–2934

Best Practices for Reporting on Heterogeneous Photocatalysis

20 08 2014

Best Practices for Reporting on Heterogeneous Photocatalysis


Jillian M. Buriak (Editor-in-Chief, Chemistry of Materials) ,
University of Alberta
Prashant V. Kamat (Deputy Editor, The Journal of Physical Chemistry Letters) ,
University of Notre Dame
Kirk S. Schanze (Editor-in-Chief, ACS Applied Materials & Interfaces)
University of Florida
ACS Appl. Mater. Interfaces, 2014, 6 (15), pp 11815–11816
DOI: 10.1021/am504389z

Mariam Mirzakhani wins the Field Medal of Mathematics

13 08 2014

A professor of mathematics at Stanford University in California, iranian-native Mariam Mirzakhani won the 2014 Field Medal of Mathematics and becomes the first woman winner. The panel appreciated the Mirzakhani’s innovative contributions in the dynamics and geometry of Riemann surfaces and their moduli spaces.

The Fields Medal is awarded every 4 years to at most 4 mathematicians under 40 years. It is regarded as the highest honor a mathematician can receive.

more information



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