EES Blog

In their recent EES Perspective, Odobel, Pellegrin and Warnan provide an extensive and balanced overview of various bio-inspired systems that utilize the antenna effect to improve light absorption in both liquid and solid state dye-sensitised solar cells (DSCs).

In Nature, the optimization of light capture occurs via special molecular units, called light harvesting antennas. These light harvesting antenna collect the incident photons with several different pigments and funnel them by efficient energy transfer to a single molecular unit, which triggers a photo-induced electron transfer chain.

Molecular dyes display discrete absorption bands making it difficult to achieve panchromatic absorption with a single dye. By using a combination of different dyes with complementary absorption spectra in absorbing units, mimicking the light harvesting antenna of natural photosynthetic systems, it is possible to extend the absorbance of DSCs.

As light absorption is the primary step in any photovoltaic device, panchromatic light collection is fundamental to maximize the efficiency of a solar cell.  A lot of work has been performed in the last few years on the possibility of improving the light collecting efficiency of DSCs by exploiting the antenna effect. This excellent perspective highlights how new and innovative multi-chromophoric sensitizers can effectively broaden and enhance the absorption cross-section enabling higher photocurrent density in solar cells.

For an up-do-date picture of this exciting field, read this perspective article today:

Bio-inspired artificial light-harvesting antennas to enhance solar energy capture in dye-sensitized solar cells
Fabrice Odobel, Yann Pellegrin and Julien Warnan
DOI: 10.1039/C3EE24229C

In their recent EES article, scientists from Taiwan, Spain and Switzerland illustrate a practical strategy to achieve highly efficient dye-sensitized solar cells (DSSCs). They show that the short circuit current of a DSSC can be increased by the addition of fused aromatic substituents onto the polypyridyl Ru (II) sensitizers.

The extended pi-conjugation introduced by the aromatic substituents (isoquinolinyl groups) improves the optical absorptivity of this novel class of Ru(II) sensitizers, compared with the parent sensitizer TFRS-1. The DSSC incorporated with these dyes achieved over double-digit efficiencies.

Furthermore, the authors found that the addition of t-butyl substituents to the ancillary chelates results in longer device electron life-times. They were also able to optimize the cell by deprotonating the carboxy anchors during absorption.

Read this HOT EES article today:

Harnessing the open-circuit voltage via a new series of Ru(II) sensitizers bearing (iso-)quinolinyl pyrazolate ancillaries
Kuan-Lin Wu, Wan-Ping Ku, John N. Clifford, Emilio Palomares, Shu-Te Ho, Yun Chi, Shih-Hung Liu, Pi-Tai Chou, Mohammad K. Nazeeruddin and Michael Grätzel
DOI: 10.1039/C2EE23988D

Energy & Environmental Science Advisory Board member Dr Henry Snaith, an expert in the field of photovoltaic devices, has chosen a selection of excellent articles recently published in this area in Energy & Environmental Science.

You can read these articles for free for a limited period by clicking on the links below.

With an Impact Factor of 9.61 and ranked #1 in its field, Energy & Environmental Science is the ideal place to publish your research.

On behalf of Editor-in-Chief Nate Lewis (Caltech) we invite you to submit your best work to Energy & Environmental Science.

Read Dr Snaith’s Editor’s choice selection today:

Influence of the dye molecular structure on the TiO2 conduction band in dye-sensitized solar cells: disentangling charge transfer and electrostatic effects
Enrico Ronca, Mariachiara Pastore, Leonardo Belpassi, Francesco Tarantelli and Filippo De Angelis
DOI: 10.1039/C2EE23170K

A novel high-performance photovoltaic–thermoelectric hybrid device
Ning Wang, Li Han, Hongcai He, Nam-Hee Park and Kunihito Koumoto
DOI: 10.1039/C1EE01646F

Design and coupling of multifunctional TiO2 nanotube photonic crystal to nanocrystalline titania layer as semi-transparent photoanode for dye-sensitized solar cell
Min Guo, Keyu Xie, Jia Lin, Zehui Yong, Cho Tung Yip, Limin Zhou, Yu Wang and Haitao Huang
DOI: 10.1039/C2EE22854H

High-efficiency dye-sensitized solar cell with a novel co-adsorbent
Liyuan Han, Ashraful Islam, Han Chen, Chandrasekharam Malapaka, Barreddi Chiranjeevi, Shufang Zhang, Xudong Yang and Masatoshi Yanagida
DOI: 10.1039/C2EE03418B

Solar cells with one-day energy payback for the factories of the future
Nieves Espinosa, Markus Hösel, Dechan Angmo and Frederik C. Krebs
DOI: 10.1039/C1EE02728J

An 8.2% efficient solution-processed CuInSe2 solar cell based on multiphase CuInSe2 nanoparticles
Sunho Jeong, Byung-Seok Lee, SeJin Ahn, KyungHoon Yoon, Yeong-Hui Seo, Youngmin Choi and Beyong-Hwan Ryu
DOI: 10.1039/C2EE21269B

Semi-transparent polymer solar cells with 6% PCE, 25% average visible transmittance and a color rendering index close to 100 for power generating window applications
Kung-Shih Chen, José-Francisco Salinas, Hin-Lap Yip, Lijun Huo, Jianhui Hou and Alex K.-Y. Jen
DOI: 10.1039/C2EE22623E

Low band gap liquid-processed CZTSe solar cell with 10.1% efficiency
Santanu Bag, Oki Gunawan, Tayfun Gokmen, Yu Zhu, Teodor K. Todorov and David B. Mitzi
DOI: 10.1039/C2EE00056C

Charge generation and energy transfer in hybrid polymer/infrared quantum dot solar cells
Elisabeth Strein, Adam Colbert, Selvam Subramaniyan, Hirokazu Nagaoka, Cody W. Schlenker, Eric Janke, Samson A. Jenekhe and David S. Ginger
DOI: 10.1039/C2EE24175G

High performance polymeric charge recombination layer for organic tandem solar cells
Yinhua Zhou, Canek Fuentes-Hernandez, Jae Won Shim, Talha M. Khan and Bernard Kippelen
DOI: 10.1039/C2EE23294D

Take a look at our exciting themed collection on solar energy online.

In their recent EES review, He, Qiu and Lin provide a very interesting overview of polymer thermoelectric materials. They highlight recent advances in the preparation, modification and optimization of these materials and focus on current strategies to minimize thermal conductivity and maximize power factor.

Polymer thermoelectric materials are an emerging class of materials that have not yet received the recognition of their inorganic and intermetallic counterparts. However, their development is rapidly progressing towards efficient materials for all kinds of applications.  Polymers have many intrinsic advantages, such as low thermal conductivity, that make them ideal for fabricating high performance, light-weight and flexible thermoelectric modules.

Read the detail in this interesting EES review:

Towards high-performance polymer-based thermoelectric materials
Ming He, Feng Qiu and Zhiqun Lin
DOI: 10.1039/C3EE24193A

In a recent EES communication, scientists have developed a novel redox shuffle that can provide efficient and long-lasting overcharge protection for lithium-ion batteries.

This exciting article has been featured in C&EN News. Read the C&EN article here…

Although statistically very safe and reliable, there have been some exceptional incidents involving lithium ion batteries catching fire. Overcharging a lithium ion battery can cause the cathode can react with and decompose the electrolyte solution, generating heat and reactive gases. Incorporation of overcharge prevention into lithium-ion batteries is, therefore, key to improving their safety. Redox shuttle molecules, that can be reversibly oxidized and reduced at specific potentials, provide an effective and economic method to prevent overcharge abuse for lithium-ion batteries.

Read this article in EES today:

Molecular engineering towards safer lithium-ion batteries: a highly stable and compatible redox shuttle for overcharge protection
Lu Zhang, Zhengcheng Zhang, Paul C. Redfern, Larry A. Curtiss and Khalil Amine
DOI: 10.1039/C2EE21977H

Authors from Harvard University and Korea University discuss the science and technology of nanowire-based photovoltaics in their recent EES review.

They review the unique benefits and remaining challenges, such as scaling, of nanowires for photovoltaics and the progress towards understanding and optimizing the electrical and optical performance of nanowire devices. Advances in the synthesis, characterisation and control of the unique optical properties of nanowires along with their assembly and scaling into diverse arrays are presented.

Nanowires have emerged as one promising platform to explore next-generation solar cells that can operate more efficiently and be produced at a lower cost. Their small dimensions allow for efficient charge separation and light absorption properties different to bulk materials. The high cost of photovoltaics is currently a major limiting factor to the widespread use of solar power.

Read this review today:

Semiconductor nanowires: a platform for exploring limits and concepts for nano-enabled solar cells
Thomas J. Kempa, Robert W. Day, Sun-Kyung Kim, Hong-Gyu Park and Charles M. Lieber
DOI: 10.1039/C3EE24182C

Dye-based solar cells that use photonic crystals to boost efficiency have been developed, and could find application in the production of photovoltaic windows.

A team of researchers from Spain has studied how the current produced from a photonic-crystal dye-based solar cell (PC-DSC) varies according to the angle at which light strikes it. They found it was possible to fine tune the design of the cell’s photonic-crystal back mirror so as to minimize efficiency losses associated with light approaching from an angle.

Dye-based solar cells often employ back mirrors, which reflect light back into the device that would otherwise pass straight through it, thereby increasing efficiency. Designing these back mirrors from photonic crystals ensures the solar cells remain optically transparent, making the technology idea for the development of light-sensitive window panes.

Read this HOT Energy & Environmental Science article today:

Angular response of photonic crystal based dye sensitized solar cells
Carmen Lopez-Lopez , Silvia Colodrero , Mauricio Ernesto Calvo and Hernan Miguez
DOI: 10.1039/C3EE23609A

Scientists in Korea have made a flexible hybrid plastic film, embedded with silver nanowires, which can be used as an electrode for flexible solar cells.

Silver nanowires were embedded in the surface of a glass-fabric reinforced transparent composite film to form a substrate with excellent opto-electrical properties, mechanical flexibility and, unlike typical plastic substrates, good thermal stability. An inverted polymer solar cell with an efficiency of 5.9% was made based on these hybrid electrodes, comparable to the efficiency of the more conventional devices based on indium tin oxide/glass.

Read this HOT article today:

High-performance hybrid plastic films: a robust electrode platform for thin-film optoelectronics
Jungho Jin, Jaemin Lee, Seonju Jeong, SeungCheol Yang, Ji-Hoon Ko, Hyeon-Gyun Im, Se-Woong Baek, Jung-Yong Lee and Byeong-Soo Bae
DOI: 10.1039/C3EE24306K

Scientists in South Korea have made a conducting polymer as part of a thin-film thermoelectric device that can generate electricity from the temperature difference between your fingertips and the environment.

While many kinds of inorganic semiconductors have been studied, organic thermoelectric materials that are flexible and non-toxic have only recently emerged, even though they are easily synthesised, lightweight and cheap.  Such materials have the potential to be used in textiles and even turned into clothing that could use wasted body heat as an energy source.

The researchers, led by Eunkyoung Kim from Yonsei University, optimised a polymerisation and electrochemical redox process to create conducting polymers based on poly(3,4-ethylenedioxythiophene (PEDOT) with good electrical conductivity and relatively high thermoelectric properties, reporting a power factor of more than 1260 μW m^-1 K^-2.

Interested to know more? Read the full article in Chemistry World here…

Read the article from EES:

Flexible PEDOT electrodes with large thermoelectric power factors to generate electricity by the touch of fingertips
Teahoon Park, Chihyun Park, Byeonggwan Kim, Haejin Shin and Eunkyoung Kim
DOI: 10.1039/C3EE23729J