Nav: Home

Why modified carbon nanotubes can help the reproducibility problem

October 18, 2019

Our search for sustainable energy generation technology has led researchers to investigate various materials and their combinations in many types of devices. One such synthetic material is called "perovskite", which is low-cost and easy to produce, and can be used in solar cells. Perovskite solar cells have attracted much attention because their power conversion efficiency (that is, their efficiency at turning sunlight into electricity) has seen dramatic improvements in recent years. However, it has proven difficult to implement them for large-scale energy generation because of a handful of issues.

One problem that perovskite solar cells face is reproducibility. This means that it is hard to consistently create perovskite crystal layers free of defects and holes, which means that deviations from design values are always likely to occur, which reduce their efficiency. On the bright side, researchers have found that the efficiency of these cells can be boosted by combining perovskite with carbon nanotubes (CNTs). The mechanism by which CNTs and perovskite bond together and how this affects the performance of CNT perovskite solar cells has not been studied in depth. In particular, the ability of pure CNTs to bond to perovskite is not very good, and this could compromise the structural and conducting properties at the interface of both materials.

Hence, a team from Tokyo Tech lead by Prof. Keiko Waki conducted a series of experiments on perovskite solar cells combined with different types of CNTs in an attempt to both improve their performance and stability and understand the underlying mechanisms. They used not just pure CNTs, but also CNTs that bore "oxygen-containing functional groups" in their structure, which have been known to strengthen the interaction between the CNTs and perovskite, resulting in better interfaces and enhancing the crystallization of perovskite.

This research consisted of several experiments that provided insight into many aspects of CNT-perovskite interactions. First, they demonstrated the superior electrical performance of cells with functionalized CNTs over those with pure CNTs and found evidence supporting that larger crystals and fewer surface defects occur when using functionalized CNTs. Then, the team inferred that the perovskite in the cells would undergo a recrystallization process if stored in the dark, and that the presence of the functional groups in CNT would have a significant effect on this process. This was confirmed by storing the cells for over two months and measuring their electrical characteristics afterwards (Fig. 1). "We have discovered the self-recrystallization ability of perovskite at room temperature, whose morphology greatly improved after long-term storage. However, the most interesting result was the ability of functionalized CNTs to make use of the self-recrystallization nature to form a stronger junction between the perovskite and CNTs through the reconstruction" explains Prof. Waki. Most notably, the functionalized CNTs improved the contact between the two materials greatly and the functional groups served as a protection against attacks from moisture on the perovskite, allowing the self-recrystallization and interface reconstruction to proceed without noticeable degradation. The research team also found that the recrystallization process could be immensely sped up by constantly subjecting the solar cells to frequent measurements, but this ultimately affected their stability and degraded them.

Such in-depth studies on perovskite solar cells and ways to enhance them are very valuable because they get us closer to new sources of clean energy. "We hope this study contributes toward the production of perovskites with higher stability and reproducibility," concludes Prof. Waki. These findings will serve as another stepping stone so that we may one see perovskite solar cells as a key technology to preserve our planet.
-end-


Tokyo Institute of Technology

Related Solar Cells Articles:

Next gen solar cells perform better when there's a camera around
A literal ''trick of the light'' can detect imperfections in next-gen solar cells, boosting their efficiency to match that of existing silicon-based versions, researchers have found.
On the trail of organic solar cells' efficiency
Scientists at TU Dresden and Hasselt University in Belgium investigated the physical causes that limit the efficiency of novel solar cells based on organic molecular materials.
Exciting tweaks for organic solar cells
A molecular tweak has improved organic solar cell performance, bringing us closer to cheaper, efficient, and more easily manufactured photovoltaics.
For cheaper solar cells, thinner really is better
Researchers at MIT and at the National Renewable Energy Laboratory (NREL) have outlined a pathway to slashing costs further, this time by slimming down the silicon cells themselves.
Flexible thinking on silicon solar cells
Combining silicon with a highly elastic polymer backing produces solar cells that have record-breaking stretchability and high efficiency.
Perovskite solar cells get an upgrade
Rice University materials scientists find inorganic compounds quench defects in perovskite-based solar cells and expand their tolerance of light, humidity and heat.
Can solar technology kill cancer cells?
Michigan State University scientists have revealed a new way to detect and attack cancer cells using technology traditionally reserved for solar power.
Solar cells with new interfaces
Scientists from NUST MISIS (Russia) and University of Rome Tor Vergata found out that a microscopic quantity of two-dimensional titanium carbide called MXene significantly improves collection of electrical charges in a perovskite solar cell, increasing the final efficiency above 20%.
Welcome indoors, solar cells
Swedish and Chinese scientists have developed organic solar cells optimised to convert ambient indoor light to electricity.
Mapping the energetic landscape of solar cells
A new spectroscopic method now makes it possible to measure and visualize the energetic landscape inside solar cells based on organic materials.
More Solar Cells News and Solar Cells Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Making Amends
What makes a true apology? What does it mean to make amends for past mistakes? This hour, TED speakers explore how repairing the wrongs of the past is the first step toward healing for the future. Guests include historian and preservationist Brent Leggs, law professor Martha Minow, librarian Dawn Wacek, and playwright V (formerly Eve Ensler).
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.