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Thursday, 23 Nov 2017

UNIST researchers develop highly stable perovskite solar cells using improved encapsulation

Using fluorine to create a 2D material with high hydrophobicity resulted in 82% stability relative to initial performance over 30 days of air exposure without encapsulation

UNIST - Highly stable perovskite solar cells

25 Oct 2017 | Editor

Researchers at UNIST have recently published research findings on a highly stable perovskite solar cells (PSCs), using edged-selectively fluorine (F) functionalised graphene nano-platelets (EFGnPs). The key step seems to be down to using fluorine, a low-cost alternative to gold.

This study jointly led by Professor Jin Young Kim in the School of Energy and Chemical Engineering at UNIST in collaboration with Dong Suk Kim of Korea Institute of Energy Research (KIER). Assistant Professor Gi-Hwan Kim in the School of Energy and Chemical Engineering at UNIST partook in this study, as the lead author.

UNIST - Research team

Figure: UNIST - Research team

The researchers said over the past few years perovskite solar cells have been widely promoted as the "next-generation" solar cells with the potential to surpass silicon cells' efficiency.

However, perovskite materials are sensitive to moisture and without proper encapsulation will not survive for long - less than 24 hours. So stability and cost issues in PSCs are at the moment considered to be a major barrier to further advancements toward commercialisation.

To solve these issues and make progress toward the commercialisation of PSCs, Professor Kim and his team introduced a highly stable p-i-n structure for PSCs using fluorine functionalised EFGnPs to fully cover the perovskite active layer and protect against the ingress of water for high-stability PSCs.

UNIST - Highly stable p-i-n perovksite structure

Figure: UNIST - Highly stable p-i-n perovksite structure

Edged-selectively fluorine (F) functionalised graphene nanoplatelets with a p–i–n structure of perovskite solar cells achieved 82% stability relative to initial performance over 30 days of air exposure without encapsulation.

These newly-developed perovskite solar cell device were fabricated using solution processes. The researches said next-generation solar cells offer are advantages in that they have a simple manufacturing process and a lower manufacturing cost, compared to existing silicon-based solar cells.

This research has been supported by the National Research Foundation of Korea Grant (NRF) and the Creative Research Initiative (CRI) program. This work has been also supported by the Development Program of the Korea Institute of Energy Research (KIER) and UNIST.

"Fluorocarbons, such as polytetrafluoroethylene (Teflon) are well-known for their superhydrophobic properties and comprise carbon fluorine (C-F) bonding."

"By substituting carbon for fluorine, we have created a two-dimensional material with high hydrophobicity, like Teflon. Then, applied it to PSCs. "

Professor Gwi-Hwan Kim, UNIST

"This study overcame weakness of perovskite solar cells that have high efficiencies but low stability."

"This breakthrough holds substantial promise as the base technology for the application of the next-generation solar cells, as well as various IoT devices and displays."

Professor Jin Young Kim, UNIST

Fluorine Functionalized Graphene Nano Platelets for Highly Stable Inverted Perovskite Solar Cells

Gi-Hwan Kim | Hyungsu Jang | Yung Jin Yoon | Jaeki Jeong | Song Yi Park | Bright Walker | In-Yup Jeon | Yimhyun Jo | Hyun Yoon | Minjin Kim | Jong-Beom Baek | Dong Suk Kim | Jin Young Kim

Nano Lett., 2017, 17 (10) | pp 6385–6390 | DOI: 10.1021/acs.nanolett.7b03225

Abstract

Edged-selectively fluorine (F) functionalized graphene nanoplatelets (EFGnPs-F) with a p–i–n structure of perovskite solar cells achieved 82% stability relative to initial performance over 30 days of air exposure without encapsulation. The enhanced stability stems from F-substitution on EFGnPs; fluorocarbons such as polytetrafluoroethylene are well-known for their superhydrophobic properties and being impervious to chemical degradation. These hydrophobic moieties tightly protect perovskite layers from air degradation. To directly compare the effect of similar hydrophilic graphene layers, edge-selectively hydrogen functionalized graphene nanoplatelet (EFGnPs-H) treated devices were tested under the same conditions. Like the pristine MAPbI3 perovskite devices, EFGnPs-H treated devices were completely degraded after 10 days. The hydrophobic properties of EFGnPs-F were characterized by contact angle measurement. The test results showed great water repellency compared to pristine perovskite films or EFGnPs-H coated films. This resulted in highly air-stable p–i–n perovskite solar cells.

www.unist.ac.kr   


About Ulsan National Institute of Science and Technology

Source: Ulsan National Institute of Science and Technology


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