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Friday, 21 Jul 2017

Researchers develop organic solar cell with improved operation stability and 11.6% PCE

By applying a small amount of macromolecular additive to the photoactive layer the research team developed an effective and simple strategy to improve and stabilise the performance of OPVs

10 Oct 2016 | Editor

A new type of organic solar cells (OSC) with 11.6% efficiency has been developed by a research team, affiliated with UNIST. This solar cell maintained almost 80% of its initial efficiency after 60 days long-term test under elevated temperatures up to 120 degrees.

In the study, the research team, led by Prof. HyeSung Park and Prof. Chang Duck Yang of Energy and Chemical Engineering has developed an effective and simple strategy to simultaneously improve and stabilise the performance of OPVs by applying small amounts of the macromolecular additive to the photoactive layer in OPV. This is a unique and unprecedented method, which applies the macromolecular additive to control the molecular weight.

The team reports that "The use of the macromolecular additive introduced in this study has great potential for broad applications with other OSC systems, which will accelerate the commercial viability of photovoltaic technology."

Organic solar cells are made of thin layers of organic materials with thickness in the 100nm range. The light-absorbing material of OSCs, called the photoactive layers aborbs sunlight to generate electric charge carriers. The efficiency of OSCs are often affected by the materials added to the photoactive layers.

In this work, the research team introduced the first demonstration of the use of a well-known n-type conjugated polymer, as the 'macromolecular additive' into the photoactive layer of OSCs, and report a remarkable enhancement in the device performance yielding unprecedented power conversion efficiency (PCE) of 11.6% with improved stability.

UNIST - OSC on rigid and on flexible substrates

Figure: UNIST - OSC on rigid and on flexible substrates

Using the proposed method, they also demonstrated strong thermal stability in the additive-modified OSCs at elevated temperatures, as well as long-term operation stability. They reported that a stable PCE as high as 80% was still maintained after 60 days long-term operation under a high temperature environment (120?). In addition, by using the ITO-free architecture on flexible PET substrates, the team successfully demonstrated flexible solar cells processed with the macromolecular additive.

UNIST - Current density–voltage characteristics

Figure: UNIST - Current density–voltage characteristics with (a) different molecular weights and (b) varying amounts of the high-quality n-type macromolecular additive

This study also includes the analysis of the optimisation of power conversion efficiency in OSCs, the charge carrier transport properties in OSCs, as well as the changes in the morphology of the photoactive materials induced by the macromolecular additive. The research team attributes the improved performance to advantageous changes in the morphology of the photoactive materials induced by the macromolecular additive.

This work was supported by Mid-career Researcher Program and Individual Basic Science & Engineering Research Program through the Korean Ministry of Science, ICT & Future Planning (MSIP).

Prof. Park said, "Due to its great applicability and easy accessibility, the use of the macromolecular additive introduced in this study has great potential for broad applications with other OSC systems, which will accelerate the commercial viability of photovoltaic technology."
Prof. Yang said, "Our research is important in showing the influence of molecular weight (MW) on power conversion efficiency (PCE) of OSCs."

The use of an n-type macromolecular additive as a simple yet effective tool for improving and stabilizing the performance of organic solar cells

Kwang Hyun Park | Yujin An | Seungon Jung | Hyesung Park | Changduk Yang

Energy Environ. Sci. | 2016, Advance Article | DOI: 10.1039/C6EE02255C

Received 03 Aug 2016 | Accepted 12 Sep 2016 | First published online 12 Sep 2016

Abstract

The discovery of an easy and powerful way to further improve and stabilize the performance of organic solar cells (OSCs) from the current levels would advance their commercialization. In this work, an unprecedented power conversion efficiency (PCE) of 11.6% with improved stability is demonstrated by using a high-quality n-type macromolecular additive P(NDI2OD-T2) via a simple route without additional processing steps, where the high-quality P(NDI2OD-T2) is isolated by a THF-soaking treatment. We attribute the improved performance to advantageous changes in the morphology of the photoactive materials induced by the macromolecular additive. In addition, using the ITO-free architecture on a flexible PET substrate, we obtain an impressive PCE of 5.66% in macromolecular additive-processed devices. Due to its great applicability and easy accessibility, the use of the macromolecular additive introduced in this study has great potential for broad applications with other OSC systems, which will accelerate the commercial viability of photovoltaic technology.

www.unist.ac.kr   


About Ulsan National Institute of Science and Technology

UNIST is a post-secondary institution located in the heart of Korea’s largest industrial city, Ulsan, South Korea. Since its opening in 2009, UNIST has truly become one of the world’s leading science and technology universities. UNIST aims to be ranked within the top 10 science and technology universities by 2030.

Source: Ulsan National Institute of Science and Technology


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