7. AFFORDABLE AND CLEAN ENERGY

Graded bulk-heterojunction enables 17% binary organic solar cells via nonhalogenated open air coating – Nature Communications

Graded bulk-heterojunction enables 17% binary organic solar cells via nonhalogenated open air coating – Nature Communications
Written by ZJbTFBGJ2T

Graded bulk-heterojunction enables 17% binary organic solar cells via nonhalogenated open air coating  Nature.com

Graded bulk-heterojunction enables 17% binary organic solar cells via nonhalogenated open air coating – Nature Communications

Abstract

Graded bulk-heterojunction (G-BHJ) with well-defined vertical phase separation has the potential to surpass classical BHJ in organic solar cells (OSCs). This work demonstrates an effective G-BHJ strategy using nonhalogenated solvent sequential deposition with nonfullerene acceptor (NFA) OSCs. Spin-coated G-BHJ OSCs deliver a remarkable 17.48% power conversion efficiency (PCE). Techniques such as depth-profiling X-ray photoelectron spectroscopy (DP-XPS) and angle-dependent grazing incidence X-ray diffraction (GI-XRD) are used to visualize polymer/NFA composition and crystallinity gradient distributions, benefiting charge transport. The nonhalogenated solvent enabled G-BHJ OSC via open-air blade coating achieved a record 16.77% PCE. The blade-coated G-BHJ has different D-A crystallization kinetics, suppressing excessive aggregation induced unfavorable phase separation in BHJ. G-BHJ is a feasible and promising strategy towards highly efficient, eco-friendly, and manufacture-friendly OSCs.

Introduction

Bulk heterojunction (BHJ) organic solar cells (OSCs) have gained attention for their unique advantages in creating flexible and roll-to-roll solar cells through solution-processed coating techniques. The power conversion efficiencies (PCEs) have improved significantly due to the development of nonfullerene acceptors (NFAs). However, BHJ strategy has intrinsic limitations for further improvement and technology deployment, including complicated morphology evolution during donor (D) and acceptor (A) mixture, strong dependence on phase separation, limited selection of processing solvents, and challenges in maintaining fill factors (FFs) in thick BHJ active layers. The concept of graded junction has been proposed to address these issues.

Solvent Selection Rules and G-BHJ Formation

The solvent properties of the upper layer are crucial for the morphology of the whole blend. Solvents with poor solubility but fast evaporation, like THF, struggle to achieve high-quality SD-films. Similarly, solvents with excellent solubility and slow evaporation rate, like CB, cannot enable high-quality SD-film either. The balance of solubility and boiling point of the upper solvent is key for forming G-BHJ.

Device Performance

The photovoltaic performances of both traditional BHJ and G-BHJ OSCs were evaluated. The optimal G-BHJ device processed by XY solution exhibited a higher PCE compared to the BHJ device. The improvement in photovoltaic performances in G-BHJ devices mainly originates from the enhanced JSC and FF.

Carrier Dynamics Analysis

The improved JSC and FF are the main factors contributing to the enhanced PCEs of G-BHJ OSCs. The exciton dissociation efficiency (ηdiss) and charge collection efficiency (ηcoll) were investigated to understand the charge separation and collection mechanism.

Molecular Packing and Crystallinity Analysis

The GI-XRD measurements provided details of the molecular packing and crystallinity in the BHJ and G-BHJ active layers. The results showed that utilizing non-orthogonal solvent driven G-BHJ approach facilitates the crystallization structure of PM6.

Thick-Film G-BHJ OSCs

G-BHJ OSCs possess higher tolerance to a wide range of thickness up to 500 nm compared to BHJ OSCs, mainly resulting from superior FFs.

G-BHJ OSCs Fabrication by Blade Coating

The nonhalogenated solvent (XY) enabled G-BHJ OSC via blade coating to achieve an excellent 16.77% PCE in open-air condition, assisted by favorable novel D–A crystallization kinetics comparing to classical BHJ.

Discussion

This work shows that G-BHJ is a feasible and promising strategy towards highly efficient, eco-friendly, and manufacture-friendly OSCs. Smart selection of “green” solvents and engineering deposition conditions or designing new OSC D–A molecules fitting “good” solvents are valuable for future G-BHJ OSC research.

  1. Author Information: The authors include Ying Zhang, Kuan Liu, Jiaming Huang, Patrick W. K. Fong, Gang Li from The Hong Kong Polytechnic University, Xinxin Xia and Xinhui Lu from The Chinese University of Hong Kong, Jiupeng Cao, Guangming Zhao, Ye Zhu, Feng Yan from The Hong Kong Polytechnic University, and Yang Yang from UCLA.
  2. Competing Interests: The authors declare no competing interests.
  3. Data Availability: The experimental data supporting the findings are available within the article and its supplementary information files. Source data are provided with this paper.

Which SDGs are addressed or connected to the issues highlighted in the article?

The article addresses the following Sustainable Development Goals (SDGs):

  • SDG 7: Affordable and Clean Energy
  • SDG 9: Industry, Innovation, and Infrastructure
  • SDG 12: Responsible Consumption and Production
  • SDG 13: Climate Action

What specific targets under those SDGs can be identified based on the article’s content?

Specific targets under the identified SDGs based on the article’s content include:

  • Target 7.2: Increase substantially the share of renewable energy in the global energy mix.
  • Target 9.4: Upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes.
  • Target 12.2: Achieve the sustainable management and efficient use of natural resources.
  • Target 13.2: Integrate climate change measures into national policies, strategies, and planning.

Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

The indicators mentioned or implied in the article that can be used to measure progress towards the identified targets include:

  • Indicator for Target 7.2: The power conversion efficiency (PCE) of organic solar cells (OSCs) as a measure of renewable energy technology performance.
  • Indicator for Target 9.4: The development and deployment of nonhalogenated solvent sequential deposition as an innovation in manufacturing eco-friendly OSCs.
  • Indicator for Target 12.2: The use of nonhalogenated solvents in OSC production as an indicator of responsible consumption and production practices.
  • Indicator for Target 13.2: The reduction of toxic solvent usage and the promotion of green solvents in OSC production as a measure of integrating environmental considerations into industrial processes.

Create a table with three columns titled ‘SDGs, Targets and Indicators” to present the findings from analyzing the article. In this table, list the Sustainable Development Goals (SDGs), their corresponding targets, and the specific indicators identified in the article.

SDGs Targets Indicators
SDG 7: Affordable and Clean Energy Target 7.2: Increase substantially the share of renewable energy in the global energy mix. The power conversion efficiency (PCE) of organic solar cells (OSCs).
SDG 9: Industry, Innovation, and Infrastructure Target 9.4: Upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes. The development and deployment of nonhalogenated solvent sequential deposition as an innovation in manufacturing eco-friendly OSCs.
SDG 12: Responsible Consumption and Production Target 12.2: Achieve the sustainable management and efficient use of natural resources. The use of nonhalogenated solvents in OSC production as an indicator of responsible consumption and production practices.
SDG 13: Climate Action Target 13.2: Integrate climate change measures into national policies, strategies, and planning. The reduction of toxic solvent usage and the promotion of green solvents in OSC production as a measure of integrating environmental considerations into industrial processes.

Copyright: Dive into this article, curated with care by SDG Investors Inc. Our advanced AI technology searches through vast amounts of data to spotlight how we are all moving forward with the Sustainable Development Goals. While we own the rights to this content, we invite you to share it to help spread knowledge and spark action on the SDGs.

Fuente: nature.com

 

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