Tong Y1, Zhanfeng Li1*, Tian Y1 and Hao Y2
11Key Laboratory of Advanced Transducers and Intelligent Control System, China
2College of Physics and Optoelectronics, China
*Corresponding author: Zhanfeng Li, Key Laboratory of Advanced Transducers and Intelligent Control System, China
Submission: July 20, 2020Published: August 14, 2020
Volume2 Issue2August, 2020
The rapid development of photovoltaics, which directly convert solar energy to electricity, has been achieved by both academia and industry and regarded as one of the most clean and renewable energy resources for the next generations. Although inorganic solar cells presently provide higher efficiencies, the high cost and energy-consuming production process limit their wide application. Therefore, extensive studies have investigated new inexpensive organic photovoltaic systems. Recently, polymers have been studied widely in this promising area owing to their versatile and adjustable physical and chemical properties, among which organic solar cells (OSCs) and perovskite solar cells (PSCs) have attracted considerable attention due to their advantages of low cost, lightweight, and flexibility. Especially in the photocatalysis area, polymers can be used to modify photo-corrosive semiconductors to improve the efficiency and stability of solar hydrogen production. Therefore, based on the important roles that polymers play in high-efficiency solar cells and solar hydrogen generation, we herein provide a mini review on the major applications of polymers in energy conversion and storage fields.
As a promising renewable energy technology, the OSCs have attracted considerable attention due to their excellent features such as lightweight, mechanical flexibility and lowcost methods for fabrication . With the innovative design and efficient application of new polymer materials, which are used as the photo-active layer or buffer layer in OSCs, the power conversion efficiencies (PCEs) of the latest single-junction devices have gradually enhanced to more than 16% . Specifically, the synthesis and employment of poly(3-hexylthiophene) (P3HT) successfully improved the device efficiency from less than 1% in the poly (phenylene vinylene) (PPV) system to 4%-5% [3,4]. Then, the polymers based on the benzodithiophene and thieno [3,4-b] thiophene (PTB7) was further synthesized and applied to OSCs and the corresponding device efficiency was enhanced to 7.4% . Recently, a novel copolymer PM6 was used as a donor material to fabricate the device with a PCE of 16.54% , which will stimulate the design of new polymer materials with high efficiency. A series of D-A1- D-A2 random polymers, such as PTPDBTO-T, PTPDBTO-TT, PTPDBTO-3T, and P2FBT-x, have been synthesized and applied to fabricate the thick active layer device with relatively stable efficiency by our team (Figure 1) [6,7].
In PSCs, the polymers are extensively used to facilitate the nucleation process which can regulate the crystallization of perovskite films and improve the device optoelectronic property and chemical stability . Due to the high carrier mobilities and tunable bandgap of polymers, they can also be employed as hole/electron transporting materials (HTMs/ETMs) and interface layer to enhance the carrier separation efficiency and reduce the recombination by improving the surface of perovskite film. Many researchers including our group have deeply studied the application of polymers as the HTMs in PSCs by designing and synthesizing the novel polymer materials (Figure 1). The conventional HTM, poly(3,4 ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) slowly faded out of interest owing to its low work-function nature which limits the potential open circuit voltage of devices and great acidity which results in relatively poor stability . In order to solve these issues, some neutral and hydrophobic polymer HTMs with deep highest occupied molecular orbital levels, such as poly[N,N′- bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (poly-TPD)  and poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) , have been successfully exploited, and they are playing the leading role in the pursuit of high PCE (yielding PCEs of 15.3% and 19.4% respectively) and high stability. These studies reveal that the application of polymers can provide valuable guidelines for improving the efficiency of PSCs.
Figure 1: Applications of polymers in energy conversion and storage field.
The polymers have been further applied in the field of photocatalysis, promoting the development of visible-light responsive photocatalysts which is indispensable for effective utilization of sunlight . Inorganic semiconductor CdS has become a hotspot for photocatalytic hydrogen production due to its narrow bandgap and appropriate band structure position, but there are problems of rapid recombination of photogenerated carriers and severe photo-corrosion. Some studies have shown that the polymers can be used to modify the inorganic semiconductors with photo corrosive properties to form hetero structured photocatalysts, improving the efficiency and stability of solar hydrogen generation . Inspired by this, we did the following work: the region asymmetric conjugated polymer PR1F  was successfully used to modify the surface of inorganic semiconductor CdS by coordination bond Cd-S, and photocatalytic hydrogen production activity of the organic-inorganic composite CdS/PR1F is nearly 14 times higher than that of CdS without modification (Figure 1). But this discover has not yet been published in a journal. We hope our work could provide a new idea for the improvement of photocatalytic hydrogen production efficiency.
In summary, the polymers can not only be used as new highperformance multi-functional solar materials to influence device’s efficiency and stability in the organic photovoltaic fields, but also be used to modify photocatalysts to improve the efficiency of solar hydrogen production in the photocatalysis area. Consequently, the applications of polymers are significant for improving the energy conversion and storage fields, and the polymers will play a major role in the future.
We acknowledge the National Nature Science Foundation of China (Grant No. 61571317), Key Research and Development (International Cooperation) Program of Shanxi (Grant No. 201603D421042), and Platform and Base Special Project of Shanxi (Grant No. 201605D131038) for financial support.
© 2020 Zhanfeng Li. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and build upon your work non-commercially.