High-efficiency Organic Solar Cells Processed With Green Solvents
Dec 03, 2021
Organic solar cells are developing rapidly, and solar cells produced in laboratories currently have a maximum energy efficiency of over 18%. Energy efficiency measures how much energy in sunlight is converted into useful energy in solar cells. The efficiency limit of organic solar cells is considered to be approximately 24%.
One challenge is to make organic solar cells that are stable enough to operate for ten years or more. Another challenge is that solar cells made in solutions containing toxic solvents and relatively low boiling points can obtain the highest energy. The low boiling point can cause problems in the manufacturing process because the solution evaporates slightly too quickly. The use of higher boiling point, more environmentally friendly solvents will immediately lead to lower energy efficiency. This is a problem that researchers all over the world are trying to solve.
These issues have now been resolved in a joint project led by researchers from Linköping University in Sweden and Suzhou University in China.
They have successfully manufactured solar cells that use high boiling point solutions that do not contain any toxic ingredients and have an energy efficiency of more than 17%. In addition, the green solvent-treated solar module with an area of 36 square centimeters shows a power conversion efficiency of more than 14%. This is the highest efficiency of an organic solar cell module with an active area of more than 20 cm2 so far. These two breakthroughs are of great significance for large-scale commercial breakthroughs in organic solar cell technology.
Zhang Rui, a postdoctoral fellow in collaboration with Professor Gao Feng from the Department of Electronics and Photonic Materials of Linköping University, said: "Our research results can now be used to manufacture organic solar cells for outdoor use on a larger scale."
The functions of organic solar cells are gradually improving. When sunlight in the form of photons is absorbed by the organic semiconductor donor, an "excited state" is formed. Electrons jump to higher energy levels and create holes at lower energy levels, however, they are still attracted. The electrons are not completely released, and no photocurrent is generated. The researchers conducted experiments and they added various acceptor materials that accept electrons, thereby freeing them to generate photocurrent.
A few years ago, Chinese researchers developed a new type of acceptor material called Y6, which can provide high efficiency for organic solar cells.
The work described in the joint publication has now been achieved to find a guest molecule called BTO, which ensures that the Y6 molecules in the solar cell are stacked in such a tight and stable manner in the green solvent, which can generate photocurrent. efficient. Adding BTO can also efficiently manufacture larger area solar cells.
"Our strategy sets clear design rules for optimizing the interaction between the organic donor and acceptor in the multi-component mixture, and meets the key requirements for the future development of organic photovoltaic technology," said Professor Li Yaowen of Soochow University.
