Solar cells printed on paper

MIT researchers in the United States demonstrated a new type of printing technology that can print solar cells onto thin, soft materials such as regular toilet paper. Although the use of toilet paper as a substrate is not as efficient as actual solar equipment, it is a low-cost printing technology that is widely used for the diversification of various materials.

The new technology is called oxidative chemical vapor deposition (oCVD). The raw material monomer and oxidant are vaporized and then sprayed on the substrate material. The monomer and oxidant meet and polymerize to form a PEDOT film. The PEDOT film can conduct electricity. By controlling the temperature of the substrate, a small nano-pore can be formed, and the silver particles with higher conductivity can be tightly fixed, and the conductivity of the PEDOT film can be enhanced by 1000 times.

MIT chemical engineering professor Karen Gleason and graduate student Miles Bar and others demonstrated the solar cell printing technology on various soft and fragile materials. For example, glutinous rice paper used for spring rolls in restaurants is usually melted when wet, while the new technology is a solvent-free drying method. After printing, glutinous rice paper can be kept intact. They also demonstrated new printing techniques on plastic yam packages that are non-absorbent and that it is difficult for the general process to print on them. Printed solar cells can resist large bending and stretching. In the experiment, the researchers bent a printed plastic substrate material to a radius of less than 5 mm and found that the efficiency was still 99% when it was not bent. The electrodes can also be flexed and stretched to maintain conductivity. To further demonstrate the robustness of the technology, Miles Bar folded a printed solar cell paper into a paper airplane. Even then, paper airplanes can generate electricity.