Diffuse light solar cell can generate electricity even on cloudy days

Let us imagine the following scenario: no longer need to charge the phone, kindle or tablet, is it a pleasant surprise? Recently, some researchers said that they have discovered a solar cell that can use low-intensity diffuse light inside buildings and under cloudy skies to generate electricity, and the working efficiency has reached a certain value. This kind of solar battery may liberate charging equipment in the future, and the casing of the equipment can continuously charge the equipment, so that it does not need to be plugged into a socket to charge. Diffuse solar cells are nothing new, and they basically rely on expensive semiconductor materials to achieve the best results. In 1991, Michael Graetzel, a chemist at the Federal Institute of Technology in Lausanne, Switzerland, invented the so-called dye-sensitized solar cells (DSSCs), which can achieve the best performance in dim light and are more effective than standard solar cells. Cheap. Under sunlight, the best DSSCs can only convert 14% of solar energy into electricity, while the conversion efficiency of standard solar cells is 24%. The main reason behind this is that light energy comes too fast, and DSSCs cannot be converted in time. Therefore, when light energy is irradiated at a slow pace, such as low-intensity indoor light, the conversion efficiency of DSSCs can be increased to 28%. DSSCs are a bit different from standard silicon solar cells: In standard silicon solar cells, the absorbed sunlight excites electrons on silicon atoms to higher energy levels, allowing them to skip adjacent atoms and move toward the anode. The electrons are collected by the positive electrode and shunt into the circuit so that the circuit can work. The leaving electrons leave holes in the silicon atoms. The holes can also move. As time accumulates, the holes will flow to the negative electrode where they overlap with the electrons in the external circuit. Now the silicon atom charge in the solar cell is renewed. Balance so that it can continue to generate electricity. And DSSCs have increased the complexity of power generation to another level. There are still electrodes for collecting positive and negative charges at both ends, but in the middle, it is no longer just silicon, but other materials. The typical material is titanium dioxide (TiO2) particles. Titanium dioxide is not a good light-absorbing material. Researchers tried to coat the surface of the particles with a special light-absorbing material—organic dye molecules. The absorbed photons excite the electrons and holes of these dye molecules, and the excited electrons are immediately transferred to the titanium dioxide particles, and then move to the positive electrode via the titanium dioxide particles. At the same time, these holes are transferred to the electrolyte (conductive liquid) and finally reach the negative electrode. The problem with DSSCs is that the holes move slowly in the electrolyte, which causes the holes to tend to accumulate near the dye and titanium dioxide particles. Once the excited electrons encounter the holes, they will encounter each other and generate heat instead of electricity. In order to solve this problem, the researchers tried to use a thinner electrolyte layer to facilitate the holes to reach their destinations at the shortest distance. However, any defect in the thin electrolyte layer may cause the device to short-circuit, and a fatal blow at any time can cause the entire solar cell to collapse. Now, Graetzel and his colleagues have come up with another possible solution. They designed a combination of dye and hole-conducting molecules, and then tightly wrapped around the titanium dioxide particles, thus forming a tight fit without any defects. This solves the problem that the holes with slow moving speed have to travel a long way to reach the negative electrode. They published a report in Joule magazine on the 23rd, claiming that this compact layer increases the conversion efficiency of DSSCs to diffuse light to 32%-close to the highest theoretical value. Michael Wasielewski, a chemist at Northwestern University, said: 'This is really a very good progress.' Although the conversion efficiency of this new dye-sensitized cell to direct sunlight is only 13.1%, he pointed out that due to the conversion efficiency of diffuse light An increase of nearly 20% has given people hope that they can find new ways to improve the conversion efficiency under full sunlight.