In solar panels, silicon material has an unassailable lead. The reason for the lack of an alternative material has been the low traction of thin-film technologies as raw materials were costly and inefficient.
As an alternative to silicon, research has been expanding on perovskite solar cells considering its abundance and potential for higher efficiencies. This is despite its limitations to suit the conditions of mass manufacturing and the problem of material decay.
In mitigating the decay problem, scientists at the National Renewable Energy Lab (NREL) had been conducting research. In the course of the research, they have developed a perovskite ink that can solve its limitation in mass-manufacturing.
The starting point of the photovoltaic ink was the formation of a simple perovskite from a mixture of iodine, lead, and methylammonium.
Though the material could form photovoltaic crystals easily the problem of slow drying at higher temperatures was a drag as it would make manufacturing slow and will also add cost up costs.
To address the problem, the team deployed a "negative solvent" by substituting chlorine for the iodine.
The experiment was aimed at hastening crystal formation and faster settling. It worked and the perovskite ink dried up in a minute even at 100 degrees Celsius onto a surface.
Drying at such high speeds is a boon in roll-to-roll manufacturing in which spun off sheets are added and rolled back frequently.
Perovskite Offers Flexible Efficiency
The ink also gave positive results in blade coating where more ink is applied with the unused part chipped out while running the coated surface beneath a blade.
In terms of efficiency, ink coated individual cells showed good efficiencies at 17 percent and beyond. Fullerenes coating escalates the efficiency further taking it to 19 percent and above. However, silicon does not offer such a flexibility though it is easier to produce.
Perovskites As Substitutes For Silicon
Perovskites are a class of materials with a general crystal structure. Most of them involve a small organic chemical and metals like lead and other simple chemicals.
Some of the best perovskites have been showing efficiencies more than over 20 percent, almost close to silicon. Perovskites stand out for amazing ease in forming water-based solutions to coat all kinds of materials.
Nano Particles To Double Solar Panel Efficiency
The bulk of the solar panels made of silicon has a limited average efficiency of just 20 percent. The theoretical upper limit of silicon efficiency is 30 percent while scientists have attained only 25 percent in silicon. That means a silicon panel is able to utilize only 25 percent of solar spectrum with the remaining energy going waste.
To generate electricity, a solar cell receives photons from sun rays and ejects electrons to start the electric circuit. The layer where electrons are excited and ejected is called the Electron Selective Layer.
One reason for the restricted efficiency has been that the silicon cells are capturing light waves from the red spectrum of sunlight. Now efforts are underway to use nano-materials that can capture sunlight in the red and blue spectrum with double the efficiency.
Oslo University's researchers attached to the Centre for Materials Science and Nanotechnology (SMN) has been working on a new panel design based on nanotechnology.
According to Bengt Svensson, the project leader, their modified panel has two different energy-capturing layers. First is silicon material that takes energy from the red wavelength of incoming sunlight. There is a second layer made of copper oxide to capture light waves from the blue spectrum of sunlight. Together they absorb around 45 percent energy with reduced energy loss.