Solar energy is a clean alternative to conventional non-renewable energy sources. However, modern solar panels require the use of toxic materials. A group of scientists from Korea have developed a new sustainable alternative and reported their findings in the journal Nano Energy.
The imminent threat of a climate change crisis is unambiguous and given its urgency, the transition to renewable energy needs to be accelerated. In recent years, solar energy has emerged as one of the most promising candidates for this challenge.
Solar panels are made up of photovoltaic cells, whereby materials that are exposed to light generate electrical current. Modern thin-film solar cells are composed of micrometer or submicron thick layers of photovoltaic material, which allows them to be integrated into flexible and lightweight panels for use in a variety of substrates.
However, this process has some limitations. Professor Jun Ho Kim of Incheon National University, who led the study, explains, “Most thin-film solar cells contain toxic and expensive elements that limit the use of solar cells.” Professor Kim and his team have worked to produce a solar cell using environmentally friendly natural materials that are easy to mine and inexpensive to produce.
Scientists have turned their attention to environmentally friendly kesterite, a natural mineral that acts as a photon absorber. Most solar cells use a cadmium sulfide (CdS) buffer layer to optimize the performance of the kesterite. The contamination associated with the creation of these buffers and the toxicity of cadmium are undesirable for creating green solar cells.
To solve this problem, the researchers studied a promising alternative to CdS – “ZTO buffers”. These are glass substrates coated with zinc and tin oxide. To further improve the efficiency of the solar cell, the team aligned the electron energy levels between the kesterite absorber layer and the ZTO buffer layer. This improved the circulation of electrons between the two layers, increasing cell voltage and overall productivity.
This method is the first to achieve this high performance using extremely environmentally friendly, affordable and inexpensive materials.