Brighter Future for Solar Lights as Solar Cell Efficiency gets Higher
between electrodes and perovskite raising the performance up to 20.7%, which was around 18% earlier.
Scientists in the United States came up with a new technique of applying low-cost organic pigment coating to perovskite solar cells and increased cell's stability efficiency and by 1.2 % reaching 21.1%. The low-cost organic pigment known as quinacridone (QA), widely used as organic pigment for red paints and cosmetics, is used as a surface passivation agent to improve efficiency and stability. It is air-stable, non-toxic and a lot cheaper. What makes it more suitable is its supermolecular structure that gives it physicochemical properties, including high stability against light and heat and a great charge carrier mobility.
QA is applied to halide methylammonium lead iodine (MAPbI3) thin films by a spin-coating-annealing process. If the solar cell had an efficiency of 18.9% without the layer of pigment, it achieved 21.1% with the layer. Even after the usage of 1000 hours, it still has 90% of its initial efficiency. The solar cell becomes hydrophobic by adding the layer of insoluble pigment via facile solution processing and thermal annealing and initiates high stability for thin films and the solar cell. The surface passivation of halide perovskite thin films by low-solubility organic pigment is an answer to the stable perovskite solar cells.
While Americans were at that, a few scientists in Switzerland were able to come up with a 26.5% efficient perovskite-silicon tandem cell with potential for low-cost electricity generation and large-scale production. The device has a single side textured silicon heterojunction (HJT) cell created at a lab with a mixed halide perovskite deposited on top. Though developed in Swiss Center for Electronics and Microtechnology (CSEM), the cell features a screen-printed contacts, while other leading tandem cells rely on thermally evaporated silver contacts, highly expensive in mass production. According to CSEM, though the temperature has to be lowered to 130 degree Celsius to avoid damage to the perovskite, its screen printing process is equal to the silicon heterojunction (HJT) cell produced industrially.
The key to the efficiency is that the organic passivation layer inserted between the two cells boosted the device open-circuit voltage to 1.86 V. Improvements to contact resistance between the fingers and the front electrode also helped it to raise to 76%. Research is going on if using new transparent electrode materials would enhance the performance better than standard indium-tin-oxide, working on light management within the cell, and placing an additional oxide-based microcrystalline contact between the two cell layers.
The news on solar cell efficiency gets better day by day, latest being the world record hitting 30 % efficiency. When perovskite emerged while silicon was the only word for efficiency, it surprised everyone by breaking the efficiency records while paired with silicon. If functioned individually, it could come up to only 20%. The scientists at Helmholtz-Zentrum Berlin (HZB) have achieved an impressive 29.15 percent efficiency with their tandem silicon-perovskite solar cell. Silicon and perovskite work together very well as silicon is good at absorbing infrared light while perovskite is good at absorbing green and blue light. This new device has a perovskite composition with a 1.68-eV band gap. A new substrate made of carbazole-based molecules with methyl group substitution helped electrons flow through to the electrode more efficiently.
As the researchers compete to bring up the most efficient solar cell, all we need to do is resolve to embrace renewable energy in the future to save ourselves by saving the planet that we live on.
- PRIYANKA IYER