Perovskite solar cells have come a long way in a short time, but there’s still room for improvement. Engineers have now added a layer of quantum dots to the recipe, resulting in a more stable solar cell with near-record efficiency.
Perovskite materials make effective solar cells for a few reasons. Thin films of them are able to efficiently absorb the entire spectrum of visible light, they’re cheap to make, lightweight and flexible.
But of course, there’s a catch. Perovskite solar cells have stability issues and can degrade under real-world conditions, and their efficiency tends to drop on larger scales. In past studies, scientists have tried to improve the stability by adding bulky molecules, old pigments, 2D additives, or chili compounds.
For the new study, researchers at EPFL and the Korea Institute of Energy Research tested out a new ingredient – quantum dots. These tiny particles emit specific colors of light when illuminated, and are beginning to find use in things like TVs and solar cells.
In this case, the team used quantum dots made of a type of tin oxide to serve as the electron-transport layer of the device. This layer shuttles electrons produced by the perovskite into the electrode, so the energy can be used. Compared to the usual titanium dioxide material this layer is made from, the quantum dots improved the device’s capacity for capturing light, as well as reducing an effect that sometimes takes place between the two layers, which normally reduces efficiency.
All up, the team found that perovskite solar cells with a quantum dot layer achieved efficiencies of up to 25.7 percent – just 0.1 percent shy of the current perovskite record set by a device measuring 0.08 cm2 (0.01 in2). Efficiencies for larger solar cells were decent too: the team recorded 23.3 percent efficiency for a 1-cm2 (0.2 in2) cell, 21.7 percent for 20 cm2 (3.1 in2) and 20.6 percent for 64 cm2 (9.9 in2).
The research was published in the journal Science.
Source: EPFL via Eurekalert