Solar Cell Efficiency can be Improved by Slow ‘Hot Electrons’


Photons with higher energy compared to band gap energy of the semiconductor absorbing them give rise to hot electrons. The additional band gap energy is lost quickly because it becomes heat so it doesn’t subscribe to the voltage. Scientists have found a product by which these hot electrons retain their high levels of energy for much longer. This will make it possible to use more of this energy to acquire an increased voltage.

The efficiency of solar panels is hampered with a Goldilocks problem i.e. photons should have the ideal level of energy to become free electrons, which subscribe to the voltage. If photons do not have enough energy, they pass through the solar panel. It results in surplus energy disappears in the form of heat.


It is a result of the creation of high-energy electrons. Before they get extracted from the solar panels, these hot electrons produce excess energy by causing vibrations in the crystalline material of the solar panel. This energy loss puts a control to the most of the efficiency of the solar panels.

Scientists work on a unique kind of solar panel that consists of organic-inorganic hybrid perovskites. Perovskites are named after a mineral with the chemical formula ABX3. In the X position, anions form an octahedron, while in the A position cations form a cube around them, while the main cation takes the B position. Many materials in the perovskite family adopt this crystal structure. Hybrid perovskites contain organic cations in the A position.


Most hybrid-perovskite solar panels contain lead, which can be toxic. Scientists recently published a document describing a record-breaking nine-percent efficiency in a hybrid-perovskite solar panel containing harmless tin in place of lead. The results could only signify the hot electrons stated in the tin-based solar panels that took a lot of time to dissipate their excess energy.

The hot electrons gave off their energy after several nanoseconds in place of some hundred femtoseconds. Their longer lifespan gives them the ability to harvest these electrons energy before it becomes heat. This implies we’re able to harvest electrons with an increased energy and thus develop a higher voltage in the solar cell. Theoretical calculations reveal that by harvesting the hot electrons, the efficiency of most effective hybrid-perovskite solar panels could increase from 33 to 66 percent.

Clean energy (conclusion)

The next phase is to learn why the tin-based hybrid perovskites decrease the decay of hot electrons. Then new perovskites materials might be designed with even slower hot electrons. These tin-based perovskites is actually a game changer, and could ultimately produce a big contribution to providing clean and sustainable energy in the future.