Researchers at India’s Tata
Institute of Fundamental Research (TIFR) have developed a compact lithium-ion
battery with photosensitive materials that can be directly recharged with solar
According to the scientists,
previous efforts to channel solar energy to recharge batteries used
photovoltaic cells and batteries as separate entities. Solar energy, thus, was
converted by the photovoltaic cells into electrical energy that was
consequently stored as chemical energy in the batteries. The energy stored in
these batteries was then used to power electronic devices.
But this relay of energy from one
component to the other, that is, from the photovoltaic cell to the battery,
leads to energy losses. To address this issue, the team at TIFR led by Amar
Kumar started to explore the use of photosensitive components inside batteries
At the same time, the group
decided that it was necessary to tackle some of the most common pitfalls of
solar batteries, namely, their reduced ability to harness enough solar energy
as time passes; their use of organic electrolytes, which may corrode the
photosensitive organic component inside a battery, and the formation of side
products that hinder the sustained performance of a battery in the long term.
Kumar and his colleagues began
exploring new photosensitive materials which can also incorporate lithium and
build a solar battery that would be leak-proof and operate efficiently in
In a paper published in the journal Nano-Micro
Small, the team explains that solar batteries which have two electrodes usually
include a photosensitive dye in one of the electrodes physically mixed with a
stabilizing component which helps drive the flow of electrons through the
But an electrode, which is a
physical mixture of two materials, has limitations on optimal usage of the
surface area of the electrode. To avoid this, the researchers created a
heterostructure of photosensitive molybdenum disulphide MoS2 and molybdenum
oxide MoOx to function as a single electrode.
Being a heterostructure wherein
the MoS2 and MoOx have been fused together by a chemical vapour deposition
technique, this electrode allows for more surface area to absorb solar energy.
Thus, when light rays hit the electrode, the photosensitive MoS2 generates
electrons and simultaneously creates vacancies called holes. MoOx keeps the
electrons and holes apart and transfers the electrons to the battery circuit.
The scientists found that this
solar battery, which was assembled from scratch, operates well when exposed to
simulated solar light.
Following these findings, Kumar
and his co-authors started working towards unearthing the mechanism by which
MoS2 and MoOx work in tandem with lithium anodes resulting in the generation of
“While this solar battery
achieves a higher interaction of photosensitive material with light, it is yet
to achieve the generation of optimum levels of current to fully recharge a
lithium-ion battery,” they said in a media statement.