Solar cells are the building blocks of photovoltaic solar panels. They are made from light-absorbing materials that convert sunlight into electricity. Normally the light-absorbing material is silicon, which has an energy-intensive manufacturing process.

In the new study, scientists looked at solar cells made from materials known as perovskites. These can be produced cheaply from chemicals mixed into printable or sprayable ink, which then crystallises to form light-absorbing films.
 

However, perovskite films contain charged defects that are likely to impair their performance. Slow movement of these defects is thought to be responsible for a process known as hysteresis, which leads to irregularities in the efficiency with which light is converted to electrical current.

Light-generated electricity exits the solar cell in the form of electrons to be harnessed. This is done via 'contacts' that sandwich the light-absorbing film. Previously, scientists have managed to remove hysteresis by using more 'selective' contact materials that ensure a one-way flow of electrons out of the solar cell.

In theory, changing these contact materials shouldn't have any effect on the movement of the charged defects within the perovskite, so it has remained a mystery why this appeared to 'fix' the hysteresis problem.