The performance pf perovskite-based solar cells is affected by several factors, one of which can be ion defects that can move around. As these defects move, they affect the internal electric environment within the cell. The Perovskite material is responsible for absorbing light to create electronic charge, and also for helping to extract the charge into an external circuit before it is lost to a process called 'recombination'. Most of the detrimental recombination can occur in different locations within the solar cell. In some designs it occurs mainly within the perovskite, while in others it happens at the edges of the perovskite where it contacts the adjacent materials known as transport layers.

Now, researchers from the Universities of Portsmouth, Southampton and Bath have developed a way to adjust the properties of the transport layers to encourage the ionic defects within the perovskite to move in such a way that they suppress recombination and lead to more efficient charge extraction - increasing the proportion of the light energy falling on the surface of the cell that can ultimately be used.

Researchers from the Chinese Academy of Sciences have reported that the introduction of a certain amount of graphdiyne (25%), a form of carbon material invented by Chinese scientists with independent intellectual property rights, as a host material in perovskite solar cells can successfully push the device efficiency up to 21.01%, achieving multiple positive effects of highly crystalline qualities, large domain sizes and few grain boundaries.

The researchers also revealed that the current-voltage hysteresis was negligible, and device stability was improved as well. It was found that graphdiyne as the host active material significantly affects the crystallization, film morphology and a series of optoelectronic properties of perovskite active layer.

What are Quantum Dots?

Quantum dots (QDs) are semiconducting nanocrystals that are very small ' only a few nanometres in size. In display technologies, the most common types of QDs used are composed of a metal chalcogenide core. These QDs have the chemical formula XY ' where X is a metal and Y is sulfur, tellurium or selenium (e.g. CdTe, CdSe, ZnS) ' which is encased with the shell of a second semiconductor (e.g. CdSe/CdS). Their tiny dimensions mean that charge carriers are confined in close proximity, which gives QDs optical and electronic properties that are substantially different from those of large semiconductor crystals.

QLEDs vs OLEDs

In particular, QDs have enhanced light absorption and emission, making them particularly suitable for display technologies. Metal chalcogenide quantum dots (MCQDs) have already made it into commercial products ' most notably, in Samsung's QLED television range. Here, a blue LED backlight excites a layer of quantum dots on an LCD panel, causing them to emit light. The color of light emitted by the quantum dots depends on their size ' with small dots emitting blue light, and progressively larger dots emitting green, yellow, orange, and red light.

Left: Core-shell quantum dot structure. Right: The size of the dot defines the color of light that the dot emits. (Source: Ossila.com)

Swift Solar, A U.S startup designing and manufacturing perovskite solar panels, has announced raising $4.6 million as part of a $6.6 million investment round.

The team at Swift Solar in Colorado includes leading solar technologists from Stanford, MIT, Cambridge (UK), Oxford (UK), and the University of Washington, with expertise in perovskite photovoltaic technology and scale-up. Swift's core technologies range from new solar cell architectures to specialized manufacturing techniques initially developed in the labs at Stanford and MIT.