Education

Tailor made solar panels

 By Luca Longo

Conventional solar modules based on silicon will soon be joined by new organic solar panels that are cheaper and offer a wealth of extra benefits…

The solar panels that we know quite well, allow us to generate clean, efficient energy, but they have some flaws. There’s the price, to begin with. It costs a lot to produce crystalline silicon that’s pure enough, cut it into wafers, dope it, fix the electrode grid and back counter electrode, fit each cell and wire it up to the other cells in the module, mount it, protect it with a pane of glass and install the whole system in its wired panel frame. Later, at the end of its life, we should think about the costs of separating and recycling each item.
But scientific and industrial research are heading in completely different directions. Among these, one of the most promising is OPV, which stands for Organic PhotoVoltaics. Specialist research centres all over the world are experimenting with combinations of organic molecules and polymers able to capture sunlight and use it to activate special molecules, sensible to the light, force them to expel electrons and finally generate an electric current. All without using any silicon atom.

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OPV cells can be printed on light, flexible media, like rolls of clear plastic film or even paper. The end result is extremely light, flexible solar panels in any shape you want

In Italy too – at Eni Renewable Energy and Environmental Research Centre – innovative solar modules based on OPV have been designed and tested, also in collaboration with the Technical Research Center of Finland, MIT in Boston, the Italian National Research Council (CNR) and numerous Italian universities. The good news for the environment are that these new solar cells based on organic substances are so thin that, disregarding the thickness of the supporting tool, you’d need to pile thousands of them on top of one another to match the thickness of a sheet of paper. For the sake of comparison, you can produce just over a couple of square metres of solar module using a kilogram of crystalline silicon (not counting the weight of all the rest of the panel). With a single kilo of the organic inks that make up an OPV cell, on the other hand, you could cover an entire football pitch (10.000 square meters) with solar panels.
Focusing on OPV technology, Eni can produce solar cells in a completely different way compared to conventional modules. The cells are printed using systems practically identical to the ones used for the realization of glossy magazines. Instead of progressively printing layers of ink in different colours, first you print the cathode, then a conductive layer of electrons, then the photoactive layer, then a layer carrying positive charges and then you cover everything with the anode. It can be printed on light, flexible media, like rolls of clear plastic film or even paper. The final results are extremely light, flexible solar panels in any shape you want.

Eni researchers at the Renewable Energy and Environmental Research Centre explain OPV cell technology in this short video

OPV modules can actually be tailor made. Depending on the printing  design, you can match the electrical characteristics (voltage and amps) to the requirements of the intended application and realize the shape that you want, so architets and engineers can eliminate constraints on their design specs. These modules still show a lower maximum efficiency in ideal conditions than expensive silicon panels, but whereas silicon panels need to be positioned exactly, facing south at a precise angle, organic panels can generate energy even with diffused light. Silicon panels don’t operate at dawn, at dusk, in fog or when it’s cloudy. OPV panels, on the other hand, keep generating energy however they’re positioned in relation to the Sun.
They don’t work at night of course, but they do start again as soon as dawn breaks, even when the Sun is hidden by clouds! OPV cell research may soon successfully be built into many electrical or electronic portable devices or items that can’t be connected to an electrical network. These range from sensors (for home automation, security and environmental monitoring) to phones, tablets and other portable devices and could be inserted on bags, curtains, sails and other surfaces where installing a silicon panel wouldn’t make any sense. The fact that organic solar modules are light and easy to transport means that they may soon be used in remote areas that lack infrastructures needed for the transport of heavy silicon panels, enabling us to bring electricity to people and whole communities that still don’t have access to this major factor in economic and social development.

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OPV cell devices may soon successfully be integrated into many electrical or electronic portable devices or ones that can’t be connected to an electrical network

However, the next step will be to apply OPV to Building Integrated PhotoVoltaics (the experts call it BIPV for short). The idea is to use these new solar cells directly inside the structural elements of buildings rather than on top of them: bricks, roof tiles, interior tiles, but also noise barriers and all surfaces exposed to light in every direction. In any case, we’ll be talking about it here soon!

READ MORE: Solar’s window of opportunity by RP Siegel

about the author
Luca Longo