Organic photovoltaics: Polymer solar cells record efficiency of 19.3%

The latest news for organic polymer photovoltaics

(sustainabilityenvironment.com) – New record for polymer solar cells of organic photovoltaics. A group of researchers from Hong Kong Polytechnic University (PolyU) has brought the conversion efficiency of this technology to 19.31 percent thanks to a new production technique. A step forward that, according to the same scientists, will probably create “huge opportunities in applications such as portable electronics and photovoltaic integrated into buildings“.

What are polymer solar cells?

Polymer solar cells, also called plastic solar cells, belong to the organic photovoltaic industry. They have a layer structure consisting of a transparent front electrode, a semiconductor polymer active layer, and a back electrode molded onto a plastic substrate.

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Despite the continuous progress of research, polymer photovoltaics has always kept to the margin of the market due to low efficiencies. The main problem of these cells lies in the high losses due to the recombination of charge carriers. This is why in their realization is usually used a separation surface; more precisely a mixture between a donor material and an acceptor (bulk heterojunction-BHJ, ie Heterojunction to mass dispersion) that avoids recombination between electrons and gaps. Efficiency, and thus the quality of the active layer, is directly related to the molecular distribution and stacking of this donor and acceptor mixture.

The way without additives of PolyU

It is at this level that the work of the PolyU fits. Scientists developed an intermediate state manipulation strategy for advanced organic solar cells using 1,3,5-trichlorobenzene. This compound acts as a crystallization regulator, optimizing the crystallization process of the film and regulating the self-organization donor-acceptor mixture.

Unlike the traditional solvent additive approach, which causes excessive molecular aggregation, the new technique promotes the formation of a more orderly molecular stacking and favorable molecular aggregation. As a result, the loss of recombination is reduced. And the conversion efficiency of polymer solar cells is greatly increased.

“The latest study shows a record low non-radiative recombination loss of 0.168 eV in a binary OSC with a PCE of over 19%”, explains Prof. Li Gang who led the research. “This is a very encouraging result for the long-standing research on OSCs that I have conducted over the past two decades. We have already achieved better OSC efficiency, and this will subsequently help accelerate the applications of solar energy”. The research appeared in Nature Communications.