PV power marked a breakthrough recently, as Ulsan National Institute of Science and Technology (UNIST) of South Korea announced success in boosting conversion rate of organic PV cells to 12.01% and developing the technology for low-cost mass production of organic PV cells, overcoming the barrier caused by thinness of photoactive layer.

The breakthrough solves a dilemma in the development of organic PV cell, as a thick photoactive layer hampers conversion rate but a thin photoactive layer defies low-cost mass production. Changduk Yang, professor at UNIST, noted that with photoactive layer 100 nm thin now, organic PV cells defy mass production. The breakthrough, therefore, significantly brightens the outlook of organic PV cell, which has been favored by scientists worldwide, since it is pliable and can be coated.

The breakthrough has been achieved via the employment of non-fullerene acceptors (NFAs or IDIC) as the material of photoactive layer, which can boost the PV conversion rate to 12.01%, even if the layer's thickness is increased to 300 nm.

Photoactive layer is the lifeline of PV cells, in charge of converting sunshine into power. In order to produce electric current, PV cell would yield electron hole when absorbing photons and divide electrons with positive electricity and electron-hole particles with negative electricity via charge separation, allowing the particles to reach electrode for power generation. Electrons and electron-hole particles are transmitted via different routes, I and II.

Sang Myeon Lee, a member of the research team, pointed out that the new organic PV cell can transmit electrons via route I and route II simultaneously, different from one route for traditional fullerene-acceptor PV cell, greatly increasing PV conversion rate.

The high conversion rate is credited to NFAs, which boast better light absorption effect and more diversity in energy levels, than traditional fullerene acceptor, plus capability to cut energy loss from charge separation by near 50%.

Yang pointed out that the research has successfully attained optimal charge separation and charge transmission, while solving the bottleneck caused by the thickness of photoactive layers, paving the way for production and commercialization of high-performance organic PV cells.

Commercialization of the new organic PV cell will mark a milestone in PV power application, as, in addition to low-cost materials and applicability of simple printing technology in manufacturing, it can come in a transparent, soft, and pliable form, for applications in architecture, auto production, and even manufacturing of clothes and other textiles.

Result of the research has been published in "Energy & Environmental Science."

Reference:
Introducing High-performance Non-fullerene Organic Solar Cells

(First photo courtesy of UNIST, written by Daisy Chuang)