PolyU researchers achieve breakthrough efficiency in organic solar cells

Researchers at The Hong Kong Polytechnic University (PolyU) have made a significant breakthrough in the field of organic solar cells (OSCs), achieving a remarkable power-conversion efficiency (PCE) of 19.31%. This breakthrough is expected to enhance the practical applications of these advanced solar energy devices.

The PCE is a crucial measure of the power generated by solar panels, also known as photovoltaics (PVs). The PolyU researchers have set a new record for binary OSCs, which utilize a donor and an acceptor in the photo-active layer.

Led by Prof. Li Gang, a renowned expert in renewable energy and energy conversion technology, the research team developed a novel technique for regulating the morphology of OSCs using 1,3,5-trichlorobenzene as a crystallization regulator. This innovative approach has led to improved efficiency and stability of OSCs.

The team employed a strategy called non-monotonic intermediated state manipulation (ISM) to manipulate the morphology of bulk-heterojunction (BHJ) OSCs, optimizing the crystallization dynamics and minimizing energy loss in non-fullerene OSCs. Unlike traditional methods that rely on solvent additives and excessive molecular aggregation, the ISM strategy promotes the formation of ordered molecular stacking and favorable molecular aggregation. Consequently, the PCE was significantly increased, while the undesired non-radiative recombination loss was reduced. Non-radiative recombination typically hampers light generation efficiency and increases heat loss.

The research findings were published in the prestigious journal Nature Communications, emphasizing the importance of converting solar energy into electricity for achieving a sustainable environment. Although OSCs are cost-effective devices for harnessing solar energy, their efficiency needs to be improved for widespread practical applications.

Prof. Li explained that the existing morphology control methods based on additives faced challenges due to non-radiative recombination loss, which led to decreased open-circuit voltage caused by excessive aggregation. Over a span of two years, the research team developed the non-monotonic ISM strategy to enhance OSC efficiency and reduce non-radiative recombination loss. The publication of their study is expected to invigorate OSC research.

Prof. Li further highlighted the significance of the research, stating that it would make OSC research an exciting field and create numerous opportunities in areas such as portable electronics and building-integrated PVs. The goal is to achieve a PCE of over 20% in low-cost single-junction OSCs, along with improved stability and other unique advantages like flexibility, transparency, stretchability, low weight, and tunable color.

Prof. Li, a highly cited researcher for nine consecutive years, expressed his satisfaction with the study’s outcomes. He emphasized that the record-low non-radiative recombination loss of 0.168 eV in a binary OSC with a PCE exceeding 19% is an encouraging result after his two decades of research on OSCs. The improved efficiency achieved will accelerate the practical applications of solar energy.

In conclusion, the research conducted by the PolyU team has yielded a significant breakthrough in the efficiency of OSCs, with a PCE of 19.31%. This achievement is expected to have far-reaching implications for the field and drive the widespread adoption of solar energy in various applications.

Source: Hong Kong Polytechnic University

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