A research team led by Prof. LI Gang, Associate Director of Research Institute for Smart Energy (RISE), Chair Professor of Energy Conversion Technology of the Department of Electrical and Electronic Engineering, Sir Sze-yuen Chung Professor in Renewable Energy, has successfully developed a new generation of perovskite–organic tandem solar cells (POTSCs) that not only deliver high power-generation efficiency but also effectively resist the damage caused by negative voltage. Even under an extreme reverse-bias of –40 V, the tandem devices retain more than 90% of their initial power-generation efficiency, far surpassing all existing thin-film solar technologies, marking a key step towards the practical application of thin-film solar technology.
Thin-film solar technologies, such as cadmium telluride (CdTe), copper indium gallium selenide (CIGS), perovskite and organic solar cells, offer the distinct advantages of their light weight, flexibility and cost-effective manufacturing. However, these materials share a common weakness: owing to their electron–ion hybrid conducting properties, once a solar cell is partially shaded and generates negative voltage, its sustained performance becomes difficult and components may even be damaged. The ability to resist reverse bias is therefore key to determining whether thin-film solar technology is durable and capable of stable, long-term operation.
Organic solar cells (OSCs) have made significant strides in both efficiency and durability in recent years. Yet their behaviour under reverse-bias condition and underlying charge transport mechanisms in bulk heterojunctions remains largely unexplored by the scientific community. Filling the related knowledge gaps is an indispensable step towards the practical application of thin-film solar technology.
The team achieved a breakthrough through its innovative approaches and strategic interventions. By suppressing isolated acceptor clusters within the donor-acceptor intermix region, the team successfully minimised the above-mentioned defects and developed high-performance OSCs with an irreversible breakdown voltage exceeding -35 V. In other words, as long as the negative voltage does not exceed -35 V, the cell will not be permanently damaged. This substantially enhances damage resistance and establishes a new benchmark for the efficiency and stability of OSCs.
The study shows that, by suppressing reverse tunnelling in n-i-p inorganic perovskite-organic tandem solar cells, the organic solar cells successfully protect the perovskite layer. Even after exposure to an extreme reverse-bias of -40 V, the tandem devices retained more than 90% of their initial efficiency. Moreover, these tandem solar cells proved highly stable: after continuous operation at -20 V for 12 hours, they retained 90% of their initial efficiency; and after continuous operation at -4.5 V for 2,000 hours, they retained as much as 97% of their initial efficiency - far surpassing all existing thin-film solar technologies.
The research has been published in the paper “Perovskite–organic tandem solar cells with superior reverse-bias stability,” in Nature Materials.
Press Release: https://www.polyu.edu.hk/en/media/media-releases/2026/0720_polyu-develops-durable-shade-stable-perovskite-organic-tandem-solar-cells/
Full paper: https://www.nature.com/articles/s41563-026-02541-6
Online coverage:
Ta Kung Pao - https://polyu.me/4yvAxmD
Wen Wei Po - https://polyu.me/4fsSedV; https://polyu.me/4w99vQd
Newsbreak - https://polyu.me/4byOBli
Mirage News - https://polyu.me/3TLYCp6
| Research Units | Otto Poon Charitable Foundation Research Institute for Smart Energy |
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