A collaborative team from Ulsan National Institute of Science and Technology (UNIST), Ulsan University, and Gunsan National University has engineered a multifunctional hole-selective layer (mHSL) designed to dramatically enhance the performance of perovskite/organic tandem solar cells (POTSCs). Reported in Advanced Energy Materials (2025), the thin-film material simultaneously improves both efficiency and durability of tandem solar cells, marking a significant advancement in renewable energy technology.
Tandem solar cells stack two distinct photovoltaic layers to capture a broader spectrum of sunlight, thereby boosting overall energy conversion efficiency. The combination of perovskite and organic materials holds particular promise for producing thin, flexible solar panels suitable for wearable devices and building-integrated photovoltaics (BIPV), positioning them as a next-generation energy solution. By blending two self-assembling molecules, the research team developed a hole-transport layer (HTL) that achieved a record-breaking open-circuit voltage (Voc) of 2.216 V and a power conversion efficiency (PCE) of 24.73%.
This efficiency ranks among the highest ever reported for global perovskite-organic tandem solar cells. Moreover, the device retained over 80% of its initial efficiency after 500 hours of continuous exposure to 65°C heat and light, demonstrating exceptional long-term stability—a critical challenge for commercial viability.
The newly developed HTL is meticulously engineered to align its energy levels with the perovskite active layer, selectively extracting holes while blocking electrons to minimize charge recombination losses. Efficient charge extraction is essential because, after light absorption, electrons and holes must reach their respective electrodes to generate current. Mismatched energy levels can lead to charge losses and reduced efficiency.
Additionally, strong chemical bonds formed between the substituents of the self-assembling molecules (36ICzC4PA and 36MeOCzC4PA) and metal ions within the perovskite layer reduce interfacial defects that impede charge transport and stabilize the crystal structure. The self-assembling nature of these molecules ensures uniform, ultra-thin coatings over large areas, simplifying manufacturing processes and facilitating scalable commercial production.
This breakthrough addresses key hurdles in POTSC technology—efficiency, stability, and scalability—paving the way for broader adoption in flexible electronics, BIPV, and off-grid energy systems. The research underscores the potential of perovskite-organic hybrids to revolutionize renewable energy by offering lightweight, high-efficiency alternatives to traditional silicon-
