As the demand for efficient and affordable renewable energy continues to grow, perovskite solar cells (PSCs) have emerged as promising candidates for next-generation photovoltaics. Yet, improving power conversion efficiency while maintaining long-term stability and enabling large-area manufacturing remains a major challenge. Researchers from Xidian University have reviewed recent advances in self-assembled monolayers (SAMs) as hole-selective contacts in inverted perovskite solar cells, highlighting how molecular engineering can optimize buried interfaces, improve charge extraction, and support the development of high-efficiency single-junction devices, tandem solar cells, and scalable photovoltaic modules.
Why These Molecular Layers Matter
In inverted perovskite solar cells, the hole transport layer directly influences perovskite film formation, interfacial defect density, and charge-carrier collection. Conventional materials can introduce limitations, including substrate corrosion, poor surface wettability, insufficient conductivity, and interfacial recombination. SAMs offer an alternative through their molecular-scale thickness, high optical transparency, tunable energy levels, and ability to chemically interact with both the underlying electrode and the perovskite absorber. By minimizing interfacial energy losses without introducing substantial parasitic light absorption, these molecular layers provide an important route toward improving device efficiency and reproducibility.
Innovative Design and Mechanism
The review systematically examines how the three principal components of SAM molecules—the anchoring group, molecular linker, and terminal functional group—govern interfacial behavior. Anchoring groups such as phosphonic acids, carboxylic acids, and silanes determine how strongly molecules attach to transparent conductive oxide substrates. Linker length, flexibility, and conjugation influence molecular packing, interfacial stress, and hole transport, while terminal groups regulate energy-level alignment and interact with defects in the perovskite layer. Together, these molecular features can improve substrate coverage, guide perovskite crystallization, passivate undercoordinated lead-related defects, and suppress non-radiative recombination. The authors also compare preparation methods, including spin-coating, dip-coating, blade-coating, spray-coating, and vacuum deposition, emphasizing that molecular design and deposition conditions must be optimized together.
Outstanding Performance
Reported advances demonstrate the potential of SAM engineering across multiple photovoltaic architectures. Representative single-junction devices have achieved power conversion efficiencies above 26%, including a reported 26.71% for a device using a modified SAM interface. In tandem photovoltaics, SAM-based interfacial strategies have enabled a reported 33.86% efficiency for a perovskite–silicon tandem device with an active area of 1 cm². Progress has also extended to scalable processing: polymeric SAM derivatives have enabled blade-coated perovskite mini-modules with an aperture-area efficiency of 22.2%. These examples illustrate how tailored molecular structures can simultaneously support efficient charge extraction, improved interfacial quality, and compatibility with larger device formats.
Applications and Future Outlook
Despite rapid progress, challenges remain in achieving uniform molecular coverage, strong and durable substrate attachment, reproducible fabrication, and long-term operational stability. Weakly adsorbed molecules may desorb during processing or operation, while excessive acidity, unsuitable molecular packing, and poor precursor wettability can compromise buried interfaces. The review highlights the need for more stable molecular designs, improved surface preparation, advanced deposition methods, and better characterization of SAM assembly and interfacial structures. Addressing these issues will be essential to translate laboratory-scale efficiency gains into reliable, large-area perovskite solar modules and commercially viable tandem photovoltaic technologies.
Nano-Micro Letters
News article
Designing Efficient Inverted Perovskite Solar Cells with Self‑Assembled Monolayer Hole Transport Layers
10-Aug-2026