Role of self-assembled molecules in halide perovskite optoelectronics: An atomic-scale perspective

Metal halide perovskites have demonstrated rapid development in applications such as solar cells, photodetectors, light-emitting diodes, and lasers. Their core advantages stem from tunable bandgap, high optical absorption coefficient, low exciton binding energy, high carrier mobility, and low-cost processing. Unique electronic structure features—including strong band-edge dispersion, cross-bandgap hybridization, band-edge antibonding states, and Rashba spin splitting—form the physical foundation for their exceptional performance. Through in-depth understanding of structure-property relationships, perovskite optoelectronic devices have achieved remarkable breakthroughs: as of 2024, the power conversion efficiency of perovskite solar cells (PSCs) has exceeded 26%, while the external quantum efficiency of perovskite light-emitting diodes (PeLEDs) has surpassed 30%. Enhancing efficiency and long-term stability while reducing environmental and biological toxicity is critical for large-scale industrialization, presenting both challenges and opportunities across the entire research chain from material design to device synthesis.

PSCs and PeLEDs share similar device architectures, comprising core components such as active layers, charge transport layers, and electrodes. After over a decade of development, the chemical composition of perovskite active layers has formed a mature optimization system, while surface and interface engineering has become a key factor influencing device performance. Researchers have optimized transport layers, developing electron transport materials such as TiO₂, ZnO, SnO₂, C₆₀, and PC₆₁BM, as well as hole transport materials including Spiro-OMeTAD, NiOx, PEDOT:PSS, and PTAA. However, these materials still face challenges including high processing temperatures, low stability, interface defects, severe parasitic absorption, and high costs. In this context, self-assembled molecules (SAMs) have been successfully applied in perovskite optoelectronic devices, serving either as independent transport layers on both sides of perovskites or as modifiers for the surface of bottom transport layers or perovskite top layers.

"Recently, Professor Lijun Zhang from the School of Materials Science and Engineering, and Associate Professor Yuhao Fu from the School of Physics at Jilin University, along with collaborators, published a review article titled 'Role of Self-Assembled Molecules in Halide Perovskite Optoelectronics: An Atomic-Scale Perspective' in the National Science Review (NSR). This article systematically reviews the role of SAMs in enhancing the performance of perovskite optoelectronic devices, elucidates the underlying interface mechanisms from an atomic-scale perspective, and provides unique insights into molecular design strategies. Postdoctoral researchers Xiaoyu Wang and Xue Wang from the School of Materials Science and Engineering at Jilin University are the first authors of the paper."

The beneficial effects of SAMs on optoelectronic devices primarily originate from their atomic-scale interactions with functional layers, which can be categorized into four aspects:

1. Energy-level alignment & defect passivation: SAMs regulate interfacial energy-level alignment through dipole introduction and optimize carrier transport by passivating interface defects.
2. Surface modification & growth control: SAMs improve precursor solution wettability and enhance film uniformity by modulating surface energy and perovskite growth kinetics.
3. Stress relief & interfacial bonding: The intrinsic flexibility of SAMs and their interfacial interactions alleviate mechanical stress while strengthening interfacial adhesion.
4. Chemical stabilization: SAMs suppress detrimental chemical reactions or phase segregation via steric effects and anchoring interactions, thereby improving device chemical stability.

Based on these mechanisms, SAMs have been widely applied in single-junction/tandem PSCs and PeLEDs, emerging as a key strategy for enhancing efficiency and stability.

This review systematically examines the multidimensional roles of SAMs in perovskite optoelectronic devices and their atomic-scale physicochemical origins. It first outlines the evolutionary trajectory, molecular structural characteristics, physicochemical properties, and application modes of SAMs in devices. Subsequently, it analyzes SAM-mediated regulation of interfacial properties—including charge transport, wettability, uniformity, stress distribution, mechanical strength, and chemical stability. By summarizing atomic-scale processes underlying these effects, the review reveals the physical essence of SAMs' superior interface-modification capabilities. Finally, it discusses challenges in SAM characterization, implementation, and design, proposing corresponding solutions and future research directions.

---

---