As global demand for sustainable energy continues to rise, organic solar cells (OSCs) have attracted increasing attention as a promising next-generation photovoltaic technology, owing to their lightweight nature, mechanical flexibility, and compatibility with large-area solution processing.
Among various device architectures, pseudo-planar heterojunction (PPHJ) structures fabricated via layer-by-layer deposition have emerged as an effective strategy for improving both efficiency and stability. This approach enables a more controlled vertical phase separation morphology, which is essential for efficient charge generation and transport.
However, a persistent challenge in layer-by-layer fabrication lies in solvent-induced damage. During the deposition of the top acceptor layer, commonly used solvents can cause swelling or erosion of the underlying donor layer. This disruption leads to undesirable intermixing between donor and acceptor materials, deteriorating the vertical phase separation morphology, limiting charge transport efficiency, and increasing energy loss.
A recent study published in Chinese Journal of Polymer Science, titled "Erosion-immune Layer-by-layer Deposition Enabled by Interfacial Buffering toward 20.21%-Efficient Pseudo-Planar Heterojunction Organic Solar Cells," presents an effective interfacial buffering strategy to address this issue. By introducing a highly crystalline polymer buffer layer between donor and acceptor materials, the researchers achieved a high power conversion efficiency of 20.21%, among the highest reported for PPHJ organic solar cells.
In-depth Analysis: Interfacial Buffering for Morphology and Charge Optimization
Constructing an Erosion-Resistant Interface via Crystalline Networks
The core innovation of this work lies in a simple yet effective interfacial engineering approach: incorporating a highly crystalline polymer as a buffer layer between the donor and acceptor layers. Experimental results show that this buffer layer forms a dense crystalline fibrillar network, which acts as an effective barrier against solvent penetration during subsequent processing.
By mitigating solvent-induced erosion, the buffer layer helps preserve the structural integrity of the donor layer and maintains a well-defined heterojunction interface, which is critical for device performance.
Optimizing Vertical Phase Separation and Charge Transport
Compared with conventional binary systems, the buffered architecture significantly improves the vertical phase separation morphology of the active layer. The introduction of the buffer layer enhances molecular packing and promotes a more distinct gradient distribution between donor and acceptor components.
This optimized microstructure facilitates more efficient charge transport pathways while reducing interfacial defects. As a result, non-radiative recombination losses are suppressed, and exciton dissociation becomes more efficient, contributing to improved overall device performance.
From 19.80% to 20.21%: Performance Enhancement through Structural Design
Devices incorporating the interfacial buffer layer achieved a power conversion efficiency of 19.80%, demonstrating clear advantages over conventional structures. By further introducing a ternary component to enhance light absorption, the efficiency was increased to 20.21%.
This performance ranks among the highest reported efficiencies for pseudo-planar heterojunction organic solar cells and highlights the effectiveness of interfacial buffering in improving device functionality.
Scientific Significance and Future Perspectives
Beyond performance improvements, this study provides valuable insights into the role of interfacial engineering in controlling morphology evolution during layer-by-layer processing. The combination of physical blocking and structural regulation offered by the crystalline buffer layer effectively addresses key challenges associated with solvent compatibility in high-performance organic photovoltaic systems.
These findings not only deepen the understanding of microstructural control in organic solar cells but also offer useful guidance for the future design of high-efficiency and scalable photovoltaic devices. The interfacial buffering strategy represents a promising direction for advancing the development of flexible and solution-processed solar energy technologies.
DOI: https://doi.org/10.1007/s10118-025-3500-x
Chinese Journal of Polymer Science (CJPS) is a monthly journal published in English and sponsored by the Chinese Chemical Society and the Institute of Chemistry, Chinese Academy of Sciences. CJPS is a peer-reviewed journal dedicated to the timely publication of original research ideas and results in the field of polymer science. The issues may carry regular articles, rapid communications and as well as feature articles. As a leading polymer journal in China published in English, CJPS reflects the new achievements obtained in various laboratories of China. CJPS also includes papers submitted by scientists of different countries and regions outside of China, reflecting the international nature of the journal.
