Crystalline buffer layer pushes organic solar cells to 20.21 percent efficiency

by Riko Seibo

Tokyo (SPX) May 01, 2026

Researchers have achieved a power conversion efficiency of 20.21 percent in pseudo-planar heterojunction organic solar cells by introducing a crystalline polymer buffer layer that shields against solvent-induced erosion during fabrication.

The study, published in Chinese Journal of Polymer Science, addresses a persistent challenge in layer-by-layer deposition. During application of the top acceptor layer, solvents commonly cause swelling or erosion of the underlying donor layer. This disruption leads to undesirable intermixing between donor and acceptor materials, deteriorating vertical phase separation morphology, limiting charge transport efficiency, and increasing energy loss.

The research team introduced a highly crystalline polymer as a buffer layer between donor and acceptor materials. 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 preserves the structural integrity of the donor layer and maintains a well-defined heterojunction interface, which is critical for device performance.

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.

Devices incorporating the interfacial buffer layer achieved a power conversion efficiency of 19.80 percent, demonstrating clear advantages over conventional structures. By further introducing a ternary component to enhance light absorption, the efficiency was increased to 20.21 percent.

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.

Beyond performance improvements, the study provides 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 deepen the understanding of microstructural control in organic solar cells and offer 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.

Organic solar cells have attracted increasing attention as a 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 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.

Research Report: Erosion-immune Layer-by-layer Deposition Enabled by Interfacial Buffering toward 20.21%-Efficient Pseudo-Planar Heterojunction Organic Solar Cells