Key Takeaways & Executive Findings
- •• Crystallization-sequence engineering enables organic solar cell modules to achieve efficiencies exceeding 18%. • The approach addresses the thickness constraint of the active layer, facilitating scalable manufacturing. • Thicker active layers are achieved without compromising efficiency, improving light harvesting and processing window. • The technique mitigates recombination and phase separation issues in thick films, enhancing charge extraction.
Abstract
Organic solar cells (OSCs) have emerged as a promising photovoltaic technology owing to their intrinsic advantages of mechanical flexibility, low density, and compatibility with solution-based fabrication. These features enable applications that are difficult to realize with rigid inorganic counterparts, including wearable electronics, portable energy systems, curved or lightweight structures, and building-integrated photovoltaics. Moreover, OSCs can be manufactured using scalable coating and printing techniques at relatively low temperatures, offering the prospect of high-throughput and cost-effective production. Despite the rapid increase in laboratory efficiencies over the past decade, transferring these advances to large-area modules remains a significant challenge. A major obstacle in OSC scale-up originates from the thickness constraint of the photoactive layer. High-efficiency devices are typically based on donor–acceptor blends forming a bulk heterojunction (BHJ), in which nanoscale phase separation ensures efficient exciton dissociation and continuous pathways for charge transport. In most state-of-the-art systems, the optimal thickness of the active layer is around 80–120 nm. Such thin films allow charges to be extracted before recombination dominates. However, films of this thickness are difficult to deposit uniformly over large areas using industrially relevant methods such as blade coating, slot-die coating, or printing. Small thickness variations can easily generate pinholes, shunts, and nonuniform electric fields, resulting in low manufacturing yield and poor operational reliability. From a practical manufacturing perspective, thicker active layers are highly desirable. Increasing the film thickness enhances light harvesting, reduces sensitivity to local defects, and widens the processing window during large-area coating. Unfortunately, simply increasing the thickness in conventional OSCs often causes a sharp decrease in power conversion efficiency. In thick films, photogenerated carriers must travel longer distances to reach the electrodes, amplifying the impact of limited mobility and trap-assisted recombination. At the same time, uncontrolled phase separation during solvent evaporation may lead to disconnected percolation networks and unfavorable vertical composition profiles, which further hinder balanced charge extraction. As a result, a fundamental co
1. Introduction
Organic solar cells (OSCs) have emerged as a promising photovoltaic technology owing to their intrinsic advantages of mechanical flexibility, low density, and compatibility with solution-based fabrication. These features enable applications that are difficult to realize with rigid inorganic counterparts, including wearable electronics, portable energy systems, curved or lightweight structures, and building-integrated photovoltaics. Moreover, OSCs can be manufactured using scalable coating and printing techniques at relatively low temperatures, offering the prospect of high-throughput and cost-effective production. Despite the rapid increase in laboratory efficiencies over the past decade, transferring these advances to large-area modules remains a significant challenge.
A major obstacle in OSC scale-up originates from the thickness constraint of the photoactive layer. High-efficiency devices are typically based on donor–acceptor blends forming a bulk heterojunction (BHJ), in which nanoscale phase separation ensures efficient exciton dissociation and continuous pathways for charge transport. In most state-of-the-art systems, the optimal thickness of the active layer is around 80–120 nm. Such thin films allow charges to be extracted before recombination dominates. However, films of this thickness are difficult to deposit uniformly over large areas using industrially relevant methods such as blade coating, slot-die coating, or printing. Small thickness variations can easily generate pinholes, shunts, and nonuniform electric fields, resulting in low manufacturing yield and poor operational reliability.
From a practical manufacturing perspective, thicker active layers are highly desirable. Increasing the film thickness enhances light harvesting, reduces sensitivity to local defects, and widens the processing window during large-area coating. Unfortunately, simply increasing the thickness in conventional OSCs often causes a sharp decrease in power conversion efficiency. In thick films, photogenerated carriers must travel longer distances to reach the electrodes, amplifying the impact of limited mobility and trap-assisted recombination. At the same time, uncontrolled phase separation during solvent evaporation may lead to disconnected percolation networks and unfavorable vertical composition profiles, which further hinder balanced charge extraction. As a result, a fundamental co
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Yunhao Cai, Hui Huang (2026). Crystallization-sequence engineering enables organic solar cell modules with efficiencies exceeding 18%. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/26020050
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Frequently Asked Questions
What is crystallization-sequence engineering in organic solar cells?
Crystallization-sequence engineering is a technique that controls the order and timing of crystallization of donor and acceptor materials in the active layer of organic solar cells. This approach optimizes the nanoscale morphology and phase separation, enabling thicker active layers without sacrificing efficiency, which is crucial for large-area module fabrication.
Why is achieving efficiencies exceeding 18% significant for organic solar cell modules?
Achieving efficiencies above 18% in organic solar cell modules is a major milestone because it demonstrates that high-performance organic photovoltaics can be scaled up from small-area lab cells to large-area modules, making them commercially viable for applications like building-integrated photovoltaics and portable electronics.
What are the main challenges in scaling up organic solar cells?
The main challenges include the thickness constraint of the active layer (typically 80-120 nm), which is difficult to deposit uniformly over large areas using industrial methods. Thicker layers often lead to reduced efficiency due to increased recombination and poor charge transport, but crystallization-sequence engineering helps overcome these issues.
How does crystallization-sequence engineering improve thick active layers?
By controlling the crystallization sequence, the technique ensures a favorable nanoscale morphology and vertical composition profile, which facilitates efficient charge transport and reduces recombination even in thicker films. This allows for better light harvesting and a wider processing window without compromising efficiency.
What are the potential applications of organic solar cells with efficiencies exceeding 18%?
Such high-efficiency organic solar cells can be used in flexible, lightweight, and semi-transparent photovoltaic devices, enabling applications like wearable electronics, portable chargers, building-integrated photovoltaics, and other curved or lightweight structures where traditional rigid solar panels are impractical.
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