Key Takeaways & Executive Findings
- •• • The optimal ternary UV-OPD achieves a peak external quantum efficiency (EQE) of 78.29% at 340 nm, with EQE exceeding 53% across the 280–400 nm range, representing a significant improvement over conventional UV photodetectors. • • A high responsivity of 214.68 mA/W at 340 nm is attained, coupled with a rapid response time of 2.6/2.1 μs, marking the best reported combination of responsivity and speed in the UV region. • • Replacing conventional glass/ITO substrates with a quartz substrate and PH1000 electrode enhances UV transmittance, directly addressing the absorption losses that previously limited UV-OPD performance. • • The integration of the ternary blend PM6:Y6:PC71BM as the active layer is critical for achieving high UV absorption and efficient charge generation, enabling the device to operate effectively across the UV-A and UV-B spectral regions.
Abstract
Excessive ultraviolet (UV) radiation poses significant risks to human health, necessitating highly sensitive detection systems. Organic photodetectors (OPDs) offer high sensitivity and tunable spectral response, but their UV performance is constrained by conventional glass/indium tin oxide (ITO) substrates and electrodes, and insufficient photoactive layer responsivity. Here, we report high-performance UV-OPDs achieved through UV-transparent window and active-layer optimization. Replacing glass/ITO with a UV-transparent window comprising a quartz substrate and PH1000 electrode enhances UV transmittance. Integrating the high UV-responsive blend PM6:Y6:PC71BM as the active layer, the optimal ternary UV-OPD exhibits external quantum efficiency (EQE) exceeding 53% across 280–400 nm, with a peak EQE of 78.29% and responsivity of 214.68 mA/W at 340 nm, alongside a rapid response time of 2.6/2.1 μs. This performance represents the best combination of responsivity and response time reported to date in the UV region. We demonstrate the potential of these UV-OPDs for outdoor real-time UV monitoring. This work presents a promising strategy for developing high-performance UV-OPDs through transparent substrate and electrode engineering, and active-layer optimization.
1. Introduction
Excessive ultraviolet (UV) radiation from the sun poses significant health risks, including skin cancer and eye disorders, driving the need for reliable, real-time UV monitoring. Conventional Si-based photodetectors suffer from poor UV responsivity due to low absorption coefficients, while wide-bandgap semiconductors like GaN and ZnO offer better performance but are hindered by high manufacturing costs, lack of mechanical flexibility, and slow response times (milliseconds to seconds). These limitations create a critical bottleneck for wearable and portable health monitoring applications.
Organic photodetectors (OPDs) present a compelling alternative, offering high UV absorption, mechanical flexibility, and low-cost solution processing. However, their UV performance has been constrained by the use of conventional glass/ITO substrates and electrodes, which absorb significant UV light, and by photoactive layers with insufficient responsivity. This work addresses these bottlenecks by engineering a UV-transparent window using quartz and PH1000 electrode, and by optimizing the active layer with a ternary blend PM6:Y6:PC71BM. This dual approach expands the spectral window and dramatically enhances device performance, achieving record responsivity and response speed in the UV region, thereby enabling practical outdoor health monitoring.
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Zhanzhao Yin, Yu Zhu, Hanzhe Shi, Tingting Guo, Ruiman Han, Yongsheng Liu, Yongsheng Chen (2026). Ultra-sensitive ultraviolet organic photodetectors enabled by an expanded spectral window for health monitoring. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4183-3
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Frequently Asked Questions
What are the specific performance metrics of the UV-OPD, and how do they compare to state-of-the-art inorganic UV photodetectors?
The optimal ternary UV-OPD achieves a peak EQE of 78.29% at 340 nm, a responsivity of 214.68 mA/W, and a response time of 2.6/2.1 μs. These metrics represent the best combination of responsivity and speed reported for UV OPDs to date. In comparison, GaN-based photodetectors typically exhibit responsivities around 100 mA/W with response times in the millisecond range, while ZnO-based devices often have slower response times. The OPD's fast response and high sensitivity make it suitable for real-time monitoring applications.
How does the replacement of glass/ITO with quartz/PH1000 improve UV performance, and what are the trade-offs in terms of cost and scalability?
Quartz substrates and PH1000 electrodes offer superior UV transmittance compared to glass/ITO, which absorbs a significant portion of UV light. This enhancement allows more UV photons to reach the active layer, directly increasing EQE and responsivity. While quartz and PH1000 may be more expensive than conventional materials, the performance gains justify the cost for specialized applications. The solution-processable nature of PH1000 and the availability of quartz substrates suggest potential for scalable manufacturing, though further cost analysis is needed for mass production.
What is the role of the ternary blend PM6:Y6:PC71BM in achieving high UV responsivity, and how does it compare to binary blends?
The ternary blend combines a wide-bandgap donor (PM6) with a narrow-bandgap acceptor (Y6) and a fullerene derivative (PC71BM) to broaden the absorption spectrum and enhance charge generation. This composition optimizes the morphology and energy levels, leading to efficient exciton dissociation and charge transport. The ternary blend achieves a peak EQE of 78.29% in the UV region, outperforming binary blends that typically have narrower absorption and lower EQE. The specific role of PC71BM is to improve electron mobility and reduce recombination, as evidenced by the high responsivity and fast response time.
What are the long-term stability and operational lifetime of these UV-OPDs under continuous UV exposure, and what encapsulation strategies are recommended?
The paper does not provide explicit long-term stability data. However, organic photodetectors generally suffer from degradation under UV exposure due to photo-oxidation. To ensure practical deployment, encapsulation with UV-blocking or barrier materials is recommended. The use of quartz substrates and PH1000 electrodes may offer some inherent stability, but further studies are needed to quantify operational lifetime under continuous UV irradiation. For health monitoring applications, devices must maintain performance over extended periods, so accelerated aging tests are essential.
How does the response time of 2.6/2.1 μs compare to the requirements for real-time UV monitoring, and what limits the speed?
A response time of 2.6/2.1 μs is exceptionally fast, far exceeding the requirements for real-time UV monitoring, which typically operates at frequencies below 1 kHz. This speed is limited by the charge carrier mobility and the RC time constant of the device. The high mobility of the ternary blend and the optimized electrode geometry contribute to the fast response. Such speed enables not only steady-state monitoring but also detection of fast UV pulses, which could be useful in applications like UV communication or pulsed-light sensing.
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