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Elucidating the Detectivity Limits in Shortwave Infrared Organic Photodiodes
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2018-03-09 , DOI: 10.1002/adfm.201800391
Zhenghui Wu 1 , Weichuan Yao 1 , Alexander E. London 2 , Jason D. Azoulay 2 , Tse Nga Ng 1
Affiliation  

While only few organic photodiodes have photoresponse past 1 µm, novel shortwave infrared (SWIR) polymers are emerging, and a better understanding of the limiting factors in narrow bandgap devices is critically needed to predict and advance performance. Based on state‐of‐the‐art SWIR bulk heterojunction photodiodes, this work demonstrates a model that accounts for the increasing electric‐field dependence of photocurrent in narrow bandgap materials. This physical model offers an expedient method to pinpoint the origins of efficiency losses, by decoupling the exciton dissociation efficiency and charge collection efficiency in photocurrent–voltage measurements. These results from transient photoconductivity measurements indicate that the main loss is due to poor exciton dissociation, particularly significant in photodiodes with low‐energy charge‐transfer states. Direct measurements of the noise components are analyzed to caution against using assumptions that could lead to an overestimation of detectivity. The devices show a peak detectivity of 5 × 1010 Jones with a spectral range up to 1.55 µm. The photodiodes are demonstrated to quantify the ethanol–water content in a mixture within 1% accuracy, conveying the potential of organics to enable economical, scalable detectors for SWIR spectroscopy.

中文翻译:

阐明短波红外有机光电二极管的检出限

尽管只有很少的有机光电二极管具有超过1 µm的光响应,但是正在出现新型的短波红外(SWIR)聚合物,因此,对窄带隙器件中的限制因素有更好的了解,才能预测和提高性能。基于最新的SWIR体异质结光电二极管,这项工作演示了一个模型,该模型说明了窄带隙材料中光电流对电场的依赖性不断提高。通过在光电流-电压测量中将激子离解效率和电荷收集效率解耦,该物理模型提供了一种简便的方法来确定效率损失的起因。瞬态光电导率测量的这些结果表明,主要损耗是由于激子离解差,在具有低能量电荷转移状态的光电二极管中尤为重要。分析了噪声成分的直接测量值,以警告不要使用可能导致过高估计检测率的假设。器件显示出5×10的峰值检测率10 Jones的光谱范围高达1.55 µm。光电二极管经证实可以在1%的精度内对混合物中的乙醇-水含量进行定量,从而传达出有机物的潜力,从而可以实现经济,可扩展的SWIR光谱检测器。
更新日期:2018-03-09
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