A novel approach for designing efficient broadband photodetectors

Photodetectors (PDs) are the technical functional components for capturing and converting ultraviolet (UV) to near-infrared (NIR) photons into electronic outputs. The broadband optical detection ability, especially from UV to NIR range, is critical for the applications including medical monitoring, video imaging, optical communication, and civil engineering. Generally, the commercial silicon PDs present the relatively broad wavelength response range from 400-1100 nm, but usually suffers from high cost and low detectivity, especially in UV region. Solution-processable broadband PDs based on soluble materials have numerous advantages of low cost, simple preparation, and high sensitivity, which has becoming the next generation of new detectors.

In a new paper published in Light Science & Application, a team of scientists, led by Professors Hongwei Song from State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, China, and Professors Wen Xu Key Laboratory of New Energy and Rare Earth Resource Utilization of State Ethnic Affairs Commission, Dalian Minzu University and co-workers have explored a novel approach for designing efficient broadband photodetectors expanding from deep ultraviolet to near infrared. Herein, there employ CsPbCl₃:Cr³⁺,Ce³⁺,Mn²⁺ PQDs ultraviolet luminescent concentrators  (Cr/Ce/Mn-LC), iodine based perovskite quantum dots (PQDs), and organic bulk heterojunction (BHJ) as the UV, visible, and near infrared (NIR) photosensitive layers, respectively, to construct a broadband heterojunction PD. In this work, unique broadband PDs with the response range of 200-1000 nm and the D* value reaching of 1.14×10¹² at 260 nm and 2.46×10¹² at 460 nm and 1.85×10¹² at 860 nm based on doped PQDs and an organic bulk heterojunction and Cr/Ce/Mn-LC were reported. Compared to the previous broadband perovskite PDs, the device exhibits excellent performances with the relatively wide response, high responsivity and detectivity especially in UV and NIR regions, and good stability, which exceeds the most results of the previous reports. These scientists summarize the operational principle of their broadband PDs:

“Firstly, experimental and theoretical results reveal that optoelectronic properties and stability of CsPbI₃ PQDs are significantly improved through Er³⁺ doping, owing to the reduced defect density, improved charge mobility, and increased formation energy and tolerance factor etc. The narrow bandgap of CsPbI₃:Er³⁺ PQDs serves as visible photosensitive layer of PD. Secondly, considering the matchable energy band gap, the BHJ (BTP-4Cl : PBDB-TF) is selected as to NIR absorption layer to fabricate the hybrid structure with CsPbI₃:Er³⁺ PQDs. Thirdly, UV Cr/Ce/Mn-LC convert the UV light (200-400 nm) to visible light (400-700 nm), which further absorb by CsPbI₃:Er³⁺ PQDs.”  

“In contrast with other perovskite PDs and commercial Si PDs, our PD presents relatively wide response range and high detectivity especially in UV and NIR regions (two orders of magnitude increase that of commercial Si PDs). Furthermore, the PD also demonstrates significantly enhanced air- and UV- stability, and the photocurrent of the device maintains 81.5% of the original one after 5000 cycles.” they added.

“This work highlights a new attempt for designing broadband PDs, which has application potential in optoelectronic devices.”the scientists forecast.

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