Acta Phys. -Chim. Sin. ›› 2026, Vol. 42 ›› Issue (11): 100253.doi: 10.1016/j.actphy.2026.100253

• ARTICLE • Previous Articles     Next Articles

Green/red dual-mode photomultiplication model organic photodetectors via adjusting charge injection direction

Shuai Zhang1, Hongfei Qu1, Lu Zhang1, Xingchao Zhao1, Luxin Zhang2, Yao Ma2, Liang Shen2, Xiaoling Ma1, Fujun Zhang1   

  1. 1 Advanced Organic Materials and Devices Laboratory, School of Physical Science and Engineering, Beijing Jiaotong University, Beijing 100044, China;
    2 State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, Jilin Province, China
  • Received:2025-12-18 Revised:2026-01-30 Accepted:2026-02-01 Published:2026-09-29
  • Contact: Liang Shen, Xiaoling Ma, Fujun Zhang E-mail:shenliang@jlu.edu.cn;xlma2@bjtu.edu.cn;fjzhang@bjtu.edu.cn

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Abstract: Dual-mode photomultiplication model organic photodetectors (PMOPDs) were fabricated with an architecture of poly (9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT):poly [4,8-bis(5-(2-ethylhexyl) thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno [3,4-b] thiophene-)-2-carboxylate-2-6-diyl] (PTB7-Th) (3 : 1, w/w)/Glass/indium tin oxide (ITO)/poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-5,5'-bis(2,2'-thiophene)-2,6-naphthalene-1,4,5,8-tetracaboxylic-N,N'-di(2-ethylhexyl)imide] (PNDIT-F3N)/poly(3-hexylthiophene) (P3HT):[6,6]-phenylC71-butyric acid methyl ester (PC71BM) (100 : 1, w/w)/Aluminum (Al). To modulate the optical field distribution, an external layer of F8BT:PTB7-Th acts as an organic filter layer (OFL) in PMOPDs. Dual-mode characteristics can be achieved from PMOPDs under forward and reverse bias, which is individually determined by the trapped electron distribution near ITO and Al electrode. The PMOPDs achieve a green narrowband response under 8 V bias, with peak external quantum efficiency (EQE) of 8880% at 545 nm and full width at half maximum (FWHM) of 85 nm. Conversely, a red narrowband response is registered under -8 V bias of PMOPDs, centered at 620 nm with peak EQE of 750% and FWHM of 60 nm. The operating mechanism for the switchable mode of PMOPDs involves the modulation of trapped electron distribution, which shifts between the vicinity of ITO electrode under forward bias and Al electrode under reverse bias. A photoplethysmography (PPG) measurement system based on the optimal dual-mode PMOPDs was developed to enable the successful monitoring of heart rate across different conditions. The velocity plethysmography and acceleration plethysmography can be obtained from original PPG signals to estimate arteriosclerosis for vascular disease diagnosis.

Key words: Photomultiplication, Dual-mode, Narrowband response, Heart rate monitoring