Toward Faster Organic Photodiodes: Tuning of Blend Composition Ratio

Siddhartha Saggar, Stephen Sanderson, Desta Gedefaw, Xun Pan, Bronson Philippa, Mats R. Andersson, Shih Chun Lo, Ebinazar B. Namdas

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


The ability of a light-sensor to detect fast variation in incident light intensity is a vital feature required in imaging and data transmission applications. Solution-processed bulk heterojunction (BHJ) type organic photodiodes (OPDs) have gone through key developments, including dark current mitigation and longer linear dynamic range. In contrast, there has been less focus on increasing OPD response speed (f–3dB). Here, bulk heterojunction OPDs based on electron-donating polymer poly[thiophene-2,5-diyl-alt-5,10-bis((2-hexyldecyl)oxy)dithieno[3,2-c:3′,2′-h][1,5]naphthyridine-2,7-diyl] (or PTNT) and electron-accepting phenyl-C71-butyric acid methyl ester (or PC71BM) are reported. The intrinsic charge transport characteristics required for fast speed OPDs are discussed, and an analytical model for the same is developed. The OPDs present 0.8 MHz f–3dB under no applied voltage bias for a typical blend ratio of 1:1 by weight. It is shown that balanced electron and hole mobility is a critical criterion for faster speed OPDs, which can be realized by tuning the composition ratio of the bulk heterojunction. By tuning PTNT and PC71BM blend ratio, the f–3dB was successfully raised by more than quadruple to 4.5 MHz. The findings provide a tool to set device architecture for faster next-generation light sensors.

Original languageEnglish
Article number2010661
Number of pages8
JournalAdvanced Functional Materials
Issue number19
Publication statusPublished - 10 May 2021


  • cutoff frequency
  • polymer photodiodes
  • response speed


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