Organic Photoelectrochemical Transistors for Bioelectronics Applications

  • Latifah Almulla

Student thesis: Master's Thesis


An organic photoelectrochemical transistor (OPECT) is an electrochemical transistor in which the output current is controlled by light. OPECTs show increased transconductance upon light exposure, thus enhancing the sensitivity and signal-to-noise ratio when the transistor is used as a biosensor. However, to make an organic electrochemical transistor photosensitive, it is necessary to integrate photoactive materials into the device, which often requires the use of additional metals, sophisticated nanostructures, and complex synthetic approaches. Moreover, current OPECT devices are only responsive to the visible region, and their use in the near-infrared range has not been investigated yet. This thesis explores the possibility of building an OPECT by use of a single photoactive material that acts both as the photoactive gate and the channel material to simplify OPECT design. We screen photoelectrochemical properties of water-compatible, n-type soft semiconducting polymers and their performance in OPECT architectures with potential applications at the biological interface. Moreover, we explore another organic material and device architecture to render OPECTs suitable for near-infrared (NIR) detection. We demonstrate the use of the NIR sensitive organic film in capturing photoplethysmography signals, and we offer our perspective on how these materials and devices could advance the operation of existing bioelectronic devices. The main contributions of this thesis are organized into five chapters: Chapter 1 provides a background on photodiodes in general, focusing on solid-state and electrolyte-gated phototransistors. Chapter 2 presents the methods used for characterizing the materials, fabricating the devices, and evaluating their performance. Chapter 3 showcases the development of OPECTs based on n-type polymeric mixed conductors. Chapter 4 introduces a material with absorption in NIR and demonstrates its use in a photoelectrochemical transistor. Chapter 5 summarizes the main findings of this thesis and provides an outlook for future directions.
Date of AwardJul 2023
Original languageEnglish (US)
Awarding Institution
  • Biological, Environmental Sciences and Engineering
SupervisorSahika Inal (Supervisor)

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