Photojunction Field-Effect Transistor Based on a Colloidal Quantum Dot Absorber Channel Layer

Valerio Adinolfi, Illan J. Kramer, André J. Labelle, Brandon R. Sutherland, S. Hoogland, Edward H. Sargent

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

Abstract

© 2015 American Chemical Society. The performance of photodetectors is judged via high responsivity, fast speed of response, and low background current. Many previously reported photodetectors based on size-tuned colloidal quantum dots (CQDs) have relied either on photodiodes, which, since they are primary photocarrier devices, lack gain; or photoconductors, which provide gain but at the expense of slow response (due to delayed charge carrier escape from sensitizing centers) and an inherent dark current vs responsivity trade-off. Here we report a photojunction field-effect transistor (photoJFET), which provides gain while breaking prior photoconductors' response/speed/dark current trade-off. This is achieved by ensuring that, in the dark, the channel is fully depleted due to a rectifying junction between a deep-work-function transparent conductive top contact (MoO3) and a moderately n-type CQD film (iodine treated PbS CQDs). We characterize the rectifying behavior of the junction and the linearity of the channel characteristics under illumination, and we observe a 10 μs rise time, a record for a gain-providing, low-dark-current CQD photodetector. We prove, using an analytical model validated using experimental measurements, that for a given response time the device provides a two-orders-of-magnitude improvement in photocurrent-to-dark-current ratio compared to photoconductors. The photoJFET, which relies on a junction gate-effect, enriches the growing family of CQD photosensitive transistors.
Original languageEnglish (US)
Pages (from-to)356-362
Number of pages7
JournalACS Nano
Volume9
Issue number1
DOIs
StatePublished - Jan 13 2015
Externally publishedYes

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