# Tianjin University develops organic phototransistor array with 2,920 dichroic ratio

- Published: 2026-11-07 03:10 UTC
- Section: Machines & Making › Electronics
- Tags: organic single crystals, neuromorphic polarization vision, dichroic ratio, polyvinyl alcohol electret, photogating effect, Tianjin University
- URL: https://realtech.media/news/rt-9eca98f9d701c236e9825339_tianjin_university_develops/

**Researchers created a scalable organic crystal array for neuromorphic polarization vision, reaching an energy consumption of 1 aJ per synaptic event.**

![Tianjin University develops organic phototransistor array with 2,920 dichroic ratio](https://realtech.media/media/2026/11/9b0ce36a60743247.jpg)
*Raimond Spekking, Wikimedia Commons, CC BY-SA 4.0*

Researchers from Tianjin University reported an electret-mediated biphasic dip-coating technique to fabricate large-area organic phototransistors for neuromorphic polarization vision, according to a study published in National Science Review. The platform couples ultrathin, highly oriented few-layer organic single crystals with an in-situ polyvinyl alcohol (PVA) electret layer, enabling synchronized light sensing, memory, and preprocessing within a single device architecture [1].

## Scalable growth and charge trapping

Polyvinyl alcohol plays a dual role during the dip-coating process. Its amphiphilic structure regulates interfacial nucleation and stabilizes molecular mass transport, allowing uniform organic single crystals to grow across centimeter-scale areas [1]. Simultaneously, the underlying hydroxyl-rich PVA layer functions as an electret, capturing photoexcited electrons and inducing a photogating effect that nonlinearly magnifies the material's optical anisotropy.

Individual phototransistors reached a dichroic ratio of 2,920, which is more than three orders of magnitude above the pristine crystal's intrinsic limit [1]. In a fully operational 7×7 transistor array, the average dichroic ratio reached 2,400 with a standard deviation of approximately 200 and a coefficient of variation of 7.3%.

## Synaptic plasticity and visual recognition

The charge-trapping mechanism also establishes pronounced synaptic behavior. The system recorded a paired-pulse facilitation index of 6,594%, supported a photocurrent modulation range exceeding five orders of magnitude, and operated at an estimated energy consumption of approximately 1 aJ per synaptic event [1].

To demonstrate image processing, the authors evaluated a 5×5 sensor array that recorded and retained polarization-dependent optical patterns. In a semantic recognition test using polarization angles of 0, 45, 90, and 135 degrees across five fruit types, hardware-derived convolution kernels achieved a classification accuracy of 95.25% by fusing the multi-angle datasets [1].

## Sources

1. [National Science Review](https://doi.org/10.1093/nsr/nwag625)
2. [EurekAlert](https://www.eurekalert.org/news-releases/1150910)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-9eca98f9d701c236e9825339_tianjin_university_develops/