Photodetection and imaging

We have developed novel detectors for short-wave infrared light², as well as infrared³ and terahertz light⁴. Recently, we used twisted 2D materials to realize a cutting-edge ultra-broadband photodetector⁵. This innovative device demonstrates remarkable efficiency in detecting light across a wide spectrum, ranging from terahertz with a wavelength of 100 micrometers (equivalent to 3 THz), to near-infrared at 2 micrometers (or 150 THz). This breakthrough was achieved by stacking two layers of bilayer graphene, which resulted in a small bandgap perfect for broadband photon detection. Pushing the boundaries of this technology, the group has now extended these principles to sensitive and even single-photon detection in the infrared-terahertz spectrum, a frontier that holds potential for groundbreaking commercial applications as no such solutions currently exist in the market. 

Applications and Impact on society 

We have spearheaded the creation of the world's first "graphene digital camera," which incorporates over 100,000 graphene-based photodetectors along with CMOS circuitry⁶. This camera operates for visible and shortwave infrared light, offering functionalities that include day and night vision, the ability to see through fog, and the capability to analyze the chemical composition of food, liquids, and gases. In 2020, Qurv Technologies (Qurv.tech) spun out of ICFO but still in close collaboration. It commercializes graphene-based image sensors for use in autonomous vehicles, robotics, and security systems. 

We have also developed semi-transparent image sensors for eye-tracking⁷ and flexible sensing technologies, such as a compact patch that can monitor heart rate and blood oxygen saturation levels⁸.

Future 

Our aim is to keep advancing the limits of detection capabilities through the use of novel ideas and entirely new approaches to photodetection. Layered and twisted materials present a virtually infinite range of possibilities as a new materials platform, providing us with the versatility to create the desired properties as needed. 

References: 

1. Akinwande, D. et al. Graphene and two-dimensional materials for silicon technology. Nature 573, 507–518 (2019).
2. Konstantatos, G. et al. Hybrid graphene quantum dot phototransistors with ultrahigh gain. Nature Nanotechnology 7, 363–368 (2012).
3. Castilla, S. et al. Plasmonic antenna coupling to hyperbolic phonon-polaritons for sensitive and fast mid-infrared photodetection with graphene. Nature communications 11, 1–7 (2020).
4. Castilla, S. et al. Fast and Sensitive Terahertz Detection Using an Antenna-Integrated Graphene pn Junction. Nano Letters 19, 2765–2773 (2019).
5. Agarwal, H. et al. Ultra-broadband photoconductivity in twisted graphene heterostructures with large responsivity. Nat. Photon. (2023) doi:10.1038/s41566-023-01291-0.
6. Goossens, S. et al. Broadband image sensor array based on graphene-CMOS integration. Nature Photonics 11, 366–371 (2017).
7. Mercier, G. et al. Semitransparent Image Sensors for Eye-Tracking Applications. ACS Photonics acsphotonics.3c00473 (2023) doi:10.1021/acsphotonics.3c00473.
8. Polat, E. O. et al. Flexible graphene photodetectors for wearable fitness monitoring. Science Advances 5, (2019).