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Abstract Given the surpassing of the Shockley-Quiesser efficiency limit in conventional p-n junction photovoltaic effect, bulk photovoltaic effect (BPVE) has garnered significant research interest. However, the BPVE primarily focuses on a narrow wavelength range, limiting its potential applications. Here we report a giant infrared bulk photovoltaic effect in tellurene (Te) for broad-spectrum neuromodulation. The generated photocurrent in uniformly illuminated Te excludes other photoelectric effects and is attributed to the BPVE. The bulk photovoltaic wavelength in Te spans a wide range from the ultraviolet (390 nm) to the mid-infrared (3.8 µm). Moreover, the photocurrent density of 70.4 A cm−2 under infrared light simulation outperforms that in previous ultraviolet and visible semiconductors as well as infrared semimetals. Te attached to the dendrites or somata of the cortical neurons successfully elicit action potentials under broad-spectrum light irradiation. This work lays the foundation for the further development of infrared BPVE in narrow bandgap materials.

Abstract Avalanche or carrier-multiplication effect, based on impact ionization processes in semiconductors, has a great potential for enhancing the performance of photodetector and solar cells. However, in practical applications, it suffers from high threshold energy, reducing the advantages of carrier multiplication. Here, we report on a low-threshold avalanche effect in a stepwise WSe2 structure, in which the combination of weak electron-phonon scattering and high electric fields leads to a low-loss carrier acceleration and multiplication. Owing to this effect, the room-temperature threshold energy approaches the fundamental limit, E thre ≈ E g, where E g is the bandgap of the semiconductor. Our findings offer an alternative perspective on the design and fabrication of future avalanche and hot-carrier photovoltaic devices.