Giant polarization-dependent bulk photovoltaic effect in bandgap-tunable TeSe

The bulk photovoltaic effect (BPVE), capable of surpassing the Shockley–Queisser limit, offers promising routes for high-efficiency energy harvesting. Alloy engineering provides a powerful means to tailor this phenomenon. Herein, high-quality composition-tunable TeSe crystals are synthesized via chemical vapor transport. These crystals exhibit p-type conductivity, with electrical conductivity and hole mobility increasing monotonically with Te content. Optimal transistor performance was achieved at Te = 0.4, where an on/off ratio of 103 and a hole mobility of 4 cm2 V−1 s−1 were obtained. First-principles calculations reveal a tunable indirect bandgap from 0.27 to 0.62 eV. A pronounced BPVE is observed over an ultra-broadband spectrum (275–1920 nm), and the response edge redshifts with increasing Te concentration. The Te0.8Se0.2-based device achieves a remarkable short-circuit current density (Jsc) of 7.4 mA/cm2 under 1310 nm illumination, surpassing that of most reported materials by several orders of magnitude, being only slightly lower than that of Te nanosheets. Furthermore, the system exhibits strong polarization sensitivity, evidenced by a high dichroic ratio of 4.36 at 1550 nm. Demonstrated polarization imaging assisted by deep learning underscores the potential of TeSe crystals as a versatile platform for high-performance, polarization-sensitive BPVE photodetectors.