Dual-Junction Photovoltaic Detectors for Performance Improvement

Hybrids combining with different materials, dimensions, and intrinsic characters have brought promising opportunities for new physics and device functions. In this work, the semimetal (1T′-MoTe2), p-type (WSe2), and n-type (MoS2) 2-D semiconductors have been integrated layer-by-layer, enabling the dual-junction photovoltaic detectors comprising of Schottky and p-n junction at the 1T′-MoTe2/WSe2 and WSe2/MoS2 heterogeneous interface, respectively. Due to the synergistic effect of the dual junction, the photo-excited electrons and holes can be efficiently separated and collected, resulting in a high photodetection performance with a responsivity (R) of 102 mA/W, detectivity (
${D}^{\ast } $
) of
$7 \times 10^{{10}}$
Jones, and
${I}_{\text {on}}$
/
${I}_{\text {off}}$
ratio of
$4.2 \times 10^{{4}}$
at zero bias under 635-nm illumination; all these parameters are much improved compared to that in single-junction-based device. Significantly, the values of R and
${I} _{\text {on}}$
/
${I} _{\text {off}}$
ratio of 1T′-MoTe2/WSe2/MoS2 are improved by about 20 times compared to 1T′-MoTe2/WSe2. This work proposes a dual-junction device architecture by connecting Schottky and p-n junctions in series, favorable for the improvement in photodetection performance.