Hot carrier-enhanced interlayer electron–hole pair multiplication in 2D semiconductor heterostructure photocells*

Two-dimensional heterostructures composed of atomically thin transition metal dichalcogenides (TMDs) provide an excellent opportunity to study electron–hole (e–h) pair multiplication. Here, we report the highly efficient multiplication of interlayer e–h pairs in 2D semiconductor heterostructure photocells composed of 2L-WSe₂ and 1L-MoSe₂. The carrier multiplication process, which is made more efficient through hot carrier transfer at the interface between WSe₂ and MoSe₂, can be utilized to significantly increase the photoresponse in these TMD heterojunction photocells. By exploiting this highly efficient interlayer e–h pair multiplication process, we demonstrate near-infrared optoelectronic devices that exhibit 350% enhancement of the optoelectronic responsivity at microwatt power levels. Our findings, which demonstrate efficient carrier multiplication in TMD-based optoelectronic devices, make 2D semiconductor heterostructures viable for a new class of ultra-efficient photodetectors based on layer-indirect e–h excitations.