Highly Efficient Carrier Multiplication in van der Waals layered Materials

TL;DR

This paper demonstrates ultra-efficient carrier multiplication in van der Waals layered materials, achieving nearly 100% conversion efficiency and low threshold energy, promising for advanced solar cell applications.

Contribution

It introduces a new class of vdW layered materials exhibiting near-perfect carrier multiplication efficiency starting at the energy conservation limit.

Findings

Carrier multiplication begins at the energy conservation limit.

Achieved a low threshold energy of twice the bandgap.

Near 100% quantum yield in vdW materials.

Abstract

Carrier multiplication (CM), a photo-physical process to generate multiple electron-hole pairs by exploiting excess energy of free carriers, is explored for efficient photovoltaic conversion of photons from the blue solar band, predominantly wasted as heat in standard solar cells. Current state-of-the-art approaches with nanomaterials have demonstrated improved CM but are not satisfactory due to high energy loss and inherent difficulties with carrier extraction. Here, we report ultra-efficient CM in van der Waals (vdW) layered materials that commences at the energy conservation limit and proceeds with nearly 100% conversion efficiency. A small threshold energy, as low as twice the bandgap, was achieved, marking an onset of quantum yield with enhanced carrier generation. Strong Coulomb interactions between electrons confined within vdW layers allow rapid electron-electron scattering to prevail over electron-phonon scattering. Additionally, the presence of electron pockets spread over momentum space could also contribute to the high CM efficiency. Combining with high conductivity and optimal bandgap, these superior CM characteristics identify vdW materials for third-generation solar cell.