Current-voltage characteristic and shot noise of shift current photovoltaics

TL;DR

This paper theoretically analyzes the current-voltage behavior and shot noise in shift current photovoltaics, highlighting the roles of band velocity differences and relaxation time, and proposes Landau levels as promising energy conversion candidates.

Contribution

It reveals how group velocity differences and relaxation time influence shift current I-V characteristics and shot noise, suggesting design strategies for improved photovoltaic efficiency.

Findings

I-V characteristic and shot noise depend on velocity difference and relaxation time.

Shift current is independent of these parameters, allowing optimization.

Landau levels in 2D systems are promising for energy conversion.

Abstract

We theoretically study the current-voltage relation, $I-V$ characteristic, of the photovoltaics due to the shift current, i.e., the photocurrent generated ${\it without}$ the external dc electric field in noncentrosymmetric crystals through the Berry connection of the Bloch wavefunctions. We find that the $I-V$ characteristic and shot noise are controlled by the difference of group velocities between conduction and valence bands, i.e., $v_{11}-v_{22}$, and the relaxation time $\tau$. Since the shift current itself is independent of these quantities, there are wide possibilities to design it to maximize the energy conversion rate and also to suppress the noise. We propose that the Landau levels in noncentrosymmetric two-dimensional systems are the promising candidate for energy conversion.