Photocurrent enhancement at two distinct wavelengths in vertically-aligned quantum dot solar cell

Abstract

Quantum dot (QD) devices show better structural stability among various photovoltaic technologies, including silicon, organic, and thin film solar cells. The QD-based solar cells emerge as promising candidates because of their unique characteristics, such as variable size and tunable band gap. For instance, symmetrically distributed impurities in QDs induce the formation of an intermediate band (IB) in solar cells, which allows the cell to absorb photons with energy lower than the bandgap. This absorption in QD-IBSC generates more electricity by increasing carrier concentration, enhancing photo-generated current, and achieving higher power conversion efficiency (PCE). The primary aim of this study is to investigate the structural properties and efficiency of novel vertically-aligned quantum dot solar cell structure. Furthermore, this paper explores the enhancement of photocurrent (PC) at two distinct wavelengths, specifically at 800 nm and 1300 nm, within the structure of a vertically-aligned quantum dot solar cell. A 3D-finite element method solver has been employed to simulate the proposed solar cell structure. Additionally, it studies the effects of voltage varying from 0 V to 0.7 V versus carrier concentration within a vertically-aligned quantum dot solar cell, revealing that higher voltage values correspond to increased carrier concentration. Results show that at P_800, the PCE of the solar cell approaches 37.7 %, compared to P₁₃₀₀. The analysis of QD state occupancy reveals a decrease in occupation at higher values of incident light intensities. The increment in PC generation for simultaneous excitation of QDs with both wavelengths is attributed to enhancing the two-step, two-photon absorption (TS-TPA) process in QDs. These findings underscore the potential of two distinct wavelength operations for optimizing the performance of quantum dot solar cells.