Doping-free Janus homojunction solar cell with efficiency exceeding 23%

TL;DR

This paper introduces a doping-free Janus homojunction solar cell using two-dimensional Janus semiconductors, achieving over 23% efficiency by leveraging intrinsic dipoles and electric fields to improve carrier separation and light absorption.

Contribution

It presents a novel doping-free homojunction solar cell design based on Janus semiconductors, demonstrating high efficiency without traditional doping methods.

Findings

Theoretical PCE of 23.22% for TiSSe Janus homojunction.

Intrinsic electric fields enhance carrier separation and transport.

Janus structure promotes type-II band alignment for better exciton dissociation.

Abstract

Photovoltaic solar cell is one of the main renewable energy sources, and its power conversion efficiency (PCE) is improved by employing doping or heterojunction to reduce the photogenerated carrier recombination. Here, we propose a doping-free homojunction solar cell utilizing two-dimensional Janus semiconductors to achieve high PCE. Thanks to the intrinsic dipole of Janus structure, doping-free Janus homojunction has naturally not only a type-II band alignment to promote the photoexciton dissociation, but also a smaller effective bandgap to enhance light absorption. More importantly, the intrinsic electric field across the Janus structure will drive photoinduced electron and hole transfer from the interface to the opposite transport layers respectively, significantly enhancing the efficiency of carrier separation and transport. We illustrate the concept in titanium-based Janus monolayer homojunction, where the theoretically observed PCE reaches 23.22% of TiSSe homojunction. Our work opens a novel avenue to design low-cost, high-efficiency solar cells.