Thin silicon interference solar cells for targeted or broadband wavelength absorption enhancement.

Zeynep Durmaz,Rebecca Saive,Sebastian Husein

doi:10.1364/oe.413294

Abstract

We present the concept of interference solar cells reliant on spectrum filtering or splitting to enhance absorption in thin (<13 µm) silicon absorber layers, both for targeted wavelengths and broadband absorption. Absorption enhancement in the long wavelength regime is achieved by fine-tuning of device layer thicknesses to provide destructive interference between reflected and escaped waves. We suggest this concept is also suitable for broadband absorption enhancement when combined with spectrum splitting optics through gradual thickness changes laterally across the device. Using the example of silicon heterojunction solar cells, we have computationally demonstrated a short circuit current density enhancement of 19% (from 25.8 mA/cm2 to 30.7 mA/cm2) compared to a silicon heterojunction cell of the same absorber layer thickness.

Highlights

Silicon has been dominating the photovoltaic (PV) industry since its beginnings in the 1970s [1,2]
We present the computational design of a smooth front and rear surface silicon solar cell, which provides enhanced light trapping in the long wavelength regime through a wavelength-tuned optical cavity
We have introduced the concept of interference solar cells to enhance absorption in thin (

Summary

Introduction

Silicon has been dominating the photovoltaic (PV) industry since its beginnings in the 1970s [1,2]. It can be shown that for cells with a thickness significantly greater than the involved wavelength and coherence length, i.e., in the ray optical regime, optimum light trapping is achieved for perfect randomization of the light direction [15] In this case and for weakly absorbing conditions the path length enhancement amounts to 4n2, where n is the refractive index of the medium [15]. In the weakly absorbing regime, i.e., long wavelength absorption in silicon, strict interference conditions must be met for each involved wavelength separately In some applications such as for data transmission, only one specific wavelength is employed and the solar cells acting as photonic power converters have to be optimized for only one targeted wavelength [26,27,28]. Design parameters are highly tunable, allowing fabrication for multiple solar cell applications, including non-SHJ devices

Design of the interference silicon heterojunction solar cell

Optical performance of an interference solar cell

Findings

Discussion of the results

Summary and conclusions