Open AccessConversion efficiency limits and bandgap designs for multi-junction solar cells with internal radiative efficiencies below unity
Author(s) -
Lin Zhu,
Takayasu Mochizuki,
Masahiro Yoshita,
Shaoqiang Chen,
Changsu Kim,
Hidefumi Akiyama,
Yoshihiko Kanemitsu
Publication year - 2016
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.24.00a740
Subject(s) - energy conversion efficiency , band gap , radiative transfer , optics , solar cell efficiency , stack (abstract data type) , materials science , limit (mathematics) , optoelectronics , physics , solar cell , mathematical analysis , mathematics , computer science , programming language
We calculated the conversion-efficiency limit ηsc and the optimized subcell bandgap energies of 1 to 5 junction solar cells without and with intermediate reflectors under 1-sun AM1.5G and 1000-sun AM1.5D irradiations, particularly including the impact of internal radiative efficiency (ηint) below unity for realistic subcell materials on the basis of an extended detailed-balance theory. We found that the conversion-efficiency limit ηsc significantly drops when the geometric mean ηint* of all subcell ηint in the stack reduces from 1 to 0.1, and that ηsc degrades linearly to logηint* for ηint* below 0.1. For ηint*<0.1 differences in ηsc due to additional intermediate reflectors became very small if all subcells are optically thick for sun light. We obtained characteristic optimized bandgap energies, which reflect both ηint* decrease and AM1.5 spectral gaps. These results provide realistic efficiency targets and design principles.