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Title: Back-contacted bottom cells with three terminals: Maximizing power extraction from current-mismatched tandem cells

Abstract

Multi-junction cells can significantly improve the energy yield of photovoltaic systems over a single-junction cell. The internal interconnection scheme of the subcells is an important aspect in determining the resulting levelized cost of electricity. For a dual-junction cell, two approaches are commonly discussed: series-connected tandem cells with two terminals or independently working subcells in a four-terminal (4T) tandem device. In this paper, we explore the working principle and the operation modes of a third, rarely discussed option: a three-terminal (3T) tandem cell using a back-contacted bottom cell with 3Ts. We use current-voltage measurements of illuminated 3T interdigitated back contact cells and confirm that the front and rear base contacts are at similar quasi-Fermi level positions, which enables the bottom cell to either efficiently collect surplus carriers, in the case of a current-limiting or carrier injecting top cell, or inject majority carriers, in the case of a current-limiting bottom cell. As a result, no current matching is needed. The power output of an idealized 3T bottom cell without resistive effects is independent of the current density applied from the top cell. These characteristics of the 3T bottom cells enable a 3T tandem to operate as efficiently as a 4T tandem, whilemore » being compatible with monolithic design and not requiring intermediate grids. We propose a simple equivalent circuit model including additional resistive effects, which describes a real 3T bottom cell and achieves excellent agreement to the experiment. We deduce design guidelines for a 3T bottom cell in different operation regimes.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [2];  [3];  [4];  [1];  [2];  [2];  [1]
  1. Inst. for Solar Energy Research Hamelin (ISFH), Emmerthal (Germany); Leibniz Univ. Hannover, Hannover (Germany)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States); Inst. for Solar Energy Research Hamelin (ISFH), Emmerthal (Germany)
  4. Institute for Solar Energy Research Hamelin (ISFH) Emmerthal Germany
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1503161
Alternate Identifier(s):
OSTI ID: 1493641
Report Number(s):
NREL/JA-5900-71667
Journal ID: ISSN 1062-7995
Grant/Contract Number:  
AC36-08GO28308; DE‐AC36‐08GO28308
Resource Type:
Accepted Manuscript
Journal Name:
Progress in Photovoltaics
Additional Journal Information:
Journal Volume: 27; Journal Issue: 5; Journal ID: ISSN 1062-7995
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; 3T; bipolar junction transistor tandem bottom cell; current-mismatch; interdigitated back contact cell (IBC); tandem solar cell; three terminal

Citation Formats

Rienäcker, Michael, Warren, Emily L., Schnabel, Manuel, Schulte‐Huxel, Henning, Niepelt, Raphael, Brendel, Rolf, Stradins, Pauls, Tamboli, Adele C., and Peibst, Robby. Back-contacted bottom cells with three terminals: Maximizing power extraction from current-mismatched tandem cells. United States: N. p., 2019. Web. doi:10.1002/pip.3107.
Rienäcker, Michael, Warren, Emily L., Schnabel, Manuel, Schulte‐Huxel, Henning, Niepelt, Raphael, Brendel, Rolf, Stradins, Pauls, Tamboli, Adele C., & Peibst, Robby. Back-contacted bottom cells with three terminals: Maximizing power extraction from current-mismatched tandem cells. United States. doi:10.1002/pip.3107.
Rienäcker, Michael, Warren, Emily L., Schnabel, Manuel, Schulte‐Huxel, Henning, Niepelt, Raphael, Brendel, Rolf, Stradins, Pauls, Tamboli, Adele C., and Peibst, Robby. Wed . "Back-contacted bottom cells with three terminals: Maximizing power extraction from current-mismatched tandem cells". United States. doi:10.1002/pip.3107.
@article{osti_1503161,
title = {Back-contacted bottom cells with three terminals: Maximizing power extraction from current-mismatched tandem cells},
author = {Rienäcker, Michael and Warren, Emily L. and Schnabel, Manuel and Schulte‐Huxel, Henning and Niepelt, Raphael and Brendel, Rolf and Stradins, Pauls and Tamboli, Adele C. and Peibst, Robby},
abstractNote = {Multi-junction cells can significantly improve the energy yield of photovoltaic systems over a single-junction cell. The internal interconnection scheme of the subcells is an important aspect in determining the resulting levelized cost of electricity. For a dual-junction cell, two approaches are commonly discussed: series-connected tandem cells with two terminals or independently working subcells in a four-terminal (4T) tandem device. In this paper, we explore the working principle and the operation modes of a third, rarely discussed option: a three-terminal (3T) tandem cell using a back-contacted bottom cell with 3Ts. We use current-voltage measurements of illuminated 3T interdigitated back contact cells and confirm that the front and rear base contacts are at similar quasi-Fermi level positions, which enables the bottom cell to either efficiently collect surplus carriers, in the case of a current-limiting or carrier injecting top cell, or inject majority carriers, in the case of a current-limiting bottom cell. As a result, no current matching is needed. The power output of an idealized 3T bottom cell without resistive effects is independent of the current density applied from the top cell. These characteristics of the 3T bottom cells enable a 3T tandem to operate as efficiently as a 4T tandem, while being compatible with monolithic design and not requiring intermediate grids. We propose a simple equivalent circuit model including additional resistive effects, which describes a real 3T bottom cell and achieves excellent agreement to the experiment. We deduce design guidelines for a 3T bottom cell in different operation regimes.},
doi = {10.1002/pip.3107},
journal = {Progress in Photovoltaics},
number = 5,
volume = 27,
place = {United States},
year = {2019},
month = {2}
}

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