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High‐efficiency silicon solar cells: Full factor limitations and non‐ideal diode behaviour due to voltage‐dependent rear surface recombination velocity
Author(s) -
Aberle Armin G.,
Robinson Stephen J.,
Wang Aihua,
Zhao Jianhua,
Wenham Stuart R.,
Green Martin A.
Publication year - 1993
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.4670010204
Subject(s) - equivalent series resistance , materials science , open circuit voltage , perl , common emitter , optoelectronics , electrical resistivity and conductivity , silicon , voltage , solar cell , electrical engineering , engineering , world wide web , computer science
Despite exceptionally high open‐circuit voltages, record high‐efficiency PERL (passivated emitter, rear locally diffused) silicon solar cells recently developed at the University of New South Wales demonstrate relatively low fill factors. This behaviour is shown to result from a surface recombination velocity at the rear Si‐SiO 2 interface that increases with reducing voltage across the cell, leading to non‐ideal I‐V curves with high ideality factors (>1.3) near the maximum power point. When corrected for series resistance losses, the Air Mass 1.5 (AM1.5) fill factor of actual PERL cells is found to be limited to values below 82.9%, as opposed to the ideal theoretical limit of 85‐86% for silicon cells operating in low injection conditions. Relatively large series resistance losses (R s > 0.35 ω cm 2 ) further reduce this value to the experimentally observed fill factors below 81.4%. Analysis of measured illuminated and dark I‐V characteristics of PERL cells reveals that the AM1.5 efficiency is mainly limited by recombination losses at the rear oxidized surface. Optimum PERL cell resistivity is about 2 ω cm. Owing to increased rear surface recombination velocity, lower resistivity material shows no advantage in open‐circuit voltage and suffers from short‐circuit current losses, while a strong reduction in the surface recombination velocity above the maximum power point results in smaller fill factors. High‐resistivity cells do show an improved short‐cuircuit current but suffer from voltage and fill factor losses.