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Current transport studies of amorphous n/p junctions and its application in a‐Si:H/HIT‐type tandem cells
Author(s) -
Lee Youngseok,
Dao Vinh Ai,
Iftiquar S. M.,
Kim Sangho,
Yi Junsin
Publication year - 2016
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.2644
Subject(s) - tandem , materials science , optoelectronics , solar cell , heterojunction , amorphous silicon , quantum tunnelling , open circuit voltage , silicon , band gap , nanotechnology , crystalline silicon , voltage , electrical engineering , composite material , engineering
This paper presents an understanding of the fundamental carrier transport mechanism in hydrogenated amorphous silicon (a‐Si:H)‐based n/p junctions. These n/p junctions are, then, used as tunneling and recombination junctions (TRJ) in tandem solar cells, which were constructed by stacking the a‐Si:H‐based solar cell on the heterojunction with intrinsic thin layer (HIT) cell. First, the effect of activation energy ( E a ) and Urbach parameter ( E u ) of n‐type hydrogenated amorphous silicon (a‐Si:H(n)) on current transport in an a‐Si:H‐based n/p TRJ has been investigated. The photoluminescence spectra and temperature‐dependent current–voltage characteristics in dark condition indicates that the tunneling is the dominant carrier transport mechanism in our a‐Si:H‐based n/p‐type TRJ. The fabrication of a tandem cell structure consists of an a‐Si:H‐based top cell and an HIT‐type bottom cell with the a‐Si:H‐based n/p junction developed as a TRJ in between. The development of a‐Si:H‐based n/p junction as a TRJ leads to an improved a‐Si:H/HIT‐type tandem cell with a better open circuit voltage ( V oc ), fill factor ( FF ), and efficiency. The improvements in the cell performance was attributed to the wider band‐tail states in the a‐Si:H(n) layer that helps to an enhanced tunneling and recombination process in the TRJ. The best photovoltage parameters of the tandem cell were found to be V oc = 1430 mV, short circuit current density = 10.51 mA/cm 2 , FF = 0.65, and efficiency = 9.75%. Copyright © 2015 John Wiley & Sons, Ltd.