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Resolving Hysteresis in Perovskite Solar Cells with Rapid Flame‐Processed Cobalt‐Doped TiO 2
Author(s) -
Kim Jung Kyu,
Chai Sung Uk,
Ji Yongfei,
LevyWendt Ben,
Kim Suk Hyun,
Yi Yeonjin,
Heinz Tony F.,
Nørskov Jens K.,
Park Jong Hyeok,
Zheng Xiaolin
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201801717
Subject(s) - materials science , dopant , doping , photocurrent , perovskite (structure) , hysteresis , band gap , energy conversion efficiency , chemical engineering , analytical chemistry (journal) , nanotechnology , optoelectronics , condensed matter physics , organic chemistry , engineering , chemistry , physics
To further increase the open‐circuit voltage ( V oc ) of perovskite solar cells (PSCs), many efforts have been devoted to doping the TiO 2 electron transport/selective layers by using metal dopants with higher electronegativity than Ti. However, those dopants can introduce undesired charge traps that hinder charge transport through TiO 2 , so the improvement in the V oc is often accompanied by an undesired photocurrent density–voltage ( J–V ) hysteresis problem. Herein, it is demonstrated that the use of a rapid flame doping process (40 s) to introduce cobalt dopant into TiO 2 not only solves the J–V hysteresis problem but also increases the V oc and power conversion efficiency of both mesoscopic and planar PSCs. The reasons for the simultaneous improvements are two fold. First, the flame‐doped Co‐TiO 2 film forms Co‐O v (cobalt dopant‐oxygen vacancy) pairs and hence reduces the number density of Ti 3+ trap states. Second, Co doping upshifts the band structure of TiO 2 , facilitating efficient charge extraction. As a result, for planar PSCs, the flame doping of Co increases the efficiency from 17.1% to 18.0% while reducing the hysteresis from 16.0% to 1.7%. Similarly, for mesoscopic PSCs, the flame doping of Co increases the efficiency from 18.5% to 20.0% while reducing the hysteresis from 7.0% to 0.1%.