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Enhanced Efficiency in Plastic Solar Cells via Energy Matched Solution Processed NiO x Interlayers
Author(s) -
Steirer K. Xerxes,
Ndione Paul F.,
Widjonarko N. Edwin,
Lloyd Matthew T.,
Meyer Jens,
Ratcliff Erin L.,
Kahn Antoine,
Armstrong Neal R.,
Curtis Calvin J.,
Ginley David S.,
Berry Joseph J.,
Olson Dana C.
Publication year - 2011
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.201100234
Subject(s) - materials science , non blocking i/o , work function , pedot:pss , organic solar cell , x ray photoelectron spectroscopy , indium tin oxide , energy conversion efficiency , solar cell , ultraviolet photoelectron spectroscopy , polymer solar cell , chemical engineering , analytical chemistry (journal) , optoelectronics , layer (electronics) , nanotechnology , composite material , organic chemistry , chemistry , catalysis , polymer , engineering
We show enhanced efficiency and stability of a high performance organic solar cell (OPV) when the work‐function of the hole collecting indium‐tin oxide (ITO) contact, modified with a solution‐processed nickel oxide (NiO x ) hole‐transport layer (HTL), is matched to the ionization potential of the donor material in a bulk‐heterojunction solar cell. Addition of the NiO x HTL to the hole collecting contact results in a power conversion efficiency ( PCE ) of 6.7%, which is a 17.3% net increase in performance over the 5.7% PCE achieved with a poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL on ITO. The impact of these NiO x films is evaluated through optical and electronic measurements as well as device modeling. The valence and conduction band energies for the NiO x HTL are characterized in detail through photoelectron spectroscopy studies while spectroscopic ellipsometry is used to characterize the optical properties. Oxygen plasma treatment of the NiO x HTL is shown to provide superior contact properties by increasing the ITO/NiO x contact work‐function by 500 meV. Enhancement of device performance is attributed to reduction of the band edge energy offset at the ITO/NiO x interface with the poly(N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothidiazole) (PCDTBT):[6,6]‐phenyl‐C61 butyric acid methyl ester PCBM and [6,6]‐phenyl‐C71 butyric acid methyl ester (PC 70 BM) active layer. A high work‐function hole collecting contact is therefore the appropriate choice for high ionization potential donor materials in order to maximize OPV performance.