Band offsets of n-type electron-selective contacts on cuprous oxide (Cu{sub 2}O) for photovoltaics

Journal Article · Mon Dec 29 00:00:00 EST 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4905180· OSTI ID:22395627

Lee, Yun Seog; Buonassisi, Tonio ^[1]; Young, Matthew; Dameron, Arrelaine; Teeter, Glenn ^[2]; Park, Helen Hejin; Chua, Danny; Gordon, Roy G. ^[3]

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1. Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
2. National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)
3. Harvard University, Cambridge, Massachusetts 02139 (United States)

The development of cuprous oxide (Cu{sub 2}O) photovoltaics (PVs) is limited by low device open-circuit voltages. A strong contributing factor to this underperformance is the conduction-band offset between Cu{sub 2}O and its n-type heterojunction partner or electron-selective contact. In the present work, a broad range of possible n-type materials is surveyed, including ZnO, ZnS, Zn(O,S), (Mg,Zn)O, TiO{sub 2}, CdS, and Ga{sub 2}O{sub 3}. Band offsets are determined through X-ray photoelectron spectroscopy and optical bandgap measurements. A majority of these materials is identified as having a negative conduction-band offset with respect to Cu{sub 2}O; the detrimental impact of this on open-circuit voltage (V{sub OC}) is evaluated through 1-D device simulation. These results suggest that doping density of the n-type material is important as well, and that a poorly optimized heterojunction can easily mask changes in bulk minority carrier lifetime. Promising heterojunction candidates identified here include Zn(O,S) with [S]/[Zn] ratios >70%, and Ga{sub 2}O{sub 3}, which both demonstrate slightly positive conduction-band offsets and high V{sub OC} potential. This experimental protocol and modeling may be generalized to evaluate the efficiency potential of candidate heterojunction partners for other PV absorbers, and the materials identified herein may be promising for other absorbers with low electron affinities.

• OSTI ID: 22395627
• Journal Information: Applied Physics Letters, Vol. 105, Issue 26; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AFFINITY
CADMIUM SULFIDES
CARRIER LIFETIME
COPPER OXIDES
ELECTRIC POTENTIAL
ELECTRONS
GALLIUM OXIDES
HETEROJUNCTIONS
N-TYPE CONDUCTORS
PHOTOVOLTAIC EFFECT
POTENTIALS
TITANIUM OXIDES
X-RAY PHOTOELECTRON SPECTROSCOPY
ZINC OXIDES
ZINC SULFIDES