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Rapid Thermal Treatment of Reactive Sputtering Grown Nanocrystalline Co 3 O 4 for Enhanced All‐Oxide Photovoltaics
Author(s) -
Patel Malkeshkumar,
Park SungHo,
Kim Joondong
Publication year - 2018
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201800216
Subject(s) - materials science , nanocrystalline material , photovoltaics , sputtering , oxide , spinel , optoelectronics , band gap , thermal treatment , photovoltaic system , nanotechnology , chemical engineering , thin film , metallurgy , composite material , ecology , engineering , biology
All‐oxide photovoltaics are important eco‐energy systems because the metal oxide materials are non‐toxic, easy to fabricate, earth abundant, and chemically stable. The authors report on spinel Co 3 O 4 ‐based all‐oxide photovoltaics and their performance enhancement via post‐rapid thermal processing (RTP). Preferentially oriented nanocrystalline Co 3 O 4 film with a dual band gap ( E g ) is grown by reactive sputtering of Co, which exhibits degenerate semiconductor properties due to native oxygen vacancies. The authors find that RTP treatment effectively overcomes the native defects in the Co 3 O 4 , and enables the free carrier concentration to be tuned over a wide range (10 17 –10 20 cm −3 ). It also efficiently enhances hole mobility by 50 times, without affecting the E g values. A semitransparent Co 3 O 4 device with an optimally thick TiO 2 layer exhibits enhancements in V OC , from 0.42 to 0.7 V, J SC from 0.88 to 3.47 mA cm −2 , and efficiency from 0.1 to 0.6% when treated by RTP at 550 °C. Following RTP, a pristine device exhibits enhanced photovoltaic performance due to synergetic optical and electrical properties. These results confirm the benefits of post‐thermal treatment for enhancing all‐oxide photovoltaic performance, and tuning the optoelectronic properties of metal oxides.