Copper indium selenide water splitting photoanodes with artificially designed heterophasic blended structure and their high photoelectrochemical performances

• Published in: Nano energy 2018-04, Vol.46, p.1-10
• Main Authors: Kim, Joo Sung, Baek, Seung Ki, Kim, Young Been, Do, Hyun Woo, Kwon, Yong Hun, Cho, Sung Woon, Yun, Young Dae, Yoon, Jae Hong, Lee, Han-Bo-Ram, Kim, Sang-Woo, Cho, Hyung Koun
• Format: Article
• Language: English
• Subjects: Built-in potential; Charge separation; Heterophasic blended structure; Photoanode; Photoelectrochemical cell
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2018.01.023

Conventional p-CuInSe2 absorbers for solar cells have been homogenously synthesized using multi-step process despite a narrow crystal phase region in the phase diagram and the existence of various secondary phases. In contrast, here we propose artificially-designed heterophasic blended copper indium selenide compounds for water splitting photoanodes using a simple one-step annealing synthetic process where the electrodeposited metal precursors were directly annealed with Se vapor injection and without additional intermediate steps. The resultant product is revealed to possess a novel “phase-blended structure” comprising two phases of p-type CuInSe2 and n-type CuIn3Se5 crystals. The CuInSe2 nanoparticles with a higher Cu fraction are three-dimensionally (3D) embedded in the n-type CuIn3Se5 matrix, which has been verified by various analysis methods such as X-ray diffraction, transmission electron microscopy, and capacitance-voltage curve. The average diameter of the CuInSe2 nanoparticles is 66.8nm and the interval between the nanoparticles in the CuIn3Se5 matrix is 67.6nm. Consequently, the phase-blended structure photoabsorber exhibits a remarkably enhanced anodic photocurrent of 12.7mA/cm2 at 1.23V versus the reversible hydrogen electrode. The considerably enhanced photocurrent gain of the phase-blended structure photoanode is attributed to the excellent charge separation facilitated by the built-in potential generated from the 3D p-n junction. We report an inorganic heterophasic blended structure with remarkably enhanced photocurrent performance via built-in potential between p-type CuInSe2 nanoparticles and n-type CuIn3Se5 matrix. [Display omitted] •Inorganic heterophasic blended structure was synthesized via one-step annealing process of electrodeposited Cu/In bilayers.•We designed inorganic heterophasic blended structure consisting of p-type CuInSe2 nanoparticles and n-type CuIn3Se5 matrix.•The nanoscale CuInSe2 nanoparticles with a higher Cu fraction were three-dimensionally embedded in n-type CuIn3Se5 matrix.•Phase-blended structure resulted in sufficient depletion and efficiently separated photo-generated electron-hole pairs.•Phase-blended structure CIS showed remarkably enhanced photocurrent and good stability with an ultra-thin Al2O3 layer.