Surface engineering of photoelectrodes is considered critical for achieving efficient photoelectrochemical (PEC) cells, and various p-type materials have been investigated for use as photoelectrodes. Among these, the p-type semiconductor/n-type CdS heterojunction is the most successful photocathode structure because of its enhanced onset potential and photocurrent. However, it is determined that the main contributor to the enhanced activity is the Cd-doped layer and not the CdS layer. In this study, a Cd-doped n+p-buried homojunction of a CuInS2 photocathode is first demonstrated without a CdS layer. The homojunction exhibited a more active and stable PEC performance than the CdS/CuInS2 heterojunction. Moreover, it is confirmed that Cd doping is effective for other p-type materials. These results strongly suggest that the effects of Cd doping on photocathodes should be carefully investigated when designing CdS/p-semiconductor heterojunction photoelectrodes. They also indicate that the Cd-doped layer has great potential to replace the CdS layer in future photoelectrode designs.
S.Y.C. and M.J. contributed equally to this work. This study was supported by the C1 Gas Refinery Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT, and Future Planning (grant no. 2015M3D3A1A01064899); the Basic Science Research Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education (grant no. RS-2023-00249042); the Learning & Academic Research Institution for Master & PhD students and Postdocs (LAMP) Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education (grant no. RS-2023-00285390); the Program of Future Hydrogen Original Technology Development (grant no. NRF-2021M3I3A1082879) through the National Research Foundation of Korea (NRF), funded by the South Korean government (Ministry of Science and ICT); the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant, funded by the South Korean government (MOTIE) (grant no. 20213030030260); the KIST Institutional Program (grant nos. 2E33281 and KIST-2E31831).This study was supported by the C1 Gas Refinery Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT, and Future Planning (grant no. 2015M3D3A1A01064899); the Basic Science Research Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education (grant no. RS\u20102023\u201000249042); the Learning & Academic Research Institution for Master & PhD students and Postdocs (LAMP) Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education (grant no. RS\u20102023\u201000285390); the Program of Future Hydrogen Original Technology Development (grant no. NRF\u20102021M3I3A1082879) through the National Research Foundation of Korea (NRF), funded by the South Korean government (Ministry of Science and ICT); the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant, funded by the South Korean government (MOTIE) (grant no. 20213030030260); the KIST Institutional Program (grant nos. 2E33281 and KIST\u20102E31831).
