Designing limiting-efficiency BaSi2 solar cells by device simulation and computational material screening

• Published in: Solar energy Vol. 245; pp. 136 - 145
• Main Author: Hara, Kosuke O.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2022
• Subjects: Barium silicide; Charge transport layer; Density functional theory; Device simulation; Photovoltaics; Charge transport layer; Density functional theory; Barium silicide; Device simulation; Photovoltaics
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2022.08.044

A double heterojunction solar cell consisting of a solar absorber and electron/hole transport layers (ETL/HTL) is ideally efficient and can contribute to the exploitation of solar energy. BaSi2 is an attractive solar absorber material possessing a band gap of 1.3 eV and high absorption coefficients. However, finding proper ETL/HTL materials remains challenging. Here, limiting efficiency calculation, device simulation, and computational material screening are combined to design BaSi2 solar cells of near-limiting efficiency (> 28%). The limiting efficiency is calculated considering radiative and trap-assisted Auger recombinations, which shows that the Lambertian limit efficiency (32%) exceeds that of Si cells. Device simulations of double heterojunction BaSi2 cells were performed with different values of band gap, ionization potential, and electron affinity, which yields criteria for band-edge energy levels of the ETL and HTL. Candidate materials for the ETL and HTL are identified from the Materials Project database by three-step screening. The first step screens the materials for band gap, interface reactivity, lattice matching, etc. The second step is a literature survey to exclude air-sensitive or unstable materials under ambient conditions. In the third step, band-edge levels are calculated using density functional theory, and eight ETL and seven HTL candidate materials are identified. This device design method is applicable to any solar absorber material and promotes accelerated solar cell development. [Display omitted] •Procedure to find proper materials for charge transport layers of solar cells.•Materials are screened by band alignment, chemical reactivity, and lattice matching.•Device simulation yields the criteria for band edge levels.•Computational database screening finds tentative candidate materials.•Band-edge level calculations by DFT identify final candidates.