Publication

Science, 368, 6487, 155-160

Daehan Kim, Joon Jung, Jae Park, Bryon W. Larson, Sean P. Dunfield, Chuanxiao Xiao, Jekyung Kim, Jinhui Tong, Passarut Boonmongkolras, Su Geun Ji, Fei Zhang, Seong Ryul Pae, Minkyu Kim, Seok Beom Kang, Vinayak Dravid, Joseph J. Berry, Jin Young Kim, Kai Zhu, Dong Hoe Kim, Byungha Shin

Maximizing the power conversion efficiency (PCE) of perovskite/silicon tandem solar cells that can exceed the Shockley-Queisser single-cell limit requires a high-performing, stable perovskite top cell with a wide bandgap. We developed a stable perovskite solar cell with a bandgap of ~1.7 electron volts that retained more than 80% of its initial PCE of 20.7% after 1000 hours of continuous illumination. Anion engineering of phenethylammonium-based two-dimensional (2D) additives was critical for controlling the structural and electrical properties of the 2D passivation layers based on a lead iodide framework. The high PCE of 26.7% of a monolithic two-terminal wide-bandgap perovskite/silicon tandem solar cell was made possible by the ideal combination of spectral responses of the top and bottom cells.

Nature, 575, 151-155 (2019)

Oki Gunawan, Seong Ryul Pae, Douglas M. Bishop, Yudistira Virgus, Jun Hong Noh, Nam Joong Jeon, Yun Seog Lee, Xiaoyan Shao, Teodor Todorov, David B. Mitzi & Byungha Shin

The fundamental parameters of majority and minority charge carriers—including their type, density and mobility—govern the performance of semiconductor devices yet can be difficult to measure. Although the Hall measurement technique is currently the standard for extracting the properties of majority carriers, those of minority carriers have typically only been accessible through the application of separate techniques. Here we demonstrate an extension to the classic Hall measurement—a carrier-resolved photo-Hall technique—that enables us to simultaneously obtain the mobility and concentration of both majority and minority carriers, as well as the recombination lifetime, diffusion length and recombination coefficient. This is enabled by advances in a.c.-field Hall measurement using a rotating parallel dipole line system and an equation, Δμ_H = d(σ²H)/dσ, which relates the hole–electron Hall mobility difference (Δμ_H), the conductivity (σ) and the Hall coefficient (H). We apply this technique to various solar absorbers—including high-performance lead-iodide-based perovskites—and demonstrate simultaneous access to majority and minority carrier parameters and map the results against varying light intensities. This information, which is buried within the photo-Hall measurement, had remained inaccessible since the original discovery of the Hall effect in 1879. The simultaneous measurement of majority and minority carriers should have broad applications, including in photovoltaics and other optoelectronic devices.