I-009

Rokas Kondrotas

rokas.kondrotas@ftmc.lt

Arnas Naujokaitis, Martynas Talaikis, Vidas Pakstas, Juri Krustok, Trong Tien, Sussane Siebentritt

Center for Physical Science and Technology (FTMC), Lithuania

Defect passivation in antimony selenide for improved photovoltaic performance

Antimony selenide (Sb2Se3) is an emerging photovoltaic material spurring significant interest in the field of earth abundant and low-toxicity thin films for energy conversion application such as solar cells and photocathodes [1,2]. Dedicated research on Sb2Se3 solar cells started eleven years ago resulting in a steady increase in power conversion efficiency (PCE) of solar cells to over 10%. However for the past 4-5 years the PCE has stagnated questioning whether fundamental or technological limitations are in play for further development. At present, high open-circuit voltage (VOC) deficit has been recognized as the main performance limiting factor in solar cells and its improvement is paramount for achieving high efficiency Sb2Se3 photovoltaic devices in the future. VOC deficit can be caused by non-optimal band alignment in the junction, but more often is related to significant nonradiative recombination via deep defects at the interfaces or in the bulk of the absorber. The defect chemistry of Sb2Se3 is complex due to low crystal symmetry and multiple inequivalent positions of the same atoms in the crystal lattice. This gives rise to a plethora of point defects among which selenium vacancies have been predicted to be the most detrimental, and their elimination is key to increase device performance [4]. In this talk, the issue of large VOC deficit is discussed on both levels - fundamental and technological. Employing photoluminescence spectroscopy as the primary tool, we investigate radiative properties of Sb2Se3 crystals and thin films. By studying photoluminescence properties of single crystals we unravel the main recombination mechanism showing no fundamental limitations exist for Sb2Se3 to reach near theoretical VOC values. By analysing emission intensity from Sb2Se3 thin films, we devised optimal reactive treatment conditions allowing to reach PCE beyond state-of-the-art Sb2Se3 based devices.    

Reference:

1. Chen C, Li K, Tang J. Ten years of Sb2Se3 thin film solar cells. Solar RRL. 2022 Jul;6(7):2200094.

2. Yang W, Kim JH, Hutter OS, Phillips LJ, Tan J, Park J, Lee H, Major JD, Lee JS, Moon J. Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting. Nature communications. 2020 Feb 13;11(1):861.

3. Wang X, Kavanagh SR, Scanlon DO, Walsh A. Upper efficiency limit of Sb2Se3 solar cells. Joule. 2024 Jul 17;8(7):2105-22.