Antimony Trichalcogenide Materials for Short-Wavelength Infrared Photovoltaic (SWIR-PV) Devices

Coupling a short wavelength infrared (SWIR) PV device with a bandgap of 0.6-0.7 eV to tandem PV technologies can improve overall power conversion efficiency (PCE) by 5-11%. Alternatively, a SWIR device can be used in a thermophotovoltaic system and (ideally) furnish a PCE > 50%. However, there is a limited variety of low-cost light absorbers for the SWIR region. Antimony trichalcogenides, such as Sb₂Se₃, exhibit a large absorption coefficient (~10⁵) and a long diffusion length (~1.7 µm). Made of earth-abundant materials and by rapid and low-cost deposition methods, Sb₂Se₃solar cells with PCE > 10% were recently reported. Three other qualities make Antimony trichalcogenides promising SWIR-PV materials: i) Due to the unique quasi-one-dimensional crystal structure, certain grain boundaries in Sb₂Se₃thin films are expected to be electronically benign. ii) due to the antibonding states at the top of the valence band, Sb₂Se₃is expected to be (point) defect tolerant. iii) The bandgap of Sb₂Se₃ can be tuned to the SWIR region by alloying with Bi. Here we report a method for making thin films and solar cells of Bi-alloyed PV. By using closed space sublimation, we successfully incorporated Bi in Sb₂Se₃up to 40%At. without forming secondary phases. The absorption edge extended from 1050 to 1370 nm. Proof-of-concept solar cells will also be presented.