We report on the synthesis, characterization, and optoelectronic properties of the novel trimethylsulfonium lead triiodide perovskite, (CH3)3SPbI3. At room temperature, the air-stable compound adopts a hexagonal crystal structure with a 1D network of face-sharing [PbI6] octahedra along the c axis. UV-vis reflectance spectroscopy on a pressed pellet revealed a band gap of 3.1 eV, in agreement with first-principles calculations, which show a small separation between direct and indirect band gaps. Electrical resistivity measurements on single crystals indicated that the compound behaves as a semiconductor. According to multi-temperature single-crystal X-ray diffraction, synchrotron powder X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry, two fully reversible structural phase transitions occur at −5 and ca. −100 °C with reduction of the unit cell symmetry to monoclinic as temperature decreases. The role of the trimethylsulfonium cation regarding the chemical stability and optoelectronic properties of the new compound is discussed in comparison with APbI3 (A = Cs, methylammonium, and formamidinium cation), which are most commonly used in perovskite solar cells.
Bibliographical noteFunding Information:
Financial support from FP7 European Union (Marie Curie Initial Training Network DESTINY/316494) as well as from “Advanced Materials and Devices for Collection and Energy Management” project within GSRT’s KRIPIS action (MIS:452100), funded by Greece and the European Regional Development Fund of the European Union under NSRF 2007-2013 and the Regional Operational Program of Attica, is acknowledged. The work at Yonsei University was supported by the BK21+ programme, while the work at Imperial College London was supported by the Royal Society. Work at Northwestern University was supported by the Department of Energy, Office of Science, Basic Energy Sciences, under Grant SC0012541. We also acknowledge the provisional of beamtime at Diamond Light Source.
© 2017 American Chemical Society.