High-Efficiency and Ultra-Stable Cesium–Bismuth-Based Lead-free Perovskite Solar Cells without Modification

Abstract

Perovskite solar cells (PSCs) have become a new photovoltaic technology with great commercial potential because of their excellent photovoltaic performance. However, the toxicity and poor environmental stability of Pb in Pbbased perovskites limit its large-scale application. Exploring alternatives to Pb is an available approach to develop environmentally friendly PSCs. As an adjacent element of Pb, Bi shows many similar physical and chemical properties; therefore, it is commonly applied for B site substitution in Pb-based PSCs. CsBiSCl 2 , a new Pbfree perovskite system, was synthesized for the first time as a light absorber. By preparing DMABiS 2 as an intermediate, Cs−Bi-based CsBiSCl 2 perovskite films with a band gap over 2.012 eV were prepared by introducing CsCl, and the optimal annealing temperature, time, and stoichiometric ratio of the film were explored in this work. The conventional structure of CsBiSCl 2 PSCs achieved a power conversion efficiency (PCE) of 10.38%, and the efficiency declined by only 3% after aging in air for 150 days, showing excellent stability, which is one of the most stable devices in inorganic PSCs. This work opens up a new road for the future development of environmentally friendly and commercially stable lead-free PSCs.

Prospective Chalcohalide Perovskites: Pursuing (and Failing) the Synthesis of CsBiSCl2 Nanocrystals

“…Thin films of CsBiSCl 2 were used as solar absorber in photovoltaic devices yielding a power conversion efficiency above 10% and long-term stability at ambient conditions, suggesting a highly promising alternative to Pb halide perovskite photovoltaics . The preparation of CsBiSCl 2 chalcohalide perovskite was reported as the result of depositing and annealing a mixture of an ammonium Bi sulfide compound with CsCl in polar solvents . We find that a straightforward identification of the reaction products remains, in our opinion, elusive, in analogy to previous reports on the synthesis of other AM­(E,X) 3 compounds. − …”

“…In addition, an experimental study recently reported the first synthesis of CsBiSCl 2 . Thin films of CsBiSCl 2 were used as solar absorber in photovoltaic devices yielding a power conversion efficiency above 10% and long-term stability at ambient conditions, suggesting a highly promising alternative to Pb halide perovskite photovoltaics . The preparation of CsBiSCl 2 chalcohalide perovskite was reported as the result of depositing and annealing a mixture of an ammonium Bi sulfide compound with CsCl in polar solvents .…”

“…However, the formation of secondary phases, such as binary halides (AX and MX 3 ) and chalcogenides (M 2 E 3 ), was predicted as thermodynamically favored compared to the formation of the quaternary AM­(E,X) 3 phases; this prediction was experimentally corroborated by unsuccessful attempts of preparing some AM­(E,X) 3 compounds via solid state synthesis . Nevertheless, the synthesis via solid state chemistry and thin film deposition of compounds identified as heavy pnictogen chalcohalide perovskites was reported; − however, the actual formation of such chalcohalide perovskite was disputed, and the outcome of these synthetic approaches is controversial at least . These experimental studies and their contrasting interpretation, together with the limited research in this direction, indicate that the synthesis of AM­(E,X) 3 compounds under thermodynamic control may prevalently, if not exclusively, yield spurious phases.…”

“…In addition, an experimental study recently reported the first synthesis of CsBiSCl 2 . Thin films of CsBiSCl 2 were used as solar absorber in photovoltaic devices yielding a power conversion efficiency above 10% and long-term stability at ambient conditions, suggesting a highly promising alternative to Pb halide perovskite photovoltaics .…”