Preparation of Single-Phase Films of CH3NH3Pb(I1-xBrx)3 with Sharp Optical Band Edges.
Organometallic lead-halide perovskite-based solar cells now approach 18% efficiency. Introducing a mixture of bromide and iodide in the halide composition allows tuning of the optical bandgap. We prepare mixed bromide-iodide lead perovskite films CH3NH3Pb(I1-xBrx)3 (0 ≤ x ≤ 1) by spin-coating from solution and obtain films with monotonically varying bandgaps across the full composition range. Photothermal deflection spectroscopy, photoluminescence, and X-ray diffraction show that following suitable fabrication protocols these mixed lead-halide perovskite films form a single phase. The optical absorption edge of the pure triiodide and tribromide perovskites is sharp with Urbach energies of 15 and 23 meV, respectively, and reaches a maximum of 90 meV for CH3NH3PbI1.2Br1.8. We demonstrate a bromide-iodide lead perovskite film (CH3NH3PbI1.2Br1.8) with an optical bandgap of 1.94 eV, which is optimal for tandem cells of these materials with crystalline silicon devices.
†Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Aditya
A
Sadhanala
†Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Felix
F
Deschler
†Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Tudor H
TH
Thomas
†Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Siân E
SE
Dutton
†Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Karl C
KC
Goedel
‡Ludwig-Maximilians-Universität München, Butenandtstraße 11, 81377 München, Germany.
Fabian C
FC
Hanusch
†Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
May L
ML
Lai
†Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Ullrich
U
Steiner
‡Ludwig-Maximilians-Universität München, Butenandtstraße 11, 81377 München, Germany.
Thomas
T
Bein
‡Ludwig-Maximilians-Universität München, Butenandtstraße 11, 81377 München, Germany.
Pablo
P
Docampo
§Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.
David
D
Cahen
†Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Richard H
RH
Friend
PDS; Urbach energy; iodide-bromide perovskite; organometallic lead halide perovskite