Annealing effects on interdiffusion in layered FA-rich perovskite solar cells
D. O. Oyewole,
R. K. Koech,
R. Ichwani,
R. Ahmed,
J. Hinostroza Tamayo,
S. A. Adeniji,
J. Cromwell,
E. Colin Ulloa,
O. K. Oyewole,
B. Agyei-Tuffour,
L. V. Titova,
N. A. Burnham,
W. O. Soboyejo
Affiliations
D. O. Oyewole
Materials Science and Engineering Program, Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
R. K. Koech
Department of Materials Science and Engineering, African University of Science and Technology, Km 10 Airport Road, Galadimawa, P.M.B. 681, Garki-Abuja, Federal Capital Territory, Nigeria
R. Ichwani
Materials Science and Engineering Program, Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
R. Ahmed
Materials Science and Engineering Program, Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
J. Hinostroza Tamayo
Department of Physics, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
S. A. Adeniji
Department of Theoretical and Applied Physics, African University of Science and Technology, Km 10, Airport Road, Galadimawa, P.M.B. 681, Garki-Abuja, Federal Capital Territory, Nigeria
J. Cromwell
Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
E. Colin Ulloa
Department of Physics, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
O. K. Oyewole
Materials Science and Engineering Program, Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
B. Agyei-Tuffour
Department of Materials Science and Engineering, School of Engineering Sciences, University of Ghana, Legon-Accra, Ghana
L. V. Titova
Department of Physics, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
N. A. Burnham
Department of Physics, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
W. O. Soboyejo
Materials Science and Engineering Program, Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609, USA
Annealing is one of the processing methods that are used for the fabrication of defect-free, photoactive perovskite films with compact grains in highly efficient and stable perovskite solar cells (PSCs). Thus, the annealing temperature is a key parameter for the control of the interdiffusion (of constituent elements) in photoactive films. In this paper, we present the results of a systematic study of the effects of annealing on the interdiffusion of constituent elements in efficient formamidinium-based PSCs. We also explore the effects of annealing-induced interdiffusion on layer microstructures, local strains, and the optoelectronic properties of perovskite films. We observe a dramatic upward diffusion of tin (Sn) and titanium (Ti) from fluorine-doped tin oxide and titanium dioxide (TiO2) to the perovskite films. We also observe a downward diffusion of lead (Pb) and iodine (I) from the perovskite films to the mesoporous layer of the electron transporting layer (ETL), after annealing at temperatures between 100 and 150 °C. The diffused I substitutes for Ti in the ETL, which improves the optoelectronic properties of the films, for annealing temperatures between 100 and 130 °C. The annealing-induced interdiffusion that occurs at higher temperatures (between 140 and 150 °C) results in higher levels of interdiffusion, along with increased local strains that lead to the nucleation of pores and cracks. Finally, the implications of the results are discussed for the design of PSCs with improved photoconversion efficiencies and stability.
