TY - JOUR
T1 - Charge Carrier Dynamics in Co-evaporated MAPbI3with a Gradient in Composition
AU - Zhao, Jiashang
AU - Li, Jia
AU - Liu, Xiaohui
AU - Bannenberg, Lars J.
AU - Bruno, Annalisa
AU - Savenije, Tom J.
PY - 2022
Y1 - 2022
N2 - Co-evaporation of metal halide perovskites by thermal evaporation is an attractive method since it does not require harmful solvents and enables precise control of the film thickness. Furthermore, the ability to manipulate the Fermi level allows the formation of a graded homojunction, providing interesting opportunities to improve the charge carrier collection efficiency. However, little is known about how these properties affect the charge carrier dynamics. In this work, the structural and optoelectronic properties of co-evaporated MAPbI3 films varying in thickness (100, 400, and 750 nm) with a gradient in composition are analyzed. The X-ray diffraction patterns show that excess PbI2 is only present in the thick layers. From X-ray photoelectron spectroscopy depth analysis, the I/Pb atomic ratio indicates methylammonium iodide deficiencies that become more prominent with thicker films, resulting in differently n-doped regions across the thick MAPbI3 films. We suggest that due to these differently n-doped regimes, an internal electric field is formed. Side-selective time-resolved microwave photo conductivity measurements show an elongation of the charge carrier lifetimes on increasing thickness. These observations can be explained by the fact that excess carriers separate under the influence of the electric field, preventing rapid decay in the thick films.
AB - Co-evaporation of metal halide perovskites by thermal evaporation is an attractive method since it does not require harmful solvents and enables precise control of the film thickness. Furthermore, the ability to manipulate the Fermi level allows the formation of a graded homojunction, providing interesting opportunities to improve the charge carrier collection efficiency. However, little is known about how these properties affect the charge carrier dynamics. In this work, the structural and optoelectronic properties of co-evaporated MAPbI3 films varying in thickness (100, 400, and 750 nm) with a gradient in composition are analyzed. The X-ray diffraction patterns show that excess PbI2 is only present in the thick layers. From X-ray photoelectron spectroscopy depth analysis, the I/Pb atomic ratio indicates methylammonium iodide deficiencies that become more prominent with thicker films, resulting in differently n-doped regions across the thick MAPbI3 films. We suggest that due to these differently n-doped regimes, an internal electric field is formed. Side-selective time-resolved microwave photo conductivity measurements show an elongation of the charge carrier lifetimes on increasing thickness. These observations can be explained by the fact that excess carriers separate under the influence of the electric field, preventing rapid decay in the thick films.
KW - charge carrier dynamics
KW - co-evaporation
KW - metal halide perovskites
KW - physical vapor deposition
KW - time-resolved microwave conductivity
UR - http://www.scopus.com/inward/record.url?scp=85131674314&partnerID=8YFLogxK
U2 - 10.1021/acsaem.2c00664
DO - 10.1021/acsaem.2c00664
M3 - Article
AN - SCOPUS:85131674314
SN - 2574-0962
VL - 5
SP - 7049
EP - 7055
JO - ACS Applied Energy Materials
JF - ACS Applied Energy Materials
IS - 6
ER -