Designing Effective Hole Transport Layers in Tin Perovskite Solar Cells

Beyond collecting hole charge carriers,
hole transport
layers (HTLs)
in perovskite solar cells (PSCs) can play a significant role in determining
the perovskite’s quality and stability. While diverse prospective
HTL materials are explored for high-performance lead-based PSCs, tin-based
PSCs predominantly rely on poly(3,4-ethylenedioxythiophene) polystyrenesulfonate
(PEDOT:PSS) to achieve power conversion efficiency near 15% and around
1 year of N2 shelf-storage stability. While tin perovskites
exhibit distinct characteristics in terms of crystal defect species,
interfacial properties, crystallization mechanisms, and shallow energy
levels, device architectures and HTL materials are usually adopted
from lead PSCs without tailoring them for tin PSCs. In this regard,
the effective design of HTLs in tin PSCs remains not well-explored.
In this Perspective, we propose a comprehensive set of effective HTL
design factors with a dedicated focus on tin PSCs, aiming at upgrading
PEDOT:PSS and modifying other prospective HTLs to ultimately break
the current performance limit to be competitive with or beyond lead
PSCs.