  Tin perovskites are the most promising environmentally friendly alternative
to lead perovskites. Among tin perovskites, FASnI3 (CH4N2SnI3) shows optimum
band gap, and easy processability. However, the performance of FASnI3 based
solar cells is incomparable to lead perovskites for several reasons, including
energy band mismatch between the perovskite absorber film and the charge
transporting layers (CTLs) for both types of carriers, i.e., for electrons
(ETLs) and holes (HTLs). However, the band diagrams in the literature are
inconsistent, and the charge extraction dynamics are poorly understood. In this
paper, we study the energy band positions of FASnI3 based perovskites using
Kelvin probe (KP) and photoelectron yield spectroscopy (PYS) to provide a
precise band diagram of the most used device stack. In addition, we analyze the
defects within the current energetic landscape of tin perovskites. We uncover
the role of bathocuproine (BCP) in enhancing the electron extraction at the
fullerene C60/BCP interface. Furthermore, we used transient surface
photovoltage (tr-SPV) for the first time for tin perovskites to understand the
charge extraction dynamics of the most reported HTLs such as NiOx and PEDOT,
and ETLs such as C60, ICBA, and PCBM. Finally, we used Hall effect, KP, and
time-resolved photoluminescence (TRPL) to estimate an accurate value of the
p-doping concentration in FASnI3 and showed a consistent result of 1.5 * 1017
cm-3. Our findings prove that the energetic system of tin halide perovskites is
deformed and should be redesigned independently from lead perovskites to unlock
the full potential of tin perovskites.
