Highly Stable Thiophene Perovskite Enabled by an Oxygen-Containing Moiety for Efficient Photovoltaics

We
present oxygen-containing 2D perovskites, ((TPM)x(TFF)1–x)2(CH3NH3)n−1PbnI3n+1 (TPM
= C4SH3CH2NH3, TFF = C4OH7CH2NH3, x = 0.5 or 0.75, and n = 1–4), which have
two species of cations between the inorganic slab. The 2D layered
(TPM)2(CH3NH3)n−1PbnI3n+1(n = 1–4) perovskites have a high
polarizability of the sulfur atom and a π-conjugated electron-rich
aromatic ring structure. However, it still shows instability under
ambient condition. The 2D (TPM)2(CH3NH3)n−1PbnI3n+1(n = 1–4)
perovskites incorporated an oxygen-containing molecule, TFF, which
has high durability toward the environmental system. Structural characterization
by single-crystal X-ray diffraction reveals that the ((TPM)x(TFF)1–x)2(CH3NH3)n−1PbnI3n+1 perovskites
exhibit a slight structural distortion of the equatorial Pb–I–Pb
bond angles compared to those in the (TPM)2(CH3NH3)n−1PbnI3n+1 (n = 1–4) perovskites. However, their band gaps are almost the
same, because the interlayer spacing between the inorganic layers
for the TPM and TFF compounds has approximately the same spatial distance.
Furthermore, it was observed that the long emission lifetime in the
((TPM)x(TFF)1–x)2(CH3NH3)n−1PbnI3n+1 perovskite series from the self-trapped excitons is due
to the more distorted structure. We fabricated photovoltaic devices
that utilize these materials as light absorbers, and they exhibit
promising performances with the highest power conversion efficiency
of 10.01% for (TPM0.75TFF0.25)2(MA)3Pb4I13-based devices.