Drawbacks like serious interface defects, imperfect energy level arrangement and uncontrollable perovskite
nucleation hinder further improvement to achieve efficient and stable planar perovskite sollar cells (PSCs), which
fortunately can be solved by interface modification with small molecules. However, it is still a challenge to
develop more simple and efficient multi-functional small molecules to simultaneously solve these problems.
Herein, conjugated small molecule 3-thiophenboric acid (TBA) was utilized for the first time at the SnO2/
perovskite interface to achieve this goal. With the dipole moment of TBA, the energy level arrangement between
SnO2 and perovskite is optimized. Defects at both sides of the interface are passivated by functional groups on
TBA effectively, inhibiting the non-radiative recombination and reducing the energy loss. Besides, the quality of
perovskite film is improved due to inhibited disordered heterogeneous nucleation. As a result, the open voltage
(VOC), short current density (JSC) and fill factor (FF) are all improved, which leads to a champion device with PCE
up to 21.80%, much higher than 19.74% of control one. In addition, our optimized devices show excellent
stability when storing for a long time, aging under high humidity and under continuous illumination. Our results
provide a novel strategy to improve the efficiency and stability of PSCs synergistically by multi-functional
conjugated small molecule.