Rational design of dipolar chromophore as an efficient dopant-free hole-transporting material for perovskite solar cells

In this paper, an electron donor-acceptor (D-A) substituted dipolar chromophore (<b>BTPA-TCNE</b>) is developed to serve as an efficient dopant-free hole-transporting material (HTM) for perovskite solar cells (PVSCs). <b>BTPA-TCNE</b> is synthesized via a simple reaction between a triphenylamine-based Michler’s base and tetracyanoethylene. This chromophore possesses a zwitterionic resonance structure in the ground state, as evidenced by X-ray crystallography and transient absorption spectroscopies. Moreover, <b>BTPA-TCNE</b> shows an antiparallel molecular packing (i.e., centrosymmetric dimers) in its crystalline state, which cancels out its overall molecular dipole moment to facilitate charge transport. Finally, <b>BTPA-TCNE</b> can be employed as an effective dopant-free HTM to realize an efficient (PCE ≈ 17.0%) PVSC in the conventional n-i-p configuration, outperforming the control device with doped spiro-OMeTAD HTM.. Authors: Li, Zhong’an [Univ. of Washington, Seattle, WA (United States); University of Washington]; Zhu, Zonglong [Univ. of Washington, Seattle, WA (United States)]; Chueh, Chu -Chen [Univ. of Washington, Seattle, WA (United States)]; Jo, Sae Byeok [Univ. of Washington, Seattle, WA (United States)]; Luo, Jingdong [Univ. of Washington, Seattle, WA (United States)]. DOE Contract: EE0006710. Subjects: 14 SOLAR ENERGY; 36 MATERIALS SCIENCE