Metal-free chiral molecular ferroelectric photovoltaics
Shulin Jiao, Haidong Jiang, Chang‐Chun Fan, Cuiping Xu, Junjie Jiang, Yanming Xu, Zheng Tang, Xiaofan Sun, Peiqi Ji, Xingming Yang, Kongmeng Ye, Libo Xu, Qi You, Shuang Chen, Hong‐Ling Cai, Xiaoshan Wu
Abstract
Ferroelectric semiconductors have gained significant attraction for designing photovoltaic devices. However, their wide bandgap results in poor absorption of visible light. Herein, we report a pair of chiral metal-free molecular ferroelectric semiconductors (1 R ,4 R /1 S ,4 S - C 5 H 10 NO)I 3 ( R/S-OABHI ; (1 R ,4 R /1 S ,4 S - C 5 H 10 NO) + = 1 R ,4 R /1 S ,4 S -2-oxa-5-azabicyclo[2.2.1]heptonium) with notable ferroelectricity (saturation polarization of ∼6.8 and 6.1 μC/cm 2 for R-/S-OABHI , respectively). They demonstrate an appropriate photovoltaic bandgap of ∼ 1.41 and 1.39 eV for R-/S-OABHI , respectively, comparable to MAPbI 3 (MA = methylammonium). Experiments and computational simulations reveal that the ferroelectricity of R / S-OABHI originates from their non-centrosymmetric crystal packing in a controllable helical manner, while the I 3 − contributes to band edges. Meanwhile, photovoltaic effect is firstly observed in the R-OABHI based solar cell with an open-circuit voltage of 0.581 V and a short-circuit current density of 1.734 mA/cm 2 . Overall, we establish a new approach for realizing metal-free ferroelectric photovoltaics, and it will pave the way for the exploration of multifunctional chiral molecular ferroelectrics.