Judicious inhibition of interfacial non-radiative recombination via chlorine-isomerized self-assembled molecules for efficient and durable organic solar cells

Moderate charge transporting capacity together with inexpedient energetic level alignment of the self-assembled molecules (SAMs) initiate severely interfacial non-radiative recombination in organic solar cells (OSCs), which significantly hinder the performance and robustness of corresponding devices. Herein, a molecular isomerization strategy is developed to construct promising SAM for efficient and reliable OSC devices, where chlorine atoms are grafted on either para- (pCl-ph) or meta- (mCl-ph) location in benzene sidechain substituted carbazole terminal group. In comparison with para location, we found the meta-Cl substation can instigate the intermolecular interaction and further boost molecular packing, which is beneficial to strengthen the carrier conductivity and ameliorate the trap density. Furthermore, the optimal work function tunability of mCl-ph trigger the favorable energy-level layout, whereas over deep-lying level arrangement of pCl-ph induced the circumferential charge accumulation and further catalyze the insufferable non-radiative recombination loss. Consequently, the champion power conversion efficiency (PCE) is upgraded from 16.1 % (pCl-ph) to 19.6 % (mCl-ph) with superior generality in diverse blend system. More strikingly, the raised operation stability (T80:575 h) is harvested in mCl-ph devices (pCl-ph devices T80:111 h), demonstrating that SAM isomerization is an appealing approach for OSCs with high efficiency and stability simultaneously.