Multifunctional indaceno[1,2-b:5,6-b′]dithiophene chloride molecule for stable high-efficiency perovskite solar cells

The additive strategy has emerged as an effective approach to improving the performance of perovskite solar cells (PSCs). Herein, a small acceptor-donor-acceptor type molecule indaceno[1,2-b:5,6-b′]dithiophene chloride (IDT-Cl) is designed and synthesized to advance both the efficiency and stability of FA 0.85 MA 0.15 PbI 3 PSCs. Within the IDT-Cl molecule, the S-group with high electron density promotes chemical bonding with the lead cations in the perovskite, resulting in enlarged grain size and smoother surface topography of the perovskite absorber. In addition, the undercoordinated lead ions in the perovskite layer may be passivated by the carbonyl group in the 5-chloroindolin-2-one unit, thereby reducing the number of nonradiative recombination centers. Meanwhile, the IDT-Cl adjusts the energy level mismatch between the perovskite and two adjacent carrier transport layers, leading to easy charge collection. By the multifunctional effect of the IDT-Cl molecule, the modified device yields a high power conversion efficiency (PCE) of 24.46%, 8.8% higher than that of the control PSC (22.48%). More importantly, the hydrophobic alkyl side-chain of the IDT-Cl molecule further ensures enhanced humidity stability of the perovskite film and environmental, thermal, and light stabilities of the PSC devices.