No abstract

Interfacial trap-assisted non-radiative recombination and residual stress impede the further increase of power conversion efficiency (PCE) and stability of the methylammonium-free (MA-free) perovskite solar cells (PSCs). Here, we report an interfacial defect passivation and stress release strategy through employing the multi-active-site Lewis base ligand (i.e., (5-mercapto-1,3,4-thiadiazol-2-ylthio)­acetic acid (MTDAA)) to modify the surface and grain boundaries (GBs) of MA-free perovskite films. Both experimental and theoretical results confirm strong chemical interactions between multiple active sites in the MTDAA molecule and undercoordinated Pb2+ at the surface or GBs of perovskite films. It is demonstrated theoretically that multi-active-site adsorption is more favorable thermodynamically as compared to single-active-site adsorption, regardless of PbI2 termination and formamidinium iodide (FAI) termination types. MTDAA modification results in much reduced defect density, increased carrier lifetime, and almost thoroughly released interfacial residual stress. Upon MTDAA passivation, the PCE is boosted from 20.26% to 21.92%. The unencapsulated device modified by MTDAA maintains 99% of its initial PCE after aging under the relative humidity range of 10–20% for 1776 h, and 91% after aging at 60 °C for 1032 h.

Bulk and interfacial nonradiative recombination hinders the further enhancement of power conversion efficiency (PCE) and stability of SnO2-based planar perovskite solar cells (PSCs). To date, it is still a huge...

Interface engineering is one feasible and effective approach to minimize the interfacial nonradiative recombination stemming from interfacial defects, interfacial residual stress, and interfacial energy level mismatch. Herein, a novel and effective steric-hindrance-dependent buried interface defect passivation and stress release strategy is reported, which is implemented by adopting a series of adamantane derivative molecules functionalized with CO (i.e., 2-adamantanone (AD), 1-adamantane carboxylic acid (ADCA), and 1-adamantaneacetic acid (ADAA)) to modify SnO 2 /perovskite interface. All modifiers play a role in passivating interfacial defects, mitigating interfacial strain, and enhancing device performance. The steric hindrance of chemical interaction between CO in these molecules and perovskites as well as SnO 2 is determined by the distance between CO and bulky adamantane ring, which gradually decreases from AD, ADCA, and ADAA. The experimental and theoretical evidences together confirmed steric-hindrance-dependent defect passivation effect and interfacial chemical interaction strength. The interfacial chemical interaction strength, defect passivation effect, stress release effect and thus device performance are negatively correlated with steric hindrance. Consequently, the ADAA-modified device achieves a seductive efficiency up to 23.18%. The unencapsulated devices with ADAA maintain 81% of its initial efficiency after aging at 60 °C for 1000 h.

Perovskite solar cells suffer from poor reproducibility due to the degradation of perovskite precursor solution. Herein, we report an effective precursor stabilization strategy via incorporating 3-hydrazinobenzoic acid (3-HBA) containing carboxyl (À COOH) and hydrazine (À NHNH 2 ) functional groups as stabilizer. The oxidation of I À , deprotonation of organic cations and amine-cation reaction are the main causes of the degradation of mixed organic cation perovskite precursor solution. The À NHNH 2 can reduce I 2 defects back to I À and thus suppress the oxidation of I À , while the H + generated by À COOH can inhibit the deprotonation of organic cations and subsequent amine-cation reaction. The above degradation reactions are simultaneously inhibited by the synergy of functional groups. The inverted device achieves an efficiency of 23.5 % (certified efficiency of 23.3 %) with an excellent operational stability, retaining 94 % of the initial efficiency after maximum power point tracking for 601 hours.