Chlorobenzenesulfonic Potassium Salts as the Efficient Multifunctional Passivator for the Buried Interface in Regular Perovskite Solar Cells

Abstract

The interfacial properties for the buried junctions of the perovskite solar cells (PSCs) play a crucial role for the further enhancement of the power conversion efficiency (PCE) and stability of devices. Delicate manipulation of the interface properties such as the defect density, energy alignment, perovskite film quality, etc., guarantees efficient extraction and transport of photogenerated carriers. Herein, chlorobenzenesulfonic potassium salts are presented as a novel multifunctional agent to modify the buried tin oxide (SnO2)/perovskite interface for regular PSCs. The increasing number of carbon‐chlorine bonds (CCl) in 2,4,5‐trichlorobenzenesulfonic potassium (3Cl‐BSAK) exhibit efficient interaction with uncoordinated Sn, effectively filling oxygen vacancies in the SnO2 surface. Importantly, synergistic effects of the functional group‐rich organic anions and the potassium ion are achieved for reduced defect density, carrier recombination, and hysteresis. A champion PCE of 24.27% and the open‐circuit voltage (VOC) up to 1.191 V for modified devices are obtained. The unencapsulated devices maintain 80% of their initial PCE after aging at 80 °C for 800 h in the atmosphere and 95% after aging for 100 d. With 3Cl‐BSAK decoration, a high efficiency semitransparent PSC with a PCE of 12.83% and an average visible light transmittance (AVT) over 27% is also obtained.

Fluorinated Interfaces for Efficient and Stable Low‐Temperature Carbon‐Based CsPbI2Br Perovskite Solar Cells

“…The former is related to the absorption of transient species, [50] while the later can be attributed to the ground state bleaching and stimulated emission of the perovskite films. [38] Compared with reference sample, the PB negative peak intensity obviously decreased in KTFA modified sample, further confirming that KTFA contributes to the exciton transition and electron extraction from CsPbI 2 Br into SnO 2 . [51][52][53][54] Furthermore, the kinetic decay traces of PB negative peaks were fitted, as shown in Figure S12 and Table S6 (Supporting Information).…”

“…This will lead to the wetting interface for perovskite and reduce Gibbs free energy of heterogeneous nucleation. [38] The reduced roughness and improved wettability facilitate the uniform nucleation and crystallization of perovskite films, thus resulting in full surface coverage. [39] Then, the influence of KTFA modification on the optoelectronic properties of SnO 2 film was systematically studied.…”

Revealing Steric‐Hindrance‐Dependent Buried Interface Defect Passivation Mechanism in Efficient and Stable Perovskite Solar Cells with Mitigated Tensile Stress

“…The defects at buried interface, which originate from not only the lower surface of perovskite films, but also the upper surface of SnO 2 films, are one of the main reasons for the nonradiative recombination loss of interfacial carriers. [14][15][16] The rapid crystal lization process would lead to the generation of a large number of defects in polycrystalline perovskite films, which usually dis tribute at grain boundary (GB) and interface. [17][18][19] These defects are usually deep level defects, which would bring about serious carrier nonradiative recombination and thus deteriorate device performance.…”

“…In addition, there are often a mass of oxygen vacancy defects on the surface of SnO 2 ETL, which would reduce its electron extraction and transport efficiencies, causing carrier nonradiative recombination and thereby decreasing device photovoltaic performance. [11,15,16,20] The residual strain induced by stress usually exists in perovskite films, which can be classified into compressive and tensile strain. The strain produced in perovskite films could be ascribed to many fac tors, such as coefficient of thermal expansion (CTE) difference between perovskites and charge transport materials (CTMs), lattice mismatch between perovskite film and substrate, tem perature gradient, light/bias stimulation, phase transitions, and GBs.…”

“…[26] Zhao et al incorporated CsI into SnO 2 ETL and revealed that inter facial defect passivation, perovskite crystal growth promotion, improved band alignment, and enhanced UV stability were achieved simultaneously after CsI modification for buried inter face. [14] The chlorobenzenesulfonic potassium salts (3ClBSAK) was employed by Zhong et al [16] manipulate SnO 2 /perovskite buried interface, which enabled the realization of interfacial defect passivation and suppressed nonradiative recombination along with reduced hysteresis. Although remarkable advance ments have been accomplished, the above reported interface molecules usually only can passivate the defects at buried inter face but can not release interfacial stress.…”