Dual-passivation strategy on CsPbI2Br perovskite solar cells for reduced voltage deficit and enhanced stability. (1st December 2022)

• Record Type: Journal Article
• Authors: Li, Hui; Wang, Zhongxiao; Wang, Lian; Chang, Bohong; Liu, Zhen; Pan, Lu; Wu, Yutong; Yin, Longwei
• Is Part Of: Nano energy. Volume 103(2022)Part A
• Publication Date: 2022-12-01
• Subjects: CsPbI2Br -- Voltage deficit -- Dual-passivation -- Gradient band alignment -- Stability; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2022.107792
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: The notorious defects in the grain boundaries (GBs) and surfaces trigger serious nonradiative recombination and interfacial charge losses, concomitantly exacerbating the deterioration of photovoltaic performance and phase stability of CsPbI2 Br perovskite solar cells. In this work, a comprehensive dual-passivation strategy enabled by formamidine salts (FADP) is developed to annihilate defects both inside the GBs and over the surface. It is shown that formamidinothiourea (FATU) additive could effectively modulate crystallization and afford to passivate both shallow-/deep-level defects at GBs, thereby endowing CsPbI2 Br films with reduced lattice micro-strains and enlarged grains over 2 µm. Meanwhile, formamidinium bromine (FABr) post-treatment can efficiently heal the defective surface and realize cationic exchange with below CsPbI2 Br films, forming a gradient band alignment at the CsPbI2 Br/HTL interface. Profiting from ameliorated crystallization, inhibited GBs/surface charge recombination and facilitated hole transport ability, the novel FADP strategy substantially lifts the V oc from 1.22 V to 1.34 V, yielding a champion PCE of 16.74% with greatly reduced hysteresis. Coincidently, the unencapsulated FADP devices maintained 86.2% of initial PCE after aging at 25% RH for 40 days and 83.8% after 480 h aging under continuous illumination, which is pertinent to the inhibited defective region as well as Br-rich surface. Graphical Abstract: ga1 Highlights: A dual-passivation strategy enabled by formamidine salts is introduced to passivate defects both inside GBs and over the surface. Formamidinothiourea additive enables high-quality films while FABr post-treatment forms gradient band alignment at CsPbI2 Br/HTL interface. V oc increases from 1.22 V to 1.34 V and a power-conversion-efficiency of 16.74% is achieved. The unencapsulated devices behave excellent humidity- and light- stability.