Cesium Iodide Incorporation in Tin Oxide Electron Transport Layer for Defect Passivation and Efficiency Enhancement in Double Cation Absorber‐Based Planar Perovskite Solar Cells

Abstract

Fermi level tuning and defect passivation at the electron selective layer (ESL)/perovskite interface has a strong effect on the perovskite solar cell (PSC) device performance. Two strategies are commonly used for passivation, 1) bulk passivation—by adding dopants in the ESL and 2) surface passivation—to suppress the interface dangling bonds using ligands. Herein, a novel dual passivation (bulk and surface) strategy is presented by incorporating a simple molecule cesium iodide (CsI) in the SnO x ESL. Passivation effects using different CsI dopant concentrations (0–10 wt%) in SnO x solution were studied and its beneficial role of defect passivation is discussed in detail. A systematic study revealed that the addition of CsI in the SnO x ESL not only significantly influences the open‐circuit voltage (V oc) and fill factor (FF), but also suppresses the recombination at the interface due to its improved built in surface potential. Lower trap‐filled limit voltage (V TFL), trap density (n t), and diode ideality factor (n id) are observed for the CsI incorporated SnO x ESL as compared with the bare SnO x layer which leads to a power conversion efficiency improvement from 14.3% to 15.4%.

Manganese Dopant-Induced Isoelectric Point Tuning of ZnO Electron Selective Layer Enable Improved Interface Stability in Cesium–Formamidinium-Based Planar Perovskite Solar Cells

“…Both ZnO and 5 wt % Mn:ZnO have a similar thickness of ∼30 nm which is responsible for the higher J sc reported in our work with the top perovskite layer (CsFAPbI 3 ) having a thickness of ∼550 nm on both ESLs. The thickness of the spiro-OMeTAD layer was ∼200 nm as previously reported in our earlier work . The optimum thickness of the perovskite layer is crucial for effective bulk charge transport from the perovskite to the ZnO interface, while relatively thinner and uniform ZnO layers are needed for effective charge carrier transport to the ITO layer, else dominant series resistance may be observed in J – V studies …”

“…The thickness of the spiro-OMeTAD layer was ∼200 nm as previously reported in our earlier work. 53 The optimum thickness of the perovskite layer is crucial for effective bulk charge transport from the perovskite to the ZnO interface, while relatively thinner and uniform ZnO layers are needed for effective charge carrier transport to the ITO layer, else dominant series resistance may be observed in J−V studies. 54 5.3.…”

Design and synthesis of multifaceted dicyanomethylene rhodanine linked thiophene: a SnOx–perovskite dual interface modifier facilitating enhanced device performance through improved Fermi level alignment, defect passivation and reduced energy loss

“…Weighted average transmittance (%WAT) was calculated using eqn (1) to quantify the effect of change in transmittance upon AA6 modification.where % T is the transmittance spectra of the measured samples, I AM1.5 is the AM 1.5 solar spectrum and λ is the measured wavelength of range 300 nm ( λ 1 ) to 800 nm ( λ 2 ). 37 For glass/ITO/SnO x , the %WAT was ∼85.9% and for 0.05, 0.1 and 0.2 mg mL −1 AA6 passivated SnO x layers, %WAT of ∼84.9%, ∼85.4% and ∼84.5% was observed respectively, which is a less than 2% drop compared to SnO x samples and this indicates that there is no adverse variation in %WAT with respect to AA6 passivation of SnO x . To further evaluate the effect of AA6 on %WAT, 1 mg mL −1 AA6 solution (in CHCl 3 ) was coated directly onto the glass/ITO substrate (without the SnO x layer) as shown in Fig.…”

“…This observation again reiterates that the AA6 molecule successfully passivates the SnO x surface defects and acts as a bridge between CsFAPbI 3 and SnO x , resulting in effective charge carrier transfer. 18,37 3.3 Device performance of the AA6 passivated SnO x based PSC…”

“…Similar PCE drops were observed in our previous reports that correlated very well with improved FF in low light intensities (0.2 sun), which justies the thicker spiro-OMeTAD layer that is causing the FF drop under one sun test conditions. 29,37,66 To further understand the V oc improvement upon AA6 passivation, the open circuit voltage loss (DV) for PSC devices was calculated using eqn (4), 67 where E g is the perovskite absorber bandgap (E g = 1.55 eV), q is the elementary charge and V oc is the PSC device open circuit voltage. For 0.1 mg mL −1 AA6…”