Residual PbI₂ Beneficial in the Bulk or at the Interface? An Investigation Study in Sputtered NiO_x Hole-Transport-Layer-Based Perovskite Solar Cells

Abstract

Investigation of the perovskite (MAPbI3; MA+ = CH3NH3 +) crystallization, location of residual lead iodide (PbI2), and its influence on the optoelectronic and photovoltaic properties is important to resolve the low-efficiency issue in radio frequency (RF) sputtered nickel oxide (sp-NiO x ) based perovskite solar cells (PSCs). Despite obtaining the perovskite layer from a solution of the stoichiometric ratio of precursor materials using a one-step method (OSM) for spin-coating, residual PbI2 grains are observed (from the top surface scanning electron microscopy (SEM) image) in the bulk of perovskite (deposited on sp-NiO x ). To investigate the dependence of residual PbI2 on the preparation methods, we prepared the perovskite (on sp-NiO x ) by a two-step method (TSM) in which methylammonium iodide (MAI) solution is spin-coated on top of the deposited PbI2 layer. The cross-sectional SEM image of the TSM-based perovskite device, confirms the presence of the residual PbI2 layer (20–50 nm) at the interface of perovskite/NiO x . Although a higher X-ray diffraction (XRD) peak intensity of residual PbI2 was observed, the higher crystallinity of the perovskite film prepared by TSM was confirmed based on the evaluation of the photoluminescence (PL) peaks and the PL lifetime. In comparison with the devices prepared by OSM, the higher photovoltaic performance of PSCs is observed for devices fabricated using TSM. An investigation on the relation of the device performance with the location of residual PbI2 is presented in this work and can be insightful to further improve the performance of sp-NiO x -based PSCs.

From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co‐Evaporated Perovskite Solar Cells

“…However, based on the needle-like structure of these segregations, a PbI 2 -rich character is assumed here as has been previously reported. [80][81][82][83] Despite some uncertainties about the exact nature of these segregations, a rather detrimental influence is expected. Moreover, the size and shape of perovskite crystals on PTAA appear more homogeneous and well defined.…”

Concerted Ion Migration and Diffusion‐Induced Degradation in Lead‐Free Ag3BiI6 Rudorffite Solar Cells under Ambient Conditions

“…A blueshift in the PL peak (Figure S13b, Supporting Information) was correspondingly observed for Ag 3 BiI 6 film processed with antisolvent. The exact reason for the enhanced PL peak intensity and blueshift is not known at the moment, but it might be due to low trap/defect sites and recombination centers [36,37] in the bulk of Ag 3 BiI 6 and/or could also be within the experimental error mostly because of the existence of impure phase or multiphase features. In addition to this, the PL showed a small additional peak at around %735 nm which can be ascribed to the Ag 3 BiI 6 impure phase (presence of residual AgI) and/or multiphase features.…”

Inorganic top electron transport layer for high performance inverted perovskite solar cells

“…In addition, Al, In and Ga doped ZnO are also promising for electron transporting in inverted PSCs. 5,6,42,60,121,147,148,153,170,[220][221][222][223] The reported inorganic materials used as ETM are summarized in Table 1.…”

“…Al doped ZnO (ZAO) with better properties than pristine ZnO has been widely used as top ETL in inverted PSCs. 5,6,42,60,121,147,148,153,170 Shown in Figure 4, Al doping enhanced the properties of pristine ZnO, such as transmittance, conductivity, and thus improve the device performance. Similarly, In References 151,220 and Ga 221,222 have also been applied as dopants in ZnO and used as efficient top ETL in inverted PSCs.…”

“…2 Although the PCE value is some lower, inverted PSCs have some special advantages, such as much lower hysteresis and promising application on tandem solar cells, which makes them a famous star among the new-generation photovoltaic devices. [3][4][5] As an important functional layer in high performance inverted PSC, electron transport layer on top of perovskite film (namely top ETL) play an irreplaceable role. Known to be a star ETL, fullerene and it derivative such as [6,6]phenyl-C61-butyric acid methyl ester (PCBM) has been widely used in inverted PSCs, exhibiting negligible hysteresis.…”