Abstract
Methylammonium lead triiodide (CH3NH3PbI3/MAPbI3) is the most intensively explored perovskite light-absorbing material for hybrid organic–inorganic perovskite photovoltaics due to its unique optoelectronic properties and advantages. This includes tunable bandgap, a higher absorption coefficient than conventional materials used in photovoltaics, ease of manufacturing due to solution processability, and low fabrication costs. In addition, the MAPbI3 absorber layer provides one of the highest open-circuit voltages (Voc), low Voc loss/deficit, and low exciton binding energy, resulting in better charge transport with decent charge carrier mobilities and long diffusion lengths of charge carriers, making it a suitable candidate for photovoltaic applications. Unfortunately, MAPbI3 suffers from poor photochemical stability, which is the main problem to commercialize MAPbI3-based perovskite solar cells (PSCs). However, researchers frequently adopt additive engineering to overcome the issue of poor stability. Therefore, in this review, we have classified additives as organic and inorganic additives. Organic additives are subclassified based on functional groups associated with N/O/S donor atoms; whereas, inorganic additives are subcategorized as metals and non-metal halide salts. Further, we discussed their role and mechanism in terms of improving the performance and stability of MAPbI3-based PSCs. In addition, we scrutinized the additive influence on the morphology and optoelectronic properties to gain a deeper understanding of the crosslinking mechanism into the MAPbI3 framework. Our review aims to help the research community, by providing a glance of the advancement in additive engineering for the MAPbI3 light-absorbing layer, so that new additives can be designed and experimented with to overcome stability challenges. This, in turn, might pave the way for wide scale commercial use.
Highlights
Alternative renewable energy sources are considered reliable options for long-term usage due to the limited availability of traditional energy resources
The poor intrinsic and extrinsic stability causes a restriction in the substantial commercialization of the perovskite solar cells (PSCs)
Intrinsic instability is considered due to the presence of under-coordinated Pb sites or escape of a volatile product or formation of molecular iodine; either of these creates a defect in the perovskite surface
Summary
Alternative renewable energy sources are considered reliable options for long-term usage due to the limited availability of traditional energy resources (i.e., coal, oil, and gas). In the presence of light and heat, the identified degradation pathways are presented in Equations (8) and (9) [2,17,18,19,20,21,22,23]: CH3NH3PbI3 → [PbI2] + volatile species (rising from CH3NH3I) These Pb and iodine sites create defect sites/trap states, resulting in instability of the CH3NH3PbI3 active layer and CH3NH3PbI3-based perovskite solar cell devices overall. This review aims to analyze the research progress/advancement in the context of additives employed to improve the performance and stability of the CH3NH3PbI3 photoactive light-absorbing layer This can further help design additives, resolving stability challenges to commercialize the CH3NH3PbI3-based perovskite solar cell
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