Bumjin Gil

As for the commonly used formamidinium lead iodide (FAPbI₃) perovskite, adding small amount of larger organic cations is a viable strategy to overcome its instability caused by formamidinium (FA) or iodide (I). Herein, FAPbI₃ perovskite is modified by addition of quaternary cation phenyltrimethylammonium (PTMA), which forms 2D perovskite phase. With the presence of PTMA cations and small‐sized Br anions, the local strain of perovskite layer is mitigated. Also, X‐ray analyses reveal that PTMA cation directs FAPbI₃ to have more vertically oriented structure, which aids the enhanced photocarrier generation and extraction. Defect analyses suggest that PTMA bromide alloying also greatly reduces the trap sites. Due to these combined effects, the PTMABr‐modified device results in the improved open‐circuit voltage plus stability under 60 °C or 1 sun illumination, maintaining 80% of its initial efficiency after 1800 and 1400 h, respectively.

Perovskite solar cells (PSCs) are gaining significant interest as the future of photovoltaics owing to their superior performance and cost-effectiveness. Nevertheless, traps in PSCs have emerged as issues that adversely affect the efficiency and stability of the devices. In this study, the methylammonium chloride (MACl) additive and phenyltrimethylammonium iodide (PTMAI) posttreatment were applied to passivate bulk and surface defects. Furthermore, variations of the traps' quantitative spatial arrangement have been monitored by using the drive-level capacitance profiling (DLCP) analysis. A similar magnitude of trap reduction was observed for the bulk perovskite layer and two interfaces (electron transport layer (ETL)/perovskite and hole transport layer (HTL)/perovskite) with an optimal concentration of the MACl additive. However, the effect of perovskite posttreatment in reducing the trap density was much more noticeable at the HTL/perovskite interface compared to the bulk and ETL/perovskite regions. This observation was reinforced by the outcomes of the 500 h thermal stability tests at 60 °C from seven independent batches, which demonstrated a substantial suppression of trap accumulation, particularly at the HTL/perovskite interface, by an order of magnitude.

Perovskite solar cells (PSCs) are in the spotlight as promising renewable energy devices by their appealing properties. However, they face challenges both in power conversion efficiency (PCE) and long‐term stability. The presence of surface defects in the PSCs is a significant obstacle to achieving both high efficiency and stability, as these defects cause nonradiative recombination and degradation. Herein, a novel double‐side surface passivation method using phenyltrimethylammonium iodide (PTMAI) salt is applied to remove electronic defects effectively. Furthermore, double‐side passivation with PTMAI contributes to the enhancement of the perovskite crystallinity with the relaxed non‐uniform distribution of local strains. Finally, the efficiency of PSC is significantly improved by double‐side passivation with PTMAI, achieving a PCE of 21.87%. Furthermore, the passivated cell exhibited enhanced long‐term stability, maintaining over 80% of initial PCE after 1860 and 1030 h under 60 °C and 1 sun illumination, respectively.

In order to realize both efficient and stable perovskite solar cells, designing electron transport layer (ETL) is of crucial importance to withstand constant light illumination and thermal stress while maintaining high charge extractability. Herein, commonly used SnO₂ nanoparticle‐based ETL for perovskite solar cells is modified by ionic‐salt ammonium chloride (NH₄Cl) and tin chloride dihydrate (SnCl₂∙2H₂O) as additives, which is easily fabricated by simple one‐step spin coating of single precursor solution. With the presence of these dual additives at the ETL, the crystallinity of the upper perovskite layer is clearly enhanced. Defect analyses on the devices suggest that these modifications can effectively passivate trap sites that reside within the ETL and at the perovskite interfaces with the carrier‐transport layers. As a result, the modified SnO₂ ETL results in an improvement of device stability under thermal or light stress condition, maintaining over 80% of its initial efficiency after ≈2000 h storage under elevated temperature (85 °C) and after ≈2400 h of operation under 1 sun illumination.

Because of the facile formation of defects in organometal halide perovskites, the defect passivation has become an important prerequisite for the stable and efficient perovskite solar cell (PSC). Regarding that ionic defects of the perovskites play a significant role on the performance and stability of PSCs, we introduce lithium fluorides as effective passivators based on their strong ionic characteristics and small ionic radii. Both Li⁺ and F^– are observed to successfully incorporate within the perovskite layer, improving the device performances with the best efficiency over 20%, while the hysteresis effects are significantly reduced, confirming the passivation of perovskite defects. Moreover, LiF restrains both thermal degradation and photodegradation of PSCs, where over 90% of the initial efficiencies have been retained by LiF-incorporated devices for more than 1000 h under either 1 sun illumination or 85 °C thermal condition. As the trap density of states is analyzed before and after the thermal stress, not only the mitigation of electronic traps as fabricated but also the dramatic relaxation of traps during the postannealing step is observed with the LiF incorporation. From this work, LiF has shown its potential as a promising ionic passivator, and the phenomenal achievement of device stability by LiF provides a clear insight to overcome the stability issues of PSCs, a key to the commercialization of next-generation photovoltaics.

High-mobility inorganic CuCrO₂ nanoparticles are co-utilized with conventional poly(bis(4-phenyl)(2,5,6-trimethylphenyl)amine) (PTAA) as a hole transport layer (HTL) for perovskite solar cells to improve device performance and long-term stability. Even though CuCrO₂ nanoparticles can be readily synthesized by hydrothermal reaction, it is difficult to form a uniform HTL with CuCrO₂ alone due to the severe agglomeration of nanoparticles. Herein, both CuCrO₂ nanoparticles and PTAA are sequentially deposited on perovskite by a simple spin-coating process, forming uniform HTL with excellent coverage. Due to the presence of high-mobility CuCrO₂ nanoparticles, CuCrO₂/PTAA HTL demonstrates better carrier extraction and transport. A reduction in trap density is also observed by trap-filled limited voltages and capacitance analyses. Incorporation of stable CuCrO₂ also contributes to the improved device stability under heat and light. Encapsulated perovskite solar cells with CuCrO₂/PTAA HTL retain their efficiency over 90% after ~900-h storage in 85 °C/85% relative humidity and under continuous 1-sun illumination at maximum-power point.