RESUMEN
Perovskite solar cells (PSCs) have been significantly improved by utilizing an inorganic hole-transporting layer (HTL), such as nickel oxide. Despite the promising properties, there are still limitations due to defects. Recently, research on self-assembled monolayers (SAMs) is being actively conducted, which shows promise in reducing defects and enhancing device performance. In this study, we successfully engineered a p-i-n perovskite solar cell structure utilizing HC-A1 and HC-A4 molecules. These SAM molecules were found to enhance the grain morphology and uniformity of the perovskite film, which are critical factors in determining optical properties and device performance. Notably, HC-A4 demonstrated superior performance due to its distinct hydrophilic properties with a contact angle of 50.3°, attributable to its unique functional groups. Overall, the HC-A4-applied film exhibited efficient carrier extraction properties, attaining a carrier lifetime of 117.33 ns. Furthermore, HC-A4 contributed to superior device performance, achieving the highest device efficiency of 20% and demonstrating outstanding thermal stability over 300 h.
RESUMEN
Perovskite solar cells (PSCs) have been receiving considerable attention as next-generation solar cells. However, their short lifetime is a major obstacle to their commercialization. In addition to the properties of the materials used in PSCs, their interfaces play an important role in device stability by maintaining their initial design. In this study, we developed a transition-metal dichalcogenide (TMD) as a stable and efficient interlayer. MoS2 and WSe2 were applied to both the hole and electron transport sides of the PSCs with general FTO/TiO2/MAPbI3/Spiro-OMeTAD/Au structures, respectively. Owing to efficient charge transfer by TMD interlayers, our PSCs achieved a 19.24% efficiency, which is higher than the efficiency of the control devices (18.22%). Furthermore, the device stability was markedly improved by the passivation and strain-release effects of the TMD interlayers. Thus, the PSCs with TMD interlayers demonstrated a stable performance over 1000 h under damp heat (85 °C and 85% relative humidity) conditions.
RESUMEN
Recent studies have demonstrated that copper (I) thiocyanate (CuSCN) has huge potential as a hole extraction material (HEM) for perovskite solar cells. Here, we used CuSCN as a HEM and analyzed its relationships with a methylammonium lead iodide (MAPbI3) perovskite layer. The CuSCN dissolved in diethyl sulfide (DES) was spin-coated on the MAPbI3 layer. For high-quality and dense CuSCN layers, post-annealing was carried out at various temperatures and times. However, the unwanted dissociation of MAPbI3 to PbI2 was observed due to the post-annealing for a long time at elevated temperatures. In addition, DES, which is used as a CuSCN solvent, is a polar solvent that damages the surface of MAPbI3 perovskites and causes poor interfacial properties between the perovskite layer and HEM. To solve this problem, the effect of the molar ratio of methylammonium iodide (MAI) and PbI2 in the MAPbI3 precursor solution was investigated. The excess MAI molar ratio in the MAPbI3 precursor solution reduced MAPbI3 surface damage despite using DES polar solvent for CuSCN solution. In addition, dissociation of MAPbI3 to PbI2 following an adequate post-annealing process was well suppressed. The excess MAI molar ratio in the MAPbI3 precursor could be compensated for the MA loss and effectively suppress phase separation from MAPbI3 to MAI + PbI2 during post-annealing. The efficiency based on the normal planar structure of CuSCN/MAPbI3 (using excess MAI)/TiO2 was approximately 17%. The CuSCN-based MAPbI3 device shows more optimized stability than the conventional spiro-OMeTAD under damp heat (85 °C and 85% relative humidity) conditions because of the robust inorganic HEM.
