Future Research Directions in Perovskite Solar Cells: Exquisite Photon Management and Thermodynamic Phase Stability

Abstract

As power conversion efficiency (PCE) of perovskite solar cells (PSCs) has rapidly increased up to 25.7% in 2022, a curiosity about the achievable limit of the PCE has prevailed and demands understanding about the underlying fundamentals to step forward. Meanwhile, outstanding long‐term stability of PSCs over 1000 h has been reported at operating conditions or under damp heat test with 85 °C/85% relative humidity. Herein comes the question as to whether the phase stability issue of perovskite crystal is completely resolved in the most recent state‐of‐the‐art perovskite film or if it deceives everyone into believing so by significantly slowing the kinetics. On the one hand, the fundamental origins of a discrepancy between reported values and the theoretical limit are thoroughly examined, where the importance of light management is greatly emphasized with the introduction of external luminescence as a key parameter to narrow the gap. On the other hand, the phase stability of a perovskite film is understood from thermodynamic point of view to address viable approaches to lower the Gibbs free energy, distinguishing the kinetically trapped condition from the thermodynamically stable phase.

Effect of Zn(TFSI)2 on the performance-aging time of perovskite solar cells

“…Therefore, the overall higher R rec in figure 5(b) is in good accordance with the photovoltaic parameters in figure 5(a). The photogenerated hole tends to recombine at the interface more easily once it is transferred to the HTL, having lower mobility than the case where the hole remains in the perovskite bulk because the bulk recombination in perovskite is negligible based on its high defect tolerance [32,33]. In other words, the suppressed recombination at the perovskite/HTL interface by decreasing ∆E offset as well as passivating surface defects effectively counterbalances the low hole mobility of the HTL at the early stage of device aging.…”

High-Quality TiO2 Electron Transport Film Prepared via Vacuum Ultraviolet Illumination for MAPbI3 Perovskite Solar Cells

“…Perovskite solar cells (PSCs) stand out in the third generation of solar cells due to the advantages of perovskite, such as adjustable band gap, high absorption coefficient, long carrier lifetime, and high carrier mobility. − In the past more than ten years, the power conversion efficiency (PCE) of metal halide PSCs has been increased from 3.8 to 26.1%. Its low cost and high efficiency characteristics show great commercialization prospects. − The electron transport layer (ETL) in PSCs can improve the transfer and transport of photogenerated electrons and thus suppress electron recombination between the conductive electrode and the perovskite layer. − In the development of PSCs, the exploration of efficient ETL is still one of the challenging problems.…”

Outstanding Thermal Stability of Perovskite Solar Cells Based on Zn(TFSI)2-Doped Spiro-MeOTAD

“…After achieving a competitive PCE, there has been reasonable concern about the stability issue of PSCs to take a step toward commercialization. Regarding the perovskite layer, mixed cation- and halide-based compositions have been explored to mitigate crystalline phase instability of formamidinium lead iodide (FAPbI 3 ) coupled with the surface passivation by bulky ammonium cations . The passivation by employing bulky organic ammonium salt between perovskite layer and hole transport layer (HTL) serves as an internal barrier by forming a layered (2D) perovskite layer or an interlayer to block exterior species and migrated ions under various stresses such as light, humidity, bias voltage, and heat.…”