The charge-carrier lifetime in halide perovskites often varies by orders of magnitude with the injection level, complicating the analysis of conventional time-resolved photoluminescence and comparisons of reported lifetimes. We use intensity-modulated photoluminescence spectroscopy (IMPLS) as a frequency-domain alternative. Carried out under operating conditions, it yields the lifetime at a specific injection level, e.g., one-sun-equivalent illumination. On thin films, IMPLS and steady-state photoluminescence yield comparable lifetimes. For perovskite/transport-layer stacks, the IMPLS response becomes more complex. A dedicated transfer function disentangles charge transfer from interface recombination and predicts an upper limit on the charge-carrier lifetime in the solar cell. In devices, electrical methods such as intensity-modulated photovoltage spectroscopy (IMVS) often fail to measure the lifetime due to capacitive effects. IMPLS shows not only the same two characteristic frequencies as IMVS, but also a third one, thereby resolving the lifetime itself.
Methylammonium/bromide‐free perovskite solar cells (PSCs) with mixed A‐site cations of varying ionic radii often suffer from uncontrolled crystallization and a restricted spectral response, limiting further improvements in both power conversion efficiency (PCE) and stability. Herein, π‐conjugated terpyridine‐zinc(II) (ZnTPY) coordination nanosheets (CONASHs) are introduced as multifunctional additives for heterogeneous nucleation and down‐conversion, offering a versatile platform that simultaneously promotes the crystal quality of triple‐cation formamidinium/cesium/rubidium lead iodide perovskites and improves short‐wavelength photon utilization. Synthesized via bottom‐up liquid‐liquid interfacial coordination, ZnTPY CONASHs can be ultrasonically fragmented into pieces enriched with unsaturated terpyridine moieties, which form multidentate chelates with PbI 2 to generate ZnTPY‐[PbI 6‐x ] 4− octahedral heteronuclei. These adducts promote low‐barrier heterogeneous nucleation in perovskites, which synergistically suppresses defect densities and prolongs photocarrier lifetimes, thereby enhancing both crystallinity and environmental stability. In parallel, the intramolecular charge‐transfer absorption and subsequent visible emission of CONASHs facilitate down‐conversion, which augments the external quantum efficiency in the 300–590 nm range and optimizes ultraviolet light harvesting in the ZnTPY‐modified perovskites. Consequently, the PSCs with ZnTPY additive achieve a champion PCE of 22.50%, compared to 20.94% for the control, along with improved outdoor stability. These findings highlight the substantial practical potential of the CONASH‐induced strategy for future PSC applications.
Self‐assembled hole transport monolayers (SAMs) have become indispensable components of high‐performance inverted perovskite solar cells (PSCs). SAMs not only govern the interfacial hole extraction kinetics but also influence the crystallization quality of the overlying perovskite film and the properties of the buried interface. In this work, we designed and synthesized a novel SAM featuring a terminal dibenzothiophene group, designated DBT‐4PACz. Our investigation reveals that, compared with the commercial benchmark Me‐4PACz, DBT‐4PACz forms denser and more uniform coverage on the substrate, exhibits higher conductivity, and demonstrates a more favorable energy level alignment with the perovskite. Moreover, the thiophene moiety in DBT‐4PACz enhances the interaction with the perovskite. This, combined with the denser SAM layer, improves the crystallization quality of the perovskite and reduces interfacial defects. Leveraging this molecular design, inverted PSCs employing DBT‐4PACz achieved a remarkable power conversion efficiency of 27.01% (certified 26.62%), significantly surpassing the performance of Me‐4PACz‐based control devices (26.16%). Furthermore, DBT‐4PACz‐based devices exhibit superior operational stability.
Self‐assembled monolayers (SAMs) play an important role in high‐efficiency inverted perovskite solar cells (PSCs), which optimize interfacial contact and facilitate efficient hole extraction. Conventional SAMs adopt flexible alkyl chains as linkers, which may suffer from loose molecular arrangement, unfavorable surface coverage, and poor interfacial stability, limiting the overall device performance. Although SAMs incorporating rigid linkers have recently been reported, their molecular structures are mostly confined to phenyl‐based linkers. In this work, a rigid furan linker was introduced for the first time to construct new SAMs, and we investigated how anchoring‐group substitution positions affect device performance. Results showed that the rigid furan linker effectively enabled a uniform and dense coverage on the substrate. Moreover, TA2 with a carboxylic acid at C5 position possesses a larger dipole moment than TA1, which could more effectively modulate the substrate work function, facilitate interfacial charge transport, and suppress nonradiative recombination. Inverted PSCs based on TA2 achieved an optimized efficiency of 25.34%. Additionally, large‐area devices (1 cm 2 ) and modules (15.136 cm 2 ) delivered efficiencies of 23.3% and 22.99%, respectively. This work suggests that furan could work well as the linker to connect the terminal group and the anchoring unit, establishing an effective molecular design guideline for high‐performance SAMs.