Interdependence of photon upconversion performance and antisolvent processing in thin-film halide perovskite-sensitized triplet–triplet annihilators

Prashanthan, Karunanantharajah; Naydenov, Boris; Lips, K.; Unger, Eva; MacQueen, Rowan W.

doi:10.1063/5.0026564

Cited by 25 publications

(33 citation statements)

References 40 publications

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“…To‐date, all reported bulk perovskite‐sensitized TTA‐UC devices are fully solution‐processed by either spin‐coating the organic annihilator layer onto the perovskites or directly incorporating the annihilator into the antisolvent, [ 11,12,18–21 ] which poses an obstacle to unravelling the detailed photophysics of perovskite‐sensitized upconversion. Perovskites are notoriously sensitive to solvent exposure and fabrication conditions.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Trap‐Assisted Triplet Generation in Lead Halide Perovskite Sensitized Solid‐State Upconversion

et al. 2021

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Photon upconversion via triplet–triplet annihilation (TTA) has promise for overcoming the Shockley–Queisser limit for single‐junction solar cells by allowing the utilization of sub‐bandgap photons. Recently, bulk perovskites have been employed as sensitizers in solid‐state upconversion devices to circumvent poor exciton diffusion in previous nanocrystal (NC)‐sensitized devices. However, an in‐depth understanding of the underlying photophysics of perovskite‐sensitized triplet generation is still lacking due to the difficulty of precisely controlling interfacial properties of fully solution‐processed devices. In this study, interfacial properties of upconversion devices are adjusted by a mild surface solvent treatment, specifically altering perovskite surface properties without perturbing the bulk perovskite. Thermal evaporation of the annihilator precludes further solvent contamination. Counterintuitively, devices with more interfacial traps show brighter upconversion. Approximately an order of magnitude difference in upconversion brightness is observed across different interfacial solvent treatments. Sequential charge transfer and interfacial trap‐assisted triplet sensitization are demonstrated by comparing upconversion performance, transient photoluminescence dynamics, and magnetic field dependence of the devices. Incomplete triplet conversion from transferred charges and consequent triplet‐charge annihilation (TCA) are also observed. The observations highlight the importance of interfacial control and provide guidance for further design and optimization of upconversion devices using perovskites or other semiconductors as sensitizers.

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Section: Introductionmentioning

confidence: 99%

Interfacial Trap‐Assisted Triplet Generation in Lead Halide Perovskite Sensitized Solid‐State Upconversion

et al. 2021

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“…The same properties which make perovskite materials uniquely qualified as the active layer in a PV, enable triplet sensitization through a freecharge carrier process. [8][9][10][11][12][13][14][15] Photon UC in general describes the process of increasing the emitted photon energy upon photon absorption. [16][17][18][19][20] To comply with energy conservation laws, this process requires the combination of the energy of multiple absorbed photons to generate a single high energy excited state.…”

Section: Introductionmentioning

confidence: 99%

“…25 However, this is counteracted by a higher absorption of the FA-rich perovskites, which we have previously shown to exhibit higher UC photoluminescence (PL) intensities than their MA-rich counterparts. Other important factors to consider are the native PL lifetimes and resulting carrier diffusion lengths, 14 Fermi levels 24 and interfacial band bending, 11,26 which can all influence the number of charges extracted at the perovskite/rubrene interface. We have previously shown that one of the current limitations of the perovskite/rubrene UC system is incomplete charge extraction, which can be attributed to the lack of driving force for electron transfer, a limited driving force for charge transport to the interface, localized trap states or charge transfer states mediating the charge transfer.…”

Section: Introductionmentioning

confidence: 99%

Mixed halide bulk perovskite triplet sensitizers: Interplay between band alignment, mid-gap traps, and phonons

Bieber

VanOrman

Drozdick

et al. 2021

The Journal of Chemical Physics

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Photon upconversion, particularly via triplet-triplet annihilation (TTA), could prove beneficial in expanding the efficiencies and overall impacts of optoelectronic devices across a multitude of technologies. The recent development of bulk metal halide perovskites as triplet sensitizers is one potential step toward the industrialization of upconversion-enabled devices. Here, we investigate the impact of varying additions of bromide into a lead iodide perovskite thin film on the TTA upconversion process in the annihilator molecule rubrene. We find an interplay between the bromide content and the overall device efficiency. In particular, a higher bromide content results in higher internal upconversion efficiencies, enabled by more efficient charge extraction at the interface, likely due to a more favorable band alignment. However, the external upconversion efficiency decreases, as the absorption cross section in the near infrared is reduced. The highest upconversion performance is found in our study for a bromide content of 5%. This result can be traced back to a high absorption cross section in the near infrared and higher photoluminescence quantum yield in comparison to the iodide-only perovskite, as well as an increased driving force for charge transfer.

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“…However, to date, the exact mechanism of triplet sensitization is still unclear. [30][31][32][33] Understanding the fundamental mechanism of triplet sensitization at the perovskite/organic interface will be the key in further improving perovskite-based UC, as it will unlock engineering pathways to further increase the device performance.…”

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confidence: 99%

“…Particularly, it emphasizes that only a small fraction of free charges created upon photoexcitation are successfully extracted and return upconverted photons despite the long-lived nature of the free carriers in the perovskite, which should allow a large number of charges to be extracted within their lifetime. 23,28 Possible causes include localized states mediating electron and hole transfer and limiting the number of generated triplet states 30,31 and short-lived transient states (e.g. hot carriers) being involved in the triplet generation process.…”

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confidence: 99%

Ultrafast Triplet Generation at the Lead Halide Perovskite/Rubrene Interface

Conti

Bieber

VanOrman

et al. 2021

Preprint

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Triplet sensitization of rubrene by bulk lead halide perovskites has recently resulted in efficient infrared-to-visible photon upconversion via triplet-triplet annihilation. Notably, this process occurrs under solar relavant fluxes, potentially paving the way toward integration with photovoltaic devices. In order to further improve the upconversion efficiency, the fundamental photophysical pathways at the perovskite/rubrene interface must be clearly understood to maximize charge extraction. Here, we utilize ultrafast transient absorption spectroscopy to elucidate the processes underlying the triplet generation at the perovskite/rubrene interface. Based on the bleach and photoinduced absorption features of the perovskite and perovskite/rubrene devices obtained at multiple pump wavelengths and fluences, along with their resultant kinetics, our results do not support charge transfer states or long-lived trap states as the underlying mechanism. Instead, the data points towards a triplet sensitization mechanism based on rapid extraction of thermally excited carriers on the picosecond timescale.

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Interdependence of photon upconversion performance and antisolvent processing in thin-film halide perovskite-sensitized triplet–triplet annihilators

Abstract: Note: This paper is part of the JCP Special Topic on Up-and Down-Conversion in Molecules and Materials.

Cited by 25 publications

References 40 publications

Interfacial Trap‐Assisted Triplet Generation in Lead Halide Perovskite Sensitized Solid‐State Upconversion

Interfacial Trap‐Assisted Triplet Generation in Lead Halide Perovskite Sensitized Solid‐State Upconversion

Mixed halide bulk perovskite triplet sensitizers: Interplay between band alignment, mid-gap traps, and phonons

Ultrafast Triplet Generation at the Lead Halide Perovskite/Rubrene Interface

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