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Min H, Hu J, Xu Z, Liu T, Khan SUZ, Roh K, Loo YL, Rand BP. Hot-Casting-Assisted Liquid Additive Engineering for Efficient and Stable Perovskite Solar Cells. Adv Mater 2022; 34:e2205309. [PMID: 35841176 DOI: 10.1002/adma.202205309] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Revised: 07/12/2022] [Indexed: 06/15/2023]
Abstract
High-performance inorganic-organic lead halide perovskite solar cells (PSCs) are often fabricated with a liquid additive such as dimethyl sulfoxide (DMSO), which retards crystallization and reduces roughness and pinholes in the perovskite layers. However, DMSO can be trapped during perovskite film formation and induce voids and undesired reaction byproducts upon later processing steps. Here, it is shown that the amount of residual DMSO can be reduced in as-spin-coated films significantly through use of preheated substrates, or a so-called hot-casting method. Hot casting increases the perovskite film thickness given the same concentration of solutions, which allows for reducing the perovskite solution concentration. By reducing the amount of DMSO in proportion to the concentration of perovskite precursors and using hot casting, it is possible to fabricate perovskite layers with improved perovskite-substrate interfaces by suppressing the formation of byproducts, which increase trap density and accelerate degradation of the perovskite layers. The best-performing PSCs exhibit a power conversion efficiency (PCE) of 23.4% (23.0% stabilized efficiency) under simulated solar illumination. Furthermore, encapsulated devices show considerably reduced post-burn-in decay, retaining 75% and 90% of their initial and post-burn-in efficiencies after 3000 h of operation with maximum power point tracking (MPPT) under high power of ultraviolet (UV)-containing continuous light exposure.
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Affiliation(s)
- Hanul Min
- Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, 08544, USA
- Princeton Institute for International and Regional Studies, Princeton University, Princeton, NJ, 08544, USA
| | - Junnan Hu
- Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Zhaojian Xu
- Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Tianran Liu
- Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Saeed-Uz-Zaman Khan
- Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Kwangdong Roh
- Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Yueh-Lin Loo
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Barry P Rand
- Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ, 08544, USA
- Andlinger Center for Energy and the Environment, Princeton University, Princeton, NJ, 08544, USA
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Abstract
Enhanced delocalization is beneficial for absorbing molecules in organic solar cells, and in particular bilayer devices, where excitons face small diffusion lengths as a barrier to reaching the charge-generating donor-acceptor interface. As hybrid light-matter states, polaritons offer exceptional delocalization which could be used to improve the efficiency of bilayer organic photovoltaics. Polariton delocalization can aid in delivering excitons to the donor-acceptor interface, but the subsequent charge transfer event must compete with the fast decay of the polariton. To evaluate the viability of polaritons as tools to improve bilayer organic solar cells, we studied the decay of the lower polariton in three cavity systems: a donor only, a donor-acceptor bilayer, and a donor-acceptor blend. Using several spectroscopic techniques, we identified an additional decay pathway through charge transfer for the polariton in the bilayer cavity, demonstrating charge transfer from the polariton is fast enough to outcompete the decay to the ground state.
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Affiliation(s)
- Courtney A DelPo
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Saeed-Uz-Zaman Khan
- Department of Electrical and Computer Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Kyu Hyung Park
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Bryan Kudisch
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Barry P Rand
- Department of Electrical and Computer Engineering, Princeton University, Princeton, New Jersey 08544, United States
- Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey 08544, United States
| | - Gregory D Scholes
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Schwarz KN, Mitchell VD, Khan SUZ, Lee C, Reinhold A, Smith TA, Ghiggino KP, Jones DJ, Rand BP, Scholes GD. Morphological Requirements for Nanoscale Electric Field Buildup in a Bulk Heterojunction Solar Cell. J Phys Chem Lett 2021; 12:537-545. [PMID: 33378206 DOI: 10.1021/acs.jpclett.0c03425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The morphology of organic semiconductors is critical to their function in optoelectronic devices and is particularly crucial in the donor-acceptor mixture that comprises the bulk heterojunction of organic solar cells. Here, energy landscapes can play integral roles in charge photogeneration, and recently have been shown to drive the accumulation of charge carriers away from the interface, resulting in the buildup of large nanoscale electric fields, much like a capacitor. In this work we combine morphological and spectroscopic data to outline the requirements for this interdomain charge accumulation, finding that this effect is driven by a three-phase morphology that creates an energetic cascade for charge carriers. By adjusting annealing conditions, we show that domain purity, but not size, is critical for an electro-absorption feature to grow-in. This demonstrates that the energy landscape around the interface shapes the movement of charges and that pure domains are required for charge carrier buildup that results in reduced recombination and large interdomain nanoscale electric fields.
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Affiliation(s)
- Kyra N Schwarz
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Valerie D Mitchell
- Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168, Australia
| | | | | | - Adam Reinhold
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | | | | | | | | | - Gregory D Scholes
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Londi G, Khan SUZ, Muccioli L, D'Avino G, Rand BP, Beljonne D. Fate of Low-Lying Charge-Transfer Excited States in a Donor:Acceptor Blend with a Large Energy Offset. J Phys Chem Lett 2020; 11:10219-10226. [PMID: 33206537 DOI: 10.1021/acs.jpclett.0c02858] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In an effort to gain a comprehensive picture of the interfacial states in bulk heterojunction solar cells, we provide a combined experimental-theoretical analysis of the energetics and dynamics of low-lying electronic charge-transfer (CT) states in donor:acceptor blends with a large frontier orbital energy offset. By varying the blend composition and temperature, we unravel the static and dynamic contributions to the disordered density of states (DOS) of the CT-state manifold and assess their recombination to the ground state. Namely, we find that static disorder (conformational and electrostatic) shapes the CT DOS and that fast nonradiative recombination crops the low-energy tail of the distribution probed by external quantum efficiency (EQE) measurements (thereby largely contributing to voltage losses). Our results then question the standard practice of extracting microscopic parameters such as exciton energy and energetic disorder from EQE.
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Affiliation(s)
- Giacomo Londi
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000 Mons, Belgium
| | - Saeed-Uz-Zaman Khan
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Luca Muccioli
- Department of Industrial Chemistry, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Gabriele D'Avino
- Grenoble Alpes University, CNRS, Grenoble INP, Institut Néel, 25 rue des Martyrs, 38042 Grenoble, France
| | - Barry P Rand
- Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, United States
- Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey 08544, United States
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000 Mons, Belgium
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DelPo C, Kudisch B, Park KH, Khan SUZ, Fassioli F, Fausti D, Rand BP, Scholes GD. Polariton Transitions in Femtosecond Transient Absorption Studies of Ultrastrong Light-Molecule Coupling. J Phys Chem Lett 2020; 11:2667-2674. [PMID: 32186878 PMCID: PMC8154840 DOI: 10.1021/acs.jpclett.0c00247] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Strong light-matter coupling is emerging as a fascinating way to tune optical properties and modify the photophysics of molecular systems. In this work, we studied a molecular chromophore under strong coupling with the optical mode of a Fabry-Perot cavity resonant to the first electronic absorption band. Using femtosecond pump-probe spectroscopy, we investigated the transient response of the cavity-coupled molecules upon photoexcitation resonant to the upper and lower polaritons. We identified an excited state absorption from upper and lower polaritons to a state at the energy of the second cavity mode. Quantum mechanical calculations of the many-molecule energy structure of cavity polaritons suggest assignment of this state as a two-particle polaritonic state with optically allowed transitions from the upper and lower polaritons. We provide new physical insight into the role of two-particle polaritonic states in explaining transient signatures in hybrid light-matter coupling systems consistent with analogous many-body systems.
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Affiliation(s)
- Courtney
A. DelPo
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Bryan Kudisch
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Kyu Hyung Park
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Saeed-Uz-Zaman Khan
- Department
of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Francesca Fassioli
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- SISSA−
Scuola Internazionale Superiore di Studi Avanzati, Trieste 34136, Italy
| | - Daniele Fausti
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department
of Physics, University of Trieste, Via A. Valerio 2, 34127 Trieste, Italy
- Elettra-Sincrotrone
Trieste S.C.p.A., Strada
Statale 14 - km 163.5 in AREA Science Park, 34149 Basovizza, Trieste, Italy
| | - Barry P. Rand
- Department
of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, United States
- Andlinger
Center for Energy and the Environment, Princeton
University, Princeton, New Jersey 08544, United States
| | - Gregory D. Scholes
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Schwarz KN, Geraghty PB, Mitchell VD, Khan SUZ, Sandberg OJ, Zarrabi N, Kudisch B, Subbiah J, Smith TA, Rand BP, Armin A, Scholes GD, Jones DJ, Ghiggino KP. Reduced Recombination and Capacitor-like Charge Buildup in an Organic Heterojunction. J Am Chem Soc 2020; 142:2562-2571. [PMID: 31922408 DOI: 10.1021/jacs.9b12526] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Organic photovoltaic (OPV) efficiencies continue to rise, raising their prospects for solar energy conversion. However, researchers have long considered how to suppress the loss of free carriers by recombination-poor diffusion and significant Coulombic attraction can cause electrons and holes to encounter each other at interfaces close to where they were photogenerated. Using femtosecond transient spectroscopies, we report the nanosecond grow-in of a large transient Stark effect, caused by nanoscale electric fields of ∼487 kV/cm between photogenerated free carriers in the device active layer. We find that particular morphologies of the active layer lead to an energetic cascade for charge carriers, suppressing pathways to recombination, which is ∼2000 times less than predicted by Langevin theory. This in turn leads to the buildup of electric charge in donor and acceptor domains-away from the interface-resistant to bimolecular recombination. Interestingly, this signal is only experimentally obvious in thick films due to the different scaling of electroabsorption and photoinduced absorption signals in transient absorption spectroscopy. Rather than inhibiting device performance, we show that devices up to 600 nm thick maintain efficiencies of >8% because domains can afford much higher carrier densities. These observations suggest that with particular nanoscale morphologies the bulk heterojunction can go beyond its established role in charge photogeneration and can act as a capacitor, where adjacent free charges are held away from the interface and can be protected from bimolecular recombination.
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Affiliation(s)
| | | | | | | | - Oskar J Sandberg
- Department of Physics , Swansea University , Singleton Park , Swansea , Wales SA2 8PP , United Kingdom
| | - Nasim Zarrabi
- Department of Physics , Swansea University , Singleton Park , Swansea , Wales SA2 8PP , United Kingdom
| | | | | | | | | | - Ardalan Armin
- Department of Physics , Swansea University , Singleton Park , Swansea , Wales SA2 8PP , United Kingdom
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