Anurag Krishna

Optoelectronic or photovoltaic device with metal halide perovskite film treated by passivating agent

Michael Graetzel, Anurag Krishna, Lukas Pfeifer, Shaik Mohammed Zakeeruddin

This invention relates to an optoelectronic or photovoltaic device comprising a perovskite or metal halide perovskite film treated by one or more compounds of formula (I): ((R1-NH(R2)-R3)+)nW (I), wherein n is an integer selected from 1, 2, or 3; R1, R2, R3 are independently selected from a hydrocarbyl group containing 1-40 carbon atoms said hydrocarbyl group, if said hydrocarbyl group comprises 3 or more carbons, may be linear or branched; and W is an anion.

2023

A universal co-solvent dilution strategy enables facile and cost-effective fabrication of perovskite photovoltaics

Paramvir Ahlawat, Masaud Hassan S Almalki, Viacheslav Bolnykh, Ulf Anders Hagfeldt, Anurag Krishna, Linfeng Pan, Dan Ren, Ursula Röthlisberger, Sandy Sanchez Alonso, Tzu-Sen Su, Narges Yaghoobi Nia, Shaik Mohammed Zakeeruddin, Hong Zhang

Cost management and toxic waste generation are two key issues that must be addressed before the commercialization of perovskite optoelectronic devices. We report a ground-breaking strategy for eco-friendly and cost-effective fabrication of highly efficient perovskitesolar cells. This strategy involves the usage of a high volatility co-solvent, which dilutesperovskite precursors to a lower concentration (1.4 M) solution. More than 70% of toxicwaste and material cost can be reduced. Mechanistic insights reveal ultra-rapid evaporationof the co-solvent together with beneficial alteration of the precursor colloidal chemistryupon dilution with co-solvent, which in-situ studies and theoretical simulations confirm.The co-solvent tuned precursor colloidal properties also contribute to the enhancement ofthe stability of precursor solution, which extends its processing window thus minimizing thewaste. This strategy is universally successful across different perovskite compositions, andscales from small devices to large-scale modules using industrial spin-coating, potentiallyeasing the lab-to-fab translation of perovskite technologies.

2022

Formation of High-Performance Multi-Cation Halide Perovskites Photovoltaics by delta-CsPbI3/delta-RbPbI3 Seed-Assisted Heterogeneous Nucleation

Essa Awadh R Alharbi, Masaud Hassan S Almalki, Thomas Paul Baumeler, Felix Thomas Eickemeyer, Ulf Anders Hagfeldt, Anurag Krishna, Mounir Driss Mensi, Olivier Ouellette, Linfeng Pan, Zaiwei Wang, Bowen Yang, Shaik Mohammed Zakeeruddin

The performance of perovskite solar cells is highly dependent on the fabrication method; thus, controlling the growth mechanism of perovskite crystals is a promising way towards increasing their efficiency and stability. Herein, a multi-cation halide composition of perovskite solar cells is engineered via the two-step sequential deposition method. Strikingly, it is found that adding mixtures of 1D polymorphs of orthorhombic delta-RbPbI3 and delta-CsPbI3 to the PbI2 precursor solution induces the formation of porous mesostructured hexagonal films. This porosity greatly facilitates the heterogeneous nucleation and the penetration of FA (formamidinium)/MA (methylammonium) cations within the PbI2 film. Thus, the subsequent conversion of PbI2 into the desired multication cubic alpha-structure by exposing it to a solution of formamidinium methylammonium halides is greatly enhanced. During the conversion step, the delta-CsPbI3 also is fully integrated into the 3D mixed cation perovskite lattice, which exhibits high crystallinity and superior optoelectronic properties. The champion device shows a power conversion efficiency (PCE) over 22%. Furthermore, these devices exhibit enhanced operational stability, with the best device retaining more than 90% of its initial value of PCE under 1 Sun illumination with maximum power point tracking for 400 h.

WILEY-V C H VERLAG GMBH2021

Methylammonium Triiodide for Defect Engineering of High-Efficiency Perovskite Solar Cells

Paramvir Ahlawat, Essa Awadh R Alharbi, Claudia Esther Avalos, Thomas Paul Baumeler, Mathias Dankl, Felix Thomas Eickemeyer, George Cameron Fish, Michael Graetzel, Ulf Anders Hagfeldt, Elsa John, Anurag Krishna, Mounir Driss Mensi, Jacques-Edouard Moser, Olivier Ouellette, Linfeng Pan, Lukas Pfeifer, Ursula Röthlisberger, Pascal Alexander Schouwink, Viktor Skorjanc, Bowen Yang, Shaik Mohammed Zakeeruddin

The defects present in metal halide perovskite are deleterious to both the performance and stability of photovoltaic devices. Consequently, there is an intense focus on developing defect mitigation strategies. Herein we report a facile strategy that employs methylammonium triiodide (MAI3) as an additive to the perovskite precursor solution. We examine the effect of MAI3 on the structural and optoelectronic properties by X-ray diffraction, density functional theory calculations, molecular dynamics simulations, solid-state nuclear magnetic resonance, steady-state, time-resolved photoluminescence (TRPL), and time-resolved terahertz spectroscopy (TRTS). Specifically, TRPL and TRTS show that MAI3 suppresses nonradiative recombination and increases the charge carrier mobility. As a result, the champion device shows a power conversion efficiency (PCE) of 23.46% with a high fill factor of >80%. Furthermore, these devices exhibit enhanced operational stability, with the best device retaining ∼90% of its initial PCE under 1 sun illumination with maximum power point tracking for 350 h.

2021

Multimodal host–guest complexation for efficient and stable perovskite photovoltaics

Paramvir Ahlawat, Zhaowen Dong, Felix Thomas Eickemeyer, David Lyndon Emsley, Michael Graetzel, Jinming Guo, Ulf Anders Hagfeldt, Michael Allan Hope, Farzaneh Jahanbakhshi, Anurag Krishna, Jovana Milic, Aditya Mishra, Marko Mladenovic, Olivier Ouellette, Dan Ren, Ursula Röthlisberger, Tzu-Sen Su, Zaiwei Wang, Shaik Mohammed Zakeeruddin, Hong Zhang, Zhiwen Zhou

Formamidinium lead iodide perovskites are promising light-harvesting materials, yet stabilizing them under operating conditions without compromising optimal optoelectronic properties remains challenging. We report a multimodal host–guest complexation strategy to overcome this challenge using a crown ether, dibenzo-21-crown-7, which acts as a vehicle that assembles at the interface and delivers Cs+ ions into the interior while modulating the material. This provides a local gradient of doping at the nanoscale that assists in photoinduced charge separation while passivating surface and bulk defects, stabilizing the perovskite phase through a synergistic effect of the host, guest, and host–guest complex. The resulting solar cells show power conversion efficiencies exceeding 24% and enhanced operational stability, maintaining over 95% of their performance without encapsulation for 500 h under continuous operation. Moreover, the host contributes to binding lead ions, reducing their environmental impact. This supramolecular strategy illustrates the broad implications of host–guest chemistry in photovoltaics.

2021

Compositional and Interface Engineering of Organic-Inorganic Lead Halide Perovskite Solar Cells

Ulf Anders Hagfeldt, Anurag Krishna, Haizhou Lu, Shaik Mohammed Zakeeruddin

Power conversion efficiency (PCE) of the perovskite solar cells (PSCs) has remarkably been increased from3.1%to 25.2%. The fast expansion of the PSCs has been along with the development of compositional and interface engineering, which has been playing a critical role. For the PSCs with record high-efficiency and stability, the perovskite absorber layer has been changed fromthe initialMAPbI3- to FAPbI3-based compositions. Owing to the enormous engineering works, perovskite absorber layers with monolithic grains could be achieved, in which the interior defects are negligible compared with the surface defects. Therefore, interface engineering, which can passivate the surface defects and/or isolate the perovskite from the environmental moistures, has been playing a more and more important role to further boost the PCE and stability of the PSCs. Herein, a compact review study of the compositional and interface engineering is presented and promising strategies and directions of the PSCs are discussed.

2020

Defect Passivation via the Incorporation of Tetrapropylammonium Cation Leading to Stability Enhancement in Lead Halide Perovskite

Anurag Krishna

Improving the performances of photovoltaic (PV) devices by suppressing nonradiative energy losses through surface defect passivation and enhancing the stability to the level of standard PV represents one critical challenge for perovskite solar cells. Here, reported are the advantages of introducing a tetrapropylammonium (TPA(+)) cation that combines two key functionalities, namely surface passivation of CH3NH3PbI3 nanocrystals through strong ionic interaction with the surface and bulk passivation via formation of a type I heterostructure that acts as a recombination barrier. As a result, nonencapsulated perovskite devices with only 2 mol% of TPA(+) achieve power conversion efficiencies over 18.5% with higher V-OC under air mass 1.5G conditions. The devices fabricated retain more than 85% of their initial performances for over 1500 h under ambient conditions (55% RH +/- 5%). Furthermore, devices with TPA(+) also exhibit excellent operational stability by retaining over 85% of the initial performance after 250 h at maximum power point under 1 sun illumination. The effect of incorporation of TPA(+) on the structural and optoelectronic properties is studied by X-ray diffraction, ultraviolet-visible absorption spectroscopy, ultraviolet photon-electron spectroscopy, time-resolved photoluminescence, and scanning electron microscopy imaging. Atomic-level passivation upon addition of TPA(+) is elucidated employing 2D solid-state NMR spectroscopy.

WILEY-V C H VERLAG GMBH2020

Mixed Dimensional 2D/3D Hybrid Perovskite Absorbers: The Future of Perovskite Solar Cells?

Anurag Krishna, Mohammad Khaja Nazeeruddin

The cost-effective processability and high efficiency of the organic-inorganic metal halide perovskite solar cells (PSCs) have shown tremendous potential to intervene positively in the generation of clean energy. However, prior to an industrial scale-up process, there are certain critical issues such as the lack of stability against over moisture, light, and heat, which have to be resolved. One of the several proposed strategies to improve the stability that has lately emerged is the development of lower-dimensional (2D) perovskite structures derived from the Ruddlesden-Popper (RP) phases. The excellent stability under ambient conditions shown by 2D RP phase perovskites has made the scalability expectations burgeon since it is one of the most credible paths toward stable PSCs. In this review, the 2D/3D mixed system for photovoltaics (PVs) is elaborately discussed with the focus on the crystal structure, optoelectronic properties, charge carrier dynamics, and their impact on the photovoltaic performances. Finally, some of the further challenges are highlighted while outlining the perspectives of 2D/3D perovskites for high-efficiency stable solar cells.

WILEY-V C H VERLAG GMBH2019