Welcome to Devices and Interfaces Lab

About The Devices and Interfaces Lab

The last few years have seen organic-inorganic perovskite solar cells transcend above the 25% efficiency mark at an astonishingly rapid pace, a feat that has eluded most previous photovoltaic technologies.

At the Device and Interfaces Lab we are interested in understanding the Physics of the Device Reliability and Material Chemistry leading to emerging technological feet in the large area flexible solar cells. We adopt different thin film deposition and device characterization methods to contribute scientifically and technologically towards the development. Details of the work can be found here and the facilities are listed here. We will be happy to extend our facilities to you, if requested.

Our Research

Our research at DIL follows a two way analysis-design mechanism, where we try to fundamentally analyse the systems that we study using computational tools and then use the information thus obtained in the design of better systems.

The research at DIL can be summarized as follows:

The last few years have seen organic-inorganic perovskite solar cells transcend above the 25% efficiency mark at an astonishingly rapid pace, a feat that has eluded most previous photovoltaic technologies. Highly efficient devices based on Methyl Ammonium Lead Halides (MAPbX3) in meso-structured as well as planar device architecture have been reported periodically and such progress can be attributed towards the high absorption coefficient, excellent crystalline nature and longer lifetimes of the charge carriers in the material system.

In addition, the versatility of the material in terms of fabrication techniques and the ability to engineer better quality material in terms of morphology and with reduced defect density has made these systems comparable to existing inorganic thin film photovoltaic materials. Though Methyl Ammonium Lead halides marked the inception of such highly efficient perovskite photovoltaic technology, the incorporation of Formamidinium cations (FAPbX3) have ensured the continuous progress of the technology resulting in 23.7% efficient devices.

Earlier reports have also shown that by varying the halide composition of the material from tri-iodides (MAPbI3) to tri-bromides (MAPbBr3), the band gap of the material can be tuned between 1.55eV and 2.3eV. Such control over the band-gap of the material can greatly help in the optimization of multi-junction tandem solar cells and can also have a huge potential in building integrated photovoltaic applications.

Atomic layer deposition (ALD) is a thin film deposition technique that is based on the sequential use of a gas phase chemical reactions. It is a self-limiting (the amount of film material deposited in each reaction cycle is constant), sequential surface chemistry that deposits conformal thin-films of materials onto substrates of varying compositions.

ALD is similar in chemistry to chemical vapour deposition (CVD), except that the ALD reaction breaks the CVD reaction into two half-reactions, keeping the precursor materials separate during the reaction. Due to the characteristics of self-limiting surface reactions, ALD film growth makes atomic scale deposition control possible.

By keeping the precursors separate throughout the coating process, atomic layer control of film growth can be obtained as fine as ~0.01nm (10pm) per cycle. Separation of the precursors is accomplished by pulsing a purge gas (typically nitrogen or argon) after each precursor pulse to remove excess precursor from the process chamber and prevent 'parasitic' CVD deposition on the substrate.

Development of transparent multi-cation oxy-sulfide thin films by ALD

In this project, we want to develop transparent oxide and oxy-sulfide materials with varied and tunable electronic properties. We use two parallel techniques for the thin film deposition, (i) Atomic Layer Deposition and (ii) Novel Plasma induced Combustion methods.

Development of Large Area Perovskite Solar Cells by Roll-to-Roll technique

Here large area flexible solar cells are in the process of development. A unique combination of solution coordination chemistry is in use to develop the precursor that is applied by two methods; slot-die and blade coating. The established understandings will be used further in R2R deposition setup for flexible perovskite solar cells. We have incurred a state-of-the-art facility for this work.

Understanding the Charge Transport in Perovskite Devices

Charge transport in this mixed electronic-ionic material is interesting. Proper understanding is sought to apprehend the large V OC in the perovskite devices. We employ temperature- dependent (10-350K) measurement of capacitance and impedance spectroscopy and transient photo-induced effects to decouple the individual electronic and ionic contribution in the overall electronic property.

Reliability in Perovskite PV devices

The stability of perovskite devices is essential, considering its futuristic on-field application. We are interested in developing unique strategies in device configuration for a higher operational lifetime. A fully programmed series of measurements under different ambient is done to evaluate the device reliability even under a stressed condition.

Schottky Perovskite Solar Cells

The goal of the research is to find out if and to what extent Schottky solar cells can be made from perovskite semiconductors. Perovskite photovoltaic cells are most commonly considered to act as p-i-n cells, although they may operate as p-n cells in certain configurations and preparation conditions. This will choose such suitably doped perovskites and deliberately use them in a Schottky cell configuration. Based on the accomplishment this configuration will also be extended to MIS structures, where an ultrathin insulating layer will be used between the perovskite and the metallic Schottky contact.

Understanding the Catalytic processes in Atomic Layer Deposition

Considering both the positive and the unseen sides, we are working to develop a unified scenario to sketch a generalized working model supported by adequate experiments to find a landscape of material and method relationship. Our working hypothesis primarily centres on understanding the relationship between the nucleophilic centre of the catalyst and the electrophilic metal centre and establishing a generalized formalism that can predict the reaction feasibility and the deposition mechanism. A combination of DFT calculation (in collaboration with the group of Prof Ankan Paul, IACS) and experimental understanding is the essence of this work.

Aspiring students can contact us for details.

Government Sponsored Projects

Setting up custom made Atomic Layer Deposition facility for various energy related applications(2010-12)

      Industrial Research and Consultancy Centre, IIT Bombay Start-Up fund

In this project, we developed a customized ALD facility with in-situ QCM at IITB. The development includes designing the hardware, control electronics, and software interface. This facility is a landmark one, and based on the learning, we have created many such reactors and later transferred the technology to an Indian company for commercial manufacturing.

Deposition of Multilayer Quantum Well Structures of Metal Chalcogenides by ALD(2011-14)  

      Board of Research in Nuclear Sciences, Department of Atomic Energy, Young Scientist Research Award

Through this project, we have learned to deposit quantum well structures of inorganic materials, and later we improvised it to deposit organic-inorganic heterostructure, applicable in many applications like Li-ion Battery.

Development of Semiconductor Sensitized Solar Cells(2010-15) 

      Ministry of New and Renewable Energy under NCPRE-Phase 1

It is a sub-project of a relatively big consortium project. We were responsible for developing newer avenue in sensitized solar cells. This work essentially embarked on the field of perovskite solar cells.

Direct Regeneration of the Ultra-Thin Semiconductor Absorber Layer by Electronic Conductors for Solid State Semiconductor Sensitized Solar Cells(2010-13)  

      Department of Science & Technology, Young Scientist Research Award

Here, we established a concept of inverse sensitized solar cell concept using CuSCN nanorods. The device efficiency we achieved is very low, but it was interesting to learn and instituting a new conception.

Development of Solid State Nanocrystalline Semiconductor Sensitized Solar Cells by Inverted Morphology(2011-14)  

      Ministry of Defense

Here we developed extremely thin photo-absorber layers of different material for sensitized solar cell applications.

US-India Consortium for Solar Energy Research Institute for India and the United States (SERIIUS) (www.seriius.org)(2012-17)  

      India-US Science and Technology Forum

As a PI from the IITB, we were mostly responsible for the overall project performance of this India-US binational project. Scientifically, we were responsible for developing perovskite solar cells.

Development of Plasma Assisted Atomic Layer Deposition(2015-17) 

      Industrial Research and Consultancy Centre, IIT Bombay

This is again a developmental project where we developed plasma-assisted ALD system.

High Voltage Hybrid-Perovskite Solar Cells - from Device to Stability(2014-16) 

      Department of Science and Technology under India-Israel Binational Collaboration

In contrast to the other perovskite projects, here we have worked on large-V OC devices employing Br instead of Iodine. Such devices are not meant for high-efficiency applications but some other niche applications where potential is essential and not the power output.

High Efficiency Perovskite Solar Cells(2015-18) 

      Department of Science and Technology under Solar Energy Research Initiative.

In this project, our primary concern was to develop the high efficiency perovskite devices from vacuum processes for better material coverage. We developed a four-effusion cell thermal evaporator to deposit MAPbI 3 absorber layer for the device.

Low cost High Efficiency solution processable Solar Cells: From Cell towards Module(2016-19)  

      Ministry of New and Renewable Energy

This was a flagship project from the group. Here we developed very high-efficiency perovskite solar cells on rigid and flexible substrates. We established techniques to enhance the lifetime of the device by reducing the interfacial double-layer capacitance. For details of the outcome, please contact us.

Industry Sponsored Projects
The output of these projects is the property of the sponsored company and hence details are specifically omitted here.

Low Temperature ALD of SiN and SiO2 using novel Nitrogen Oxygen and Silicon precursors(2010-12)  

Applied Materials Inc.

Atomic layer deposition of SiO2(2019-20) 

Applied Materials Inc.

Deposition of TaN and Ti thin films by thermal ALD(2019-20) 

Applied Materials Inc.

Deposition of Cr2O3 by thermal ALD(2019-20) 

Applied Materials Inc.

Development of Protective Coatings using Atomic Layer Deposition (ALD)

Prof. Shaibal K Sarkar, Department of Energy Science and Engineering, IIT Bombay

Usage of plasma processes like dry etching or cleaning in the semiconductor industries results in irreversible and undesirable damages in the chamber parts. Prolonged exposure of many such ionized inert or oxygen or even halide ions are proven to be corrosive, that demands severe maintenance of the industrial production line or even for the stand-alone systems. Thus, it is well accepted that corrosion resistance or protective coatings against such damages are very critical, and essentially, it is the demand of the time. Technically, two main types of etching mechanisms are involved, namely physical sputtering and chemical sputtering. Etching of the material as a result of momentum transfer from the collision cascade induced by the incident radiation, known as physical etching. While, etching of the material as a result chemical reaction induced by the incident radiation leading to desorption of particles is known as chemical etching. Protective coatings hence should exhibit properties like low corrosion/erosion rate, low chemical reaction rate,

and low particle generation and contaminants as a reaction product of the etching process.

Since different etching processes use different reactive gases and deposition conditions, a wide variety of corrosive resistant coatings are required. Various metal oxide layers have already been used in industries against oxygen-rich environments, while various other compounds like metal halides, metal carbides have also been of interest in targeted chemical environments. Recently, metal oxyhalides have also been of interest as corrosive resistant coatings to meet the broader spectrum of plasma environments. We would hence like to propose to develop a range of protective coatings with high physical and chemical etching resistance in various environments to meet the current need for chamber protection.

One another factor that is essential for the protection of these chamber surfaces involves uniform and pin-hole free coating on high aspect ratio structures replicating the complex geometries of insides of the

process chamber. Atomic Layer Deposition (ALD) is a promising alternative to achieve such conformal coatings on three-dimensional and high aspect ratio structures. ALD is an established tool to deposit thinfilms of various binary and ternary compounds. Various scientific journals and conferences have revealed specific interest in ALD grown compounds as the viable option for protection of chamber walls, targeted against various process conditions. We want to propose the development of such binary and ternary metal compounds as protective coatings using custom-built ALD set-up as per the targeted environment and based on the need of the users.

At IIT Bombay, we are very much associated with developing newer ALD processes, both in thermal and plasma-induced. We have several systems that are equipped with in-situ QCM, FTIR, and Mass spectrometry. Besides, we have capabilities for in- situ resistivity measurements to understand the development of the electrical properties of the materials during its growth.

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EN 704, 7 th Floor, Department of Energy Science and Engineering New DESE Building, YP Road, IIT Bombay, Powai Mumbai, Maharashtra – 400076, INDIA



EN 703-704, 7 th Floor, Department of Energy Science and Engineering New DESE Building, YP Road, IIT Bombay, Powai Mumbai, Maharashtra – 400076, INDIA