DESIGN AND DEVELOPMENT

Indian Nano electronics Users Program (INUP) is an initiative to create and spread the expertise of Nano electronics in India, jointly run by the Centre of Excellence in Nano electronics at the Indian Institute of Technology, Bombay (IITB) and Indian Institute of Science, Bangalore (IISc), with financial support from the Department of Information Technology (DIT), the Ministry of Communication and Information Technology (MCIT), Government of India.

The project work of “Design and Development of a Highly Efficient Graphene Based Photovoltaic Device” was shortlisted under Indian Nano electronics Users Programme (INUP) of IIT Bombay. Mr. Sumit Kumar, Assistant Professor, ECE Department, Dronacharya College of Engineering, Gurgaon visited IIT Bombay from 21st September to 2nd October 2015 to execute his work as a Principle Investigator (PI). This project is sanctioned for fourteen months from September 15 to November 16 at INUP IIT Bombay.

About the project:

As graphene is known for its highest electron and hole mobility at room temperature with an optical transmittance of 97.7 % and quantum dots (QDs) due to the impact ionization effect, it is possible to utilize hot electrons in QDs to generate multiple electron-hole pairs per photon. Main focus on assembling solar cells by incorporating the unique properties of graphene - QDs that take advantages of fast electron transfer across large interfacial areas, the ability to tune the absorption spectrum to increase overlap with the solar spectrum and possibility to generate multiple carriers per photon absorbed. This has the potential to result in solar cells that surpass the current efficiency limit for crystalline silicon solar cells by tuning various important parameters. Research mainly focuses to tune the properties of graphene based QDs that could lead to impressive solar cell efficiency with lower potential production cost to produce lightweight hybrid solar cells. This will make these cells viable even in climates perceived as impractical as well as make it possible for the technology to be used on flexible plastics. The graphene based quantum dots synthesized by hot injection techniques at low temperature can be employed in hybrid organic (MEH-PPV, P3HT) composites to evaluate the charge separation mechanism for its potential application in hybrid photovoltaic on rigid (FTO / ITO Glass) & flexible substrates.

Many efforts have been made in this direction; however, there are still many challenges that are yet to be met before its commercialization with economic feasibility. In this regard, work will be carried out for achieving the following targets:

1. Primary focus will be on the synthesis of graphene at large scale with efficient control over its number of layers, which is a pre - requisite condition for many electronic applications

2. Graphene oxide QD (GOQDs) / Graphene QDs (GQDs) owing to its zero bandgap & infinite exciton Bohr Radii can exhibit size - dependant quantum confinement effects. However, it is difficult to synthesize GQDs of smaller size which limits its application in optoelectronics devices with the aid of chemical route. Synthesizing both mono - dispersed & poly - dispersed GQDs by varying capping ligands, reaction temperature & precursor ratios for its applications in optoelectronic devices

3. The GOQD / GQD thin film deposition on arbitrary substrates will be performed to achieve desired tuneable band-gap

4. Lower synthesis temperature would be employed for the efficient formation of GOQD / GQDs (1500 – 3500 C).

The following steps are carried to execute the work:

1. First step: for the synthesis of graphene oxide using Glutathione from Graphite Flakes

2. Second step: for the synthesis of Colloidal Graphene oxide quantum dots (GOQD) and Graphene quantum Dots (GQD) for high-performance organic solar cells

3. Third Step: As prepared GOQD’s & GQD’s would be characterized by PL for emission, UV-Vis absorbance for size determination, & Dynamic Laser scattering (DLS) would be employed

4. Fourth step: The optimized GOQD’s & GQD’s would then be mixed with TiO2 [10] either by (i) direct adsorption or using a suitable linker (like MPA, TGA & Cystein) and (ii) removing off excess of ligands using proper ligand exchange procedure to promote interaction between TiO2 and GOQD’s & GQD’s

5. Fifth Step: Above prepared hybrid organic – inorganic composites would be characterize using various techniques like XRD, TEM, HRTEM, XPS, FTIR Photoluminescence

6. Sixth Step: I-V characteristics of the above hybrid organic – inorganic composites would be done to obtain the maximum photocurrent conversion efficiency.

The project work served as a platform for the researchers in Nanoelectronics to come together and benefit from complementary expertise.