Co-PI: | Dr. Sumita Mukhopadhyay, Assistant Professor, Engineering and Science University (BESU), Howrah, Prof. S.K.Datta, Professor, Engineering and Science University (BESU), Howrah, Dr. S. Minhaz Hossain, Assistant Professor, Indian Institute of Engineering Science and Technology (IIEST), Shibpur, Dr. Chirasree Roychaudhuri, Associate Professor, Indian Institute of Engineering Science and Technology (IIEST), Shibpur |
Outcome/Output: | Up gradation of existing and development of new solar cell technologies in the field of silicon based thin film and 3G solar cells:
1. Fully operational laboratory facilities along with clean room have been designed and developed. Work on the Up gradation of single junction-Si solar cells and modules have started in collaboration with HHV PV group at Bangalore. Alloys based on silicon and containing hydrogen, oxygen and fluorine have been fabricated using a radio-frequency plasma enhanced chemical vapour deposition (RF-PECVD) using gas mixture of (SiF4 + H2+ CO2). The growth of both amorphous (a-SiO:F:H) and nanocrystalline (ncSiO:F:H) silicon have been studied. Films have been characterized using conductivity, activation energy, optical bandgap, Raman measurement, high resolution transmission electron microscopy and infrared measurement and atomic force microscopy measurements. It is found that in the developed alloy based material the optical bandgap as well as the activation energy of the dark conductivity is controllable and SiO bonds are formed easily. This material can efficiently be used as back reflector of a single junction solar cell or can be used in the micromorph solar cell as intermediate reflective layer (IRL).
2. Using the developed oxide based p, i n and a-SiO:H buffer layers, small area cells of efficiency (initial) of 9.3% was reached and with 15% light induced degradation the stabilized efficiency 0f 7.8% has been obtained.
3. New type of material like n-uc-Si:O:H and n-uc-SiO:F:H for back reflector in single junction cells and Internal Reflection Layer (IRL) for micromorph solar cell has been developed. The main advantage with this technology is that, it can avoid the ex-situ deposition of ZnO:Al, by using doped µc-SiO:H based material grown in the same reactor and with the same process gases as used for thin-film silicon solar cells.
4. HIT solar cell fabrication process has been started and a 6.8% efficiency has been realized in the first attempt using a n-type single crystal wafer. New FZ grade wafer has been procured and 14-15% efficiency is expected within April 2014.
5. Work has also started for development of back surface light trapping structures for n-i-p a-Si solar cells. Silica nano particles of diameter 300nm have been patterned on glass substrate using nano-sphere lithography. Also, Different morphological ZnO on Gold coated Glass substrate by a simple chemical route.
6. Silica nanoparticles atop the glass substrate have been applied to reduce the reflectivity of incident on superstrate type a-Si solar cells. This has led to a relative increase of about 6.5% in efficiency of such cells from an initial efficiency of about 7%.
7. Graphene colloid has been prepared in the laboratory by an inexpensive chemical method by reducing Graphene oxide. Application of monolayer / a few layer Graphene films on p-type silicon solar cells have increased the absolute efficiency by 1% from an initial efficiency of about 11%.
8. Tapered silicon nanopillars having height ~1.5µm, base diameter of ~500nm, top diameter of ~100nm have been fabricated on crystalline silicon wafers by a metal assisted chemical etching method. These nanostructures will have applications in HIT and 3G solar cell configurations Nano-crystalline silicon has been prepared by mechanical milling of crystalline Si by Planetary ball mill followed by successive oxidation and dissolution of the oxidation product. Almost spherical silicon nanocrystalline core of the order of 2- 5 nm surrounded by a silicon oxide shell has been obtained.
Design and development SPV Systems
1. Supercapacitor based Turbo Charger for Mobile Phones for Rural Applications have been designed and developed. Interfacing of supercapacitor with battery of the mobile with a boost converter and due to fast charging characteristics of supercapacitors, the mobile phones can be charged at high current within a few minutes and then can be carried along so that mobile battery can be charged later on during the time of travel. The turbo charger can be charged from SPV or ac power source and has a ‘run time’ of about 20-25 minutes.
2. Significant improvements have been made over existing solar lanterns for their (a) Optical Performance (b) Electrical performance of the lantern and (c) Electrical performance of the charging station. This has led to uniform distribution of the light output and enhancement of the efficiency of existing lantern conditioning unit from 75% to 85%.
3. A cost effective and versatile Data-logging system has been designed for monitoring each BOS component and also Solar PV. The logged data is displayed on Graphical LCD as well as stored into Secure Digital (SD) memory card for further analysis. The system is also capable of monitoring data remotely using GPRS & GSM technology.
4. Weighted efficiency of a charge controller efficiency to charge a lead acid battery bank in a solar off grid system in varying weather conditions e.g. ambient temperature & solar insolation and different state of charges (SOC) of the battery has been performed using a array simulator.
5. FPGA based single phase grid connected (transformer less) 1 kw inverter for solar photo voltaic system has been designed. The key functions of this inverter are maximum power point tracking (MPPT), inversion, grid synchronization and disconnection, safety and protection, facilitation for remote monitoring. |