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Kerrie Morris

Cohort 5

246

Kerrie Morris completed her MChem in Chemistry at the University of Lincoln researching dynamic covalent bonding of phenylboronic acid under humidity controlled conditions for her final year project and crystal engineering of co-crystals using a cation chaperone for her third year project. She developed a keen interest in fine tuning molecular structures and understanding the interactions which gave rise to the material properties. She also studied photovoltaic devices during her third year and was intrigued by current research so combining and developing knowledge in these fields was an ideal opportunity and she will be undertaking her PhD at Loughborough University investigating doping strategies for next generation CdTe solar cells. She also has a passion for growing her own fruit and vegetables, taking part in local horticultural shows and providing fresh organic food for her family.



Project

Doping strategies for next generation CdTe solar cells

Over the last 6 years, CdTe photovoltaics (PV) have enjoyed a steady performance improvement after remaining relatively stagnant for the previous 10 years. These improvements have largely been pushed by one company, First Solar Inc, who have successfully commercialised the technology to become the largest thin film PV manufacturer in the world. This steady efficiency increase has come about from, in the first instance, focusing on increasing photon absorption to improve current collection. Whilst improving the current collection in these devices has yielded higher and higher efficiencies, it is important to address the voltage loss which CdTe devices currently suffer from. Only then will CdTe PV fully realise its potential. Currently, CdTe suffers from a significant voltage deficit, which prevents devices from exceeding 900mV open circuit voltage. This voltage deficit has been attributed to two phenomena: a) Low doping density of around 1014/cm3and b) low minority carrier lifetime (typically less than 5ns). Simultaneously improving both will lead to improved open circuit voltages. Strategies to improve doping in CdTe include using group V dopants, such as phosphorus, will be investigated in this project to improve doping levels in CdTe thin films from 1014 to 1016/cm3, which are typical in high efficiency CIGS solar cells. In addition to group V doping, selenium alloying will also be explored in this project. There is growing evidence that alloying CdTe with Se (to form CdTexSe1-x) can significantly improve the minority carrier lifetime of the film without resorting to exotic growth methods. In addition to this, alloying CdTe with Se also represents a unique opportunity to grade the band gap of the film, which has been successfully used in CIGS PV to promote a back surface field, which promotes collection of electrons generated near the back of the device. This is particularly important in materials which have high doping density. The investigation of the CdTexSe1-x material as well as group V doping represents a significant opportunity to improve CdTe device efficiency.

thin film

experimental

CdTe

doping

C5

loughborough




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