Physics projects for Y3 and Y4 students

Project description

Quantitative measurements of Light-Emitting Diodes using an integrating sphere method

(supervisor: Chris Finlayson)

Nature of project: experimental, experimental

Available to students on full-time physics degree schemes or joint students.

Project description and methodology

The quantitative measurement of light emission from semiconductors is a critical issue when characterizing new materials and devices for applications as wide as LEDs, lasers and solar cells.

A light-emitting diode (LED) is a semiconductor device that emits light when injected electrons in the active layer(s) recombine with holes, releasing energy in the form of electroluminescence. The photon energies (corresponding to the colour spectrum of the light) is determined by the bandgap energy of the semiconductor.[1] The key parameters when considering the device operation and performance are- i) light spectrum, ii) the quantum-efficiency (ratio of photons generated to charges injected), and iii) luminous efficacy (perceived brightness per unit input power).[2,3]

In this experimental project, the student will characterise these parameters using an "integrating sphere"[4]; a calibrated instrument which allows luminescent emission to be collected over all solid angles. The student will modify the instrumental design to allow the incorporation and study of the electroluminescence from LEDs

A successful project will develop beyond the above in one/some of the following directions:
As an extension, students may develop a full testing protocol for the LEDs studied, incorporating both light (Cd/V) and current (J/V) output characteristics, allowing comparison with industry specification.

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

This project is only available as a Y3 project.

Please speak to Chris Finlayson (cef2) if you consider doing this project.

Initial literature for students:

  1. https://www.britannica.com/technology/LED
  2. http://www.excilight.com/technology/oled-101/quantifying-oleds
  3. F. Maasoumi et al., npj Flexible Electronics, vol.2, Article number: 27 (2018)
  4. J. Tomes & C.E. Finlayson, Eur. J. Phys., vol.37, 055501 (2016)

Novelty, degree of difficulty and amount of assistance required

The scientific content involved in this project is highly suitable for the average Y3 physics student. Training on a number of pieces of equipment will be given as required.

Project milestones and deliverables (including timescale)

milestoneto be completed by
Experimental design outlineChristmas
Rig/Instrument constructionend of February
Calibration and testing completemid-March
Data collation and analysisEaster

Students taking this project will have to submit a full risk assessment form