Round Robin Session

1. Round Robin Session

2. Ways of Comparison • Stable Samples • OPV • Black box – unknown with filters over Si • Need to measure QE and Efficiency • Send a KG5 reference cell • Need to send out a guideline on how to measure efficiency

3. Steps • Develop procedures • Do black box round

4. Measurement Procedures • How to measure efficiency – Keith, Matt, Moritz (1-2 months) • How to measure an IV curve (is bias rate to high – does it matter which way you sweep • Area definition jsc with and without an aperture • Small under a cm2 • If we are a large area technology 1cm2 is a minimum • Physics community does not want 1 cm2 • Key is to define an aperture approach. Under a certain area must use an aperture. Should be round or square or rectangle • How you make contact can matter – edge or top. (In on SnOx ext around boarder) Add additional metal. Separate voltage and current contacts a no/no • If no aperture then must be over 1 cm2 • Should their be a minimum area ? • Aperture needs to be thin, could be part of metallization mask • User should place the aperture • Need to include details of cells, filters and light sources • IPCE data needs to be included – Sean will provide spread sheet for IPCE to current • Need to make sure that the QE and Jsc are consistent • Jsc from spectral response based on inter-comparison no better than +/- 10% • Do measurement as a function of light intensity is useful but not required • Submitted cells need to have either the aperture on them or room to place an aperture • ASTM G173 will be new solar spectrum standard • Include a bibliography of useful references etc. • Try to define low cost simulator and QE system

5. Light sources • Filaments (kg5 or kg filter) can be pretty solar like • Should run a same current and change distance to change the light level • Xenon arc expensive and not good data • Good procedures compensate for spectral error • Reference Cell • KG5 filtered Si cell – filter can be on detector as well. Use other filters to match device.

6. OPV cert. Measurements • Ultimately 1 cm2 • No real package requirements – need to define aperture --- mandatory under 1 cm2 • Minimum area?, Aspect ratio cannot be to high (<100:1) • Historically stability has not been an issue • Amorphous a stabilized number • Dark wait time – could be up to 4 weeks – nitrogen box overpressured • How much time in air and light – 1 min in each for both - time constants

7. Round Robin • If OPV then sample would have to be stable of each cycle. • First round robin send out KG filtered Si solar cell. • Hammatsu can build a set of “identical” devices. • Have a device for P3HT and for Low Band Gap, CuPc/C60 • Geometry constraints could be a problem • Start process now – have measurements done in 6 month (october 1 to send out devices) and write up follows (published in journal) – first send out devices and get data back and then feed back actual data • There will be a second round in about a year to be better defined then but the study will get an OPV device from commercial supplier • Participant – blanket email to see who wants to participate. Up to 30 possible. • Participants are identified but not their data then there is a paper for original state of the measurements and a second

8. Issues • Package size • Simulator defines the area a problem • Needs • Need to identify host -NREL will host • Participants – email response • Package – 1 cm2 should work – need to define rest with participants. • Standardized spectra – CuPc/C60, P3HT, Low band gap • One for P3HT, one for long wavelength polymer, one for other • NREL/DU will do P3HT/ • Heeger/Konarka/Plextronics Small band gap • Moritz Riede small molecule • Put temperature sensor in the package • Do we require a QE measurement for the cells. – yes • If it is a good blind experiment then no one sees data till the end • How often do you repeat • We keep the packages around and can send them back out for requalification • Temperature – 25

9. Spectral Error (can be large) • Possible error if not included