Round Robin Session

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

Steps Develop procedures Do black box round

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

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.

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

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 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

Issues Package size Simulator defines the area a problem Needs – Need to identify host -NREL will host – Participants – 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

Spectral Error (can be large) – Possible error if not included