European thin film tandem device proficiency test - practical outcomes and preliminary results

Within the European FP7 project CHEETAH, a thin-film tandem solar cell round-robin proficiency test was conducted between 13 testing laboratories, plus the European Solar Test Installation (ESTI) of the European Commission's Joint Research Centre as reference laboratory. The purpose of this RR was to compare testing facilities and procedures of the involved partners against the reference measurement by ESTI. In total, five cells were measured. Three tandem devices (a-Si:H/μc-Si) and a single-junction device representing the top (a-Si:H) and the bottom (μc-Si) cells, respectively, were provided by one partner. All cells (with active area of 1 cm2) were mounted in a standardised housing with connection sockets for I-V measurements and a Pt-100 temperature sensor. The cells were initially stabilised and calibrated at ESTI and afterwards circulated. The characterisation was done by I-V measurements at Standard Test Conditions and EQE measurements. ESTI checked and re-calibrated the cells at the end of the RR before and after further stabilization. Here we report on some preliminary I-V measurement results. A number of acquired or conversely still necessary improvements are discussed for the organisational point of view along with some measurement requirements that are still missing or that are not sufficient at many participating laboratories.