7-PERCENT STABLE EFFICIENCY LARGE-AREA A-SI-H SOLAR MODULES BY MODULE DESIGN IMPROVEMENT

Recent progress in series production of large area, single junction a-Si:H modules (0.4 m2) at Siemens Solar GmbH, Munich, led to high process stability and an overall yield exceeding 90%. Along with these achievements the efficiency of the modules went up considerably. The efficiency was further improved by combining (1) laser scribing technique for structuring the back side TCO of the module and (2) a cell width optimization concerning the tradeoff between the power loss due to electrode resistivity and area loss due to the number of laser scribes and total interconnect width. Efforts for additional improvements of the isolation cut at the modules edges by a subsequent chemical treatment at the front sides of the circuit and an enhancement of the photocurrent by optimizing the optical properties of the reflector material add up to an initial module efficiency of 8.9% and a stabilized efficiency of 7% for the best module. This is from our knowledge the highest value for large area a-Si:H pin modules up to now. Further improvements in cell design leading to an photodegradation of 15% for pin modules seem to be possible.