CTMOD: A cell-to-module modelling tool applied to optimization of metallization and interconnection of high-efficiency bifacial silicon heterojunction solar module

Today, an increasing number of companies are working with heterojunction technology because of its higher efficiency potential and decreasing LCOEs compared to traditional solar cells [1] [2]. One of the major challenges for SHJ solar cells is the use of low temperature silver paste for metallization because of 1) their lower conductivity and 2) their need of alternative interconnection strategies as described by Faes et. al. [2]. As heterojunction technology is relatively new and as new wafer sizes are about to be adopted, metallization and interconnection are facing challenges and opportunities [3]. To screen quickly the multiple possibilities, a specific modelling for heterojunction has to be developed. The parameters describing the metallization and interconnection of a module are numerous and highly interdependent. In this field, performance optimization is always a compromise to be made mainly between the additional series resistance of the elements (TCO, finger, busbar, ribbons) and their impact on the photo-generated current. Optimal results are expressed in term of finger width, grid pitch, number of busbar and ribbons, section of ribbons, etc. Even under standard conditions (STC), the optimizations are obviously dependent on the parameters of the non-metallized cell. Also, the results differ whether the optimization criterions include the cost of the individual elements ((sic)/Wp). For these reasons, CTMOD, a multidimensional prediction model of the performance and material cost of each possible architecture, is essential.