Development of crystalline silicon based metal wrap through (MWT) solar cells for low concentrator (2-30x) applications

One of the main barriers on the way to mass production of concentrator silicon solar cells is the lack of industrially feasible process sequences. Therefore, a concentrator silicon based Metal Wrap Through (CMWT) solar cell completely processed at the Fraunhofer ISE PhotoVoltaic Technology Evaluation Center (PV-TEC) is introduced. This means no clean room or photolithographic steps are necessary. Under one-sun conditions, a conversion efficiency of 18.6% could be reached which is so far the highest efficiency reported for a MWT silicon solar cell. The highest efficiency achieved was 19.5% at 6 suns and even 18.1% at 23 suns. The series resistance as major loss mechanism concentrator solar cells are suffering from is the main focus in this work. Concerning this matter an investigation of the Light induced Plating (LiP) step and furthermore a detailed analysis of the contributions to the series resistance is presented. A simulation tool containing an analytical series resistance model has been developed and a 2-diode-model was added providing the calculation of the efficiency and fill factor dependent on the concentration at given parameters.