Designing for ESD survivability of a monolithically protected GaInP2/GaInAs/Ge solar cell

We report on the design and performance of a monolithically protected GaInP₂/Ga(In)As/Ge cell. This solar cell known as the ZTJM is a companion cell to the 30% class GaInP₂/Ga(In)As/Ge ZTJ solar cell. The ZTJ cell is characterized by a beginning of life (BOL) maximum power point efficiency of 29.5% (135.3 mW/cm²) under simulated AM0 illumination with an operating temperature of 28°C. The primary design objectives of the ZTJM cell were to maintain performance parity with the ZTJ cell and to demonstrate improved electrostatic discharge (ESD) hardness of the bypass diode relative to those in previous monolithically protected triple junction products. Through the course of the diode development we identified two key factors required for ESD robustness. With these findings we have achieved a monolithically protected GaInP₂/Ga(In)As/Ge cell with an average 1-sun AM0 efficiency of 29% capable of withstanding at least 10 successive pulses of 30 A intensity and 100 us duration.