|Paths for maximal light incoupling and excellent electrical performance in silicon heterojunction solar cells|
|Mathieu Boccard1, Luca Antognini1, Jean Cattin1, Julie Dréon1, Olivier Dupré1, Angela Fioretti1, Jan Haschke1, Raphaël Monnard1, Vincent Paratte1, Esteban Rucavado1, Laurie-Lou Senaud2, Sihua Zhong1, Bertrand Paviet-Salomon2, Monica Morales-Masis1, Matthieu Despeisse2, Christophe Ballif1,2
1EPFL, Neuchâtel, Switzerland
/2CSEM, Neuchâtel, Switzerland
We review here recent progress on high-efficiency, high-current silicon heterojunction solar cells. We give several industry-relevant paths towards simultaneous reaching of high current densities and excellent electrical properties, both for 2-side-contacted and interdigitated-back-contacted (IBC) devices. For the latter, record efficiencies were demonstrated in recent years, yet with non-industrially-viable processes. We discuss here progress in tunnel IBC architecture—showing extraordinary simple process with a one-mask and one-alignment approach—still demonstrating efficiency values above 24%. We reveal here some key requirements to combine highly crystalline doped layers with excellent passivation enabling high voltages and low series resistance. For 2-side contacted solar cells, we will review progress on transparent electrodes and contact layers, that allows improving light management (with Jsc > 40 mA/cm2 in each individual case) while maintaining passivation and reducing resistive losses. Zr-doped In2O3 provides improved transparency both in the UV and IR parts of the spectrum thanks to a high carrier density and mobility. Thin yet high-crystallinity microcrystalline silicon doped layers provide lower absorption and advantageous refractive index matching compared to amorphous silicon, together with improved electrical properties. Finally, recent results on metal-oxide-based electron and hole-selective contacts (including ZnO and MoOx) will be discussed.