Dopant-Free Partial Rear Contacts Enabling 23% Silicon Solar Cells

Over the past five years, there has been a significant increase in both the intensity of research and the performance of crystalline silicon devices which utilize metal compounds to form carrier-selective heterocontacts. Such heterocontacts are less fundamentally limited and have the potential for lower costs compared to the current industry dominating heavily doped, directly metalized contacts. A low temperature (<= 230 degrees C), TiOx /LiFx/Al electron heterocontact is presented here, which achieves m Omega cm(2) scale contact resistivities p(c) on lowly doped n-type substrates. As an extreme demonstration of the potential of this heterocontact, it is trialed in a newly developed, high efficiency n-type solar cell architecture as a partial rear contact (PRC). Despite only contacting approximate to 1% of the rear surface area, an efficiency of greater than 23% is achieved, setting a new benchmark for n-type solar cells featuring undoped PRCs and confirming the unusually low p(c )of the TiOx,/LiFx,/Al contact. Finally, in contrast to previous versions of the n-type undoped PRC cell, the performance of this cell is maintained after annealing at 350-400 degrees C, suggesting its compatibility with conventional surface passivation activation and sintering steps.