In this work, we present a comprehensive study to understand how bulk resistivity, defects and operating temperature impact the solar cell performance. Simulations indicate solar cells with excellent surface passivation benefit from substrates with high bulk resistivity as they operate at high injections. For the same defect type and defect concentration, higher lifetime is achieved for wafer with higher bulk resistivity. We fabricate silicon heterojunction lifetime samples on substrates with bulk resistivities from 1 to >15k Ocm and study the behavior of lifetime and implied parameters at different operating temperatures. The effective lifetimes increase with temperature for wafers in all bulk resistivity ranges. Temperature coefficients are shown to be independent of the bulk resistivity and the measured values are in the range of values previous reported on silicon heterojunctions manufactured for standard bulk resistivity (2-3 Ocm) wafers.