Measurement of TiO2/p-Si Selective Contact Performance Using a Heterojunction Bipolar Transistor with a Selective Contact Emitter

In a photovoltaic device, the evaluation and understanding of carrier-selective contacts are difficult, because in both terminals the current measured represents the sum of both electron and hole currents at that contact. We seek to independently know the electron current and hole current across a carrier-selective contact. In this work, we demonstrate a heterojunction bipolar transistor structure using the selective contact as the emitter-base junction, allowing one to separately measure the electron and hole currents at that contact. The method is then used to evaluate the properties of a TiO
₂
/p-type crystalline Si electron-selective heterojunction contact, and the information learned is used to understand a TiO
₂
/p-Si heterojunction PV cell, where the TiO
₂
/p-Si replaces the n
⁺
-p junction.