Substrate Induced p–n Transition for Inverted Perovskite Solar Cells

The p- or n-type property of semiconductor materials directly determine the final performance of photoelectronic devices. Generally, perovskite deposited on p-type substrate tends to be p-type, while perovskite deposited on n-type substrate tends to be n-type. Motived by this, a substrate-induced re-growth strategy is reported to induce p- to n-transition of perovskite surface in inverted perovskite solar cells (PSCs). p-type perovskite film is obtained and crystallized on p-type substrate first. Then an n-type ITO/SnO₂ substrate with saturated perovskite solution is pressed onto the perovskite film and annealed to induce the secondary re-growth of perovskite surface region. As a result, p- to n-type transition happens and induces an extra junction at perovskite surface region, thus enhancing the built-in potential and promoting carrier extraction in PSCs. Resulting inverted PSCs exhibit high efficiency of over 25% with good operational stability, retaining 90% of initial efficiency after maximum power point (MPP) tracking for 800 h at 65 °C with ISOS-L-2 protocol.