Substrate Induced p–n Transition for Inverted Perovskite Solar Cells

Abstract 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.