Recent Advance in Solution‐Processed Organic Interlayers for High‐Performance Planar Perovskite Solar Cells

: Planar heterojunction perovskite solar cells (PSCs) provide great potential for fabricating high-efficiency, low-cost, large-area, and flexible photovoltaic devices. In planar PSCs, a perovskite absorber is sandwiched between hole and electron transport materials. The charge-transporting interlayers play an important role in enhancing charge extraction, transport, and collection. Organic interlayers including small molecules and polymers offer great advantages for their tunable chemical/electronic structures and low-temperature solution processibility. Here, recent progress of organic interlayers in planar heterojunction PSCs is discussed, and the effect of chemical structures on device performance is also illuminated. Finally, the main challenges in developing planar heterojunction PSCs based on organic interlayers are identified, and strategies for enhancing the device performance are also proposed.