Interface materials for perovskite solar cells

Perovskite solar cells exhibit great potential to become commercial photovoltaic technology due to their high power conversion efficiency, low cost, solution processability, and facile large-area device manufacture. Interface engineering plays a significant role to optimize device performance. For the anode in the inverted devices, this review introduces the progress on the modification of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) including chemical structure alteration, physical doping, and solution treatment. We present the recent advances of dopant-free hole transport materials widely applied in mesoporous and conventional devices, outlining their innovation with novel molecular design concepts toward promising material properties, and device performance. For the cathode, various metal oxide and organic electron transport materials are covered and the different modification strategies and related mechanisms are highlighted. Most importantly, simple synthesis process, inexpensive raw materials and highly reproducible photovoltaic performance are the main consideration for the design of all the interface materials. Finally, an outlook and some suggestions regarding the future interface engineering are proposed based on the summary of the current development status and working mechanism of interface materials.