Solution-processable perylene diimide-based electron transport materials as non-fullerene alternatives for inverted perovskite solar cells

Perylene diimide derivatives with different functional groups (OR) in the bay position were synthesised (PDI-1, OR = OC6H4OMe; PDI-2, OR = OC(6)H(4)CH(2)CH(2)NHBoc; PDI-3, OR = OC6H4CO2Me) and their optoelectronical properties were characterised. The derivatives were applied as alternative electron transport materials (ETMs) to replace the commonly used PCBM in inverted perovskite solar cells (PSCs). Devices with the structure ITO/PTAA/Cs-0.04(MA(0.17)FA(0.83))(0.96)Pb(I0.83Br0.17)(3)/ETM/Ag (ETM = PCBM or PDI-1, -2 or -3) were fabricated through solution processing techniques. A competitive power conversion efficiency (PCE) of 16.8% was obtained for the PDI-3-based device, which was comparable to the PCBM-based device with PCE of 17.3%. It was found that the electronic nature of the functional groups plays an important role in the charge extraction and band alignment of these small molecular semiconductors.