posted on 2021-09-03, 21:06authored byYifang Qi, David Ndaleh, William E. Meador, Jared H. Delcamp, Glake Hill, Nihar Ranjan Pradhan, Qilin Dai
The
interface between [6,6]-phenyl C61-butyric acid
methyl ester (PC61BM) and the electrode has a critical
effect on the performance of inverted perovskite solar cells (PSCs).
Three organic cationic cyanine dye molecules with different highest
occupied molecular orbital (HOMO) and lowest unoccupied molecular
orbital (LUMO) states are designed to passivate the PC61BM and Ag electrode interface to improve PSCs performance. The effects
of energy-level alignment and the interfacial charge transfer resistance
on the device performance are compared and studied. The dye interface
passivation layer significantly reduces charge recombination. Moreover,
the ClO4– anions associated with the
dye molecules improve the charge extraction and charge transport in
the devices. Reduced interface charge recombination and improved charge
transport are confirmed by photoluminescence (PL), time-resolved photoluminescence
(TRPL), electrochemical impedance spectra (EIS), and charge-only device
performance studies. The PSCs with one of the dyes as an interface
passivation layer show an optimized power conversion efficiency (PCE)
of 19.14% with an open-circuit voltage (Voc) of 1.09 V, a short-circuit current density (Jsc) of 22.87 mA/cm2, and a fill factor (FF) of 76.81%.
The devices maintain over 90% of the initial PCE for 120 h of storage
under an ambient environment (25 °C and 30 ± 5% relative
humidity (RH). The use of small dye molecules as an interface passivation
layer to reduce charge recombination in PSCs represents a paradigm
for improving the performance and stability of PSCs.