Phosphonic Acid Modification of the Electron Selective Contact: Interfacial Effects in Perovskite Solar Cells

Abstract

The role electron-transport layers (ETLs) play in perovskite solar cells (PSCs) is still widely debated. Conduction band alignment at the perovskite/ETL interface has been suggested to be an important role for the performance of the solar cells. However, little is known about the effects of work-function shifts on the solar-cell performance, and specifically, the open-circuit voltage (V OC). Here, the effects of surface modification of SnO2 ETLs using polar phosphonic acids are investigated, including the effects on work function, surface energy, device performance, and device stability in inert atmosphere. The phosphonic acid modifications did not have a large effect on V OC; however, a sharp decrease in the overall device performance was found, mostly due to reduced fill factors. When exposed to conditions of low oxygen concentration, the phosphonic acid surface modified devices yielded current–voltage (J–V) curves with considerably lower hysteresis than those based on unmodified SnO2. This suggests that this modification method may be valuable for achieving stabilized power conversion efficiency without hysteresis.

Realizing Reduced Imperfections via Quantum Dots Interdiffusion in High Efficiency Perovskite Solar Cells

“…[ 21–24 ] Various reports have detailed on a range of molecules employed for managing these interfacial ionic defects. For instance, Lewis bases containing carboxyl, [ 25 ] amine, [ 26 ] phosphonic, [ 27 ] and thiol [ 28 ] functional groups, capable of donating or sharing electrons with uncoordinated Pb 2+ ions at the surfaces and GBs, have been shown to be effective in mitigating these defects. On the other hand, Lewis acid molecules such as iodopentafluorobenzene (IPFB) passivate such defects by accepting electrons via halogen bond formation with uncoordinated halides.…”

Engineering 3D perovskites for photon interconversion applications

“…However, even encapsulated, solid-state UC devices slowly degrade over time, which in turn can be correlated to a loss in efficiency. Approaches to stabilize the perovskite film structure are related to a substitution or doping of A-, B-, or X-site ions [64][65][66][67][68], or engineering of defects, interface and microstructure [69][70][71].…”

Spray coating vs. immersion for self-assembly of gemini perfluorinated phosphonic acids on indium tin oxide

“…PA SAMs have been reported to act as a resist for wet etching [17], to protect surfaces against corrosion [2,18], to modify the work function of transparent conductive oxides [19][20][21][22], and as a patterning layer for the metallization of heterojunction solar cells [23]. Recently, PA SAMs have also been shown to improve the perovskite solar cell efficiency when used as or within charge-transporting layers [24][25][26][27].…”