Efficiency Enhancement of Inverted Structure Perovskite Solar Cells via Oleamide Doping of PCBM Electron Transport Layer

Abstract

An amphiphilic surfactant, oleamide, was applied to dope the PCBM electron transport layer (ETL) of inverted structure perovskite solar cells (ISPSCs), resulting in a dramatic efficiency enhancement. Under the optimized oleamide doping ratio of 5.0 wt %, the power conversion efficiency of the CH3NH3PbIxCl(3-x) perovskite-based ISPSC device is enhanced from 10.05% to 12.69%, and this is primarily due to the increases of both fill factor and short-circuit current. According to the surface morphology study of the perovskite/PCBM bilayer film, oleamide doping improves the coverage of PCBM ETL onto the perovskite layer, and this is beneficial for the interfacial contact between the perovskite layer and the Ag cathode and consequently the electron transport from perovskite to the Ag cathode. Such an improved electron transport induced by oleamide doping is further evidenced by the impedance spectroscopic study, revealing the prohibited electron-hole recombination at the interface between the perovskite layer and the Ag cathode.

Charge‐Carrier Balance for Highly Efficient Inverted Planar Heterojunction Perovskite Solar Cells

“…[29] As shown in Figure 5c, the Voc of the balanced device had a slower photovoltage decay than the reference, suggesting a lower charge carrier recombination rate and, thus, more balanced charge carrier transport. [41] Suppressed charge carrier recombination was also confirmed by the dark current measurements, [31] as shown in Figure 5d. The dark current densities of the balanced devices were almost two orders of magnitude lower than those of the reference ones.…”

“…The PCE enhancement can be attributed to the increased Voc and FF, which benefit from the improved film morphology. [15,31] However, further increasing the concentration of PMMA did not improve the device performance, due to the insulating characteristic of PMMA.…”

“…[29] Moreover, the aggregation behavior of PCBM could also lead to a poor morphology [30] and a poor ESC film could easily lead to inefficient electron transport and a decrease in the photovoltaic performance. [31] To improve the film morphology, we introduced 1.0 wt% PMMA into PCBM to form the PCBM:PMMA hybrid ESC. was achieved corresponding to the PMMA concentration of 1.0 wt%.…”

“…For the PCBM layer, although PMMA is insulating, trace introduction of PMMA could help to suppress the aggregation of PCBM and enhance the interfacial contact with the perovskite, [29,30] leading to increased electron extraction at the perovskite/PCBM interface. [15,31] This promoted a more efficient charge carrier collection from the perovskite to the electrode with less energy loss. [13] It should be noted that, the treated/modified samples had more balanced fast decay lifetimes (2.95 ns at HSC and 2.97 ns at ESC, respectively).…”

Efficient Perovskite Hybrid Solar Cells via Ionomer Interfacial Engineering

“…[ 13,14 ] In fact, the electrical conductivities of a TiO x EEL in MS pero-HSCs and phenyl-C 61 -butyric acid methyl ester (PC 61 BM) EEL in PHJ pero-HSCs are several orders of magnitude lower than those of the hole-extraction layer (HEL) counterparts, [15][16][17][18][19][20] resulting in an inferior electron-collection effi ciency, lower shortcircuit current density ( J SC ), and lower fi ll factor (FF). [ 11,21 ] On the other hand, it has been reported that the contact between the perovskite layer and the EEL was poor due to the rough surface of the solution-processed perovskite layer, [ 22,23 ] which inevitably deteriorates the electron-extraction effi ciency, creates charge-carrier recombination, and simultaneously introduces large leakage currents. [24][25][26] In order to circumvent these problems, studies have been focused on the interfacial modifi cation of the contact between the EEL and the cathode.…”