Interface Engineering of Perovskite Solar Cells with Air Plasma Treatment for Improved Performance

Abstract

For high-efficiency perovskite solar cells (PSCs), interface engineering becomes critical for carrier collection from the active perovskite material to the transport layer. To enhance the power conversion efficiency (PCE), herein we demonstrate a novel method named surface plasma treatment on a mesoporous TiO electron-transport layer (ETL) to improve electron extraction and transport properties at the perovskite/TiO interface. According to the XPS results, the plasma treatment induced a partial reduction of Ti to Ti within the TiO lattice and increased the concentration of oxygen vacancies on the TiO surface. Ultraviolet photoelectron spectra (UPS) show that the Fermi level of TiO upshifts about 0.2 eV which may effectively promote carrier separation and transfer at the perovskite/TiO interface. In addition, these created donor levels of Ti and oxygen vacancies donate extra electrons, increasing the conductivities of TiO films and which could further promote transport. The time-resolved photoluminescence spectra (TRPL) confirm that the decay time decreases dramatically from 656 ns to 235 ns after 90 s plasma treatment, which indicates a more efficient electron-transfer process. Based on all the above-mentioned results, a remarkable enhancement in cell efficiency was obtained, such that the average efficiency was improved from 11.5 % to 14.3 % under AM 1.5G irradiation (100 mW cm ).

Double‐Sided Surface Passivation of 3D Perovskite Film for High‐Efficiency Mixed‐Dimensional Perovskite Solar Cells

“…Similar valence band shifts have been reported for other 2D passivation layers3a and may contribute to enhanced hole extraction in the passivated devices. On the other hand, considering the perovskite/ETL interface, since the ETL is identical for all devices, the elevated VBM associated with the passivation layer increases the VB energy gap at the interface with the ETL, potentially contributing to improved hole blocking compared to reference devices.…”

Removal of Surface Oxygen Vacancies Increases Conductance Through TiO2 Thin Films for Perovskite Solar Cells

“…(iii) A signal at 532.2 eV originates from oxygen in −OH groups and adsorbed CO 2 (green curve Figure 6). 23…”

“…Upon up-shifting the Fermi level, this results in a better band alignment with the perovskite layer and an increase of the charge transfer to TiO 2 . 23 In addition, Cojocaru et al describe an increased short-circuit photocurrent density and open-circuit voltage in PSC with increased surface oxygen vacancies. 24 Rahman et al investigated TiO 2 nanoneedles by means of impedance spectroscopy.…”

Perovskite Solar Cells with Low-Cost TiO2 Mesoporous Photoanodes Prepared by Rapid Low-Temperature (70 °C) Plasma Processing

“…50 For example, Ma et al showed that partial reduction of Ti 4+ to Ti 3+ in m-TiO 2 by plasma results in an increased concentration of oxygen vacancies and consequently an improvement in PCE from 11.5 to 14.3%. 51 In addition, Cojocaru et al have reported on increased short-circuit photocurrent density and open-circuit voltage in PSCs with increased surface oxygen vacancies. 52 Other approaches to plasma-treated photoanodes include CO 2 , 53 H 2 , 53 He, 53 and Ar 54 plasmas rendering various effects.…”