Abstract
The design of electron transport layers (ETLs) with good optoelectronic properties is one of the keys to the improvement of the power conversion efficiencies (PCEs) and stability of perovskite solar cells (PSCs). Titanium dioxide (TiO2), one of the most widely used ETL in PSCs, is characterized by low electrical conductivity that increases the series resistance of PSCs, thus limiting their PCEs. In this work, we incorporated tin oxide (SnO2) into titanium dioxide (TiO2) and studied the evolution of its microstructural and optoelectronic properties with SnO2 loading. The thin films were then integrated as ETLs in a regular planar Formamidinium (FA)-rich mixed lead halide PSCs so as to assess the overall effect of SnO2 incorporation on their charge transport and Photovoltaic (PV) characteristics. Analysis of the fabricated PSCs devices revealed that the best performing devices; based on the ETL modified with 0.2 proportion of SnO2; had an average PCE of 17.35 ± 1.39%, which was about 7.16% higher than those with pristine TiO2 as ETL. The improvement in the PCE of the PSC devices with 0.2 SnO2 content in the ETL was attributed to the improved electron extraction and transport ability as revealed by the Time Resolved Photoluminescence (TRPL) and Electrochemical Impedance Spectroscopy (EIS) studies.
Highlights
The charge carrier collection efficiency and the overall power conversion efficiency (PCE) of Perovskite solar cells (PSCs) depends on the effectiveness of light absorption [6] and the accompanying charge carrier dynamics [7] that occur within the PSC structure
To understand the effect of electron transport layers (ETLs) modification on the electron transport dynamics of the PSCs, we investigated the variation of the optoelectronic properties of perovskite films deposited on pristine TiO2 and SnO2 -TiO2 ETLs through UV-Vis, steady state photoluminescence (PL), time resolved photoluminescence (TRPL) and space charge limited conduction (SCLC) techniques
Pristine TiO2 and SnO2 -modified TiO2 thin films with different proportions of SnO2 have been studied as ETLs in FA-rich planar PSCs
Summary
Technologies with photoconversion efficiencies comparable to those of the conventional crystalline silicon based solar cells [1,2] They consist of photoactive perovskite layers that are sandwiched between two oppositely doped charge transport layers (CTLs) to form regular (n-i-p) or inverted (p-i-n) device architectures with electrodes on either side [3,4]. Owing to the exceptional optoelectronic properties of the perovskite active layer such as high light absorption ability [6], low exciton binding energies [8], balanced ambipolar charge carrier transport [7,9], high defect tolerance and long carrier diffusion lengths [10], the charge carriers in the Active Layer (AL) are effectively generated, separated and transported to the interface with CTLs when PSCs are illuminated [11]
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