Deposition of Reduced Graphene Oxide Thin Film by Spray Pyrolysis Method for Perovskite Solar Cell

TL;DR

This paper reports the preparation and characterization of reduced graphene oxide and titanium dioxide layers as hole and electron transport layers in perovskite solar cells, aiming to improve stability and performance.

Contribution

It introduces a spray pyrolysis method for depositing rGO as HTL and compares TiO2 layers prepared by spin coating and doctor blading as ETL in perovskite solar cells.

Findings

rGO bandgap is 2.1 eV, varies with reduction level

TiO2 bandgap reduced from 4.51 eV to 4.12 eV after adding M-TiO2

Bandgap decreases with M-TiO2 addition, indicating improved properties

Abstract

The Perovskite absorber layer, the electron transport layer (ETL), the hole transport layer (HTL), and the transparent conducting oxide layer (TCO) are the major components that make up a Perovskite solar cell. Between ETL and HTL, the absorber layer is sandwiched, on which electron-hole pairs are created after absorption of solar radiation. Despite substantial progress toward efficiency, long-term stability still remains a serious concern. Present work focuses toward contributing on the later issue by adopting Titanium dioxide (TiO2) as ETL and reduced graphene oxide (rGO) as HTL. Specifically, in the present work, we report our efforts on the preparation of compact titanium dioxide (C-TiO2) and mesoporous titanium dioxide (M-TiO2) layers as an ETL and a reduced graphene oxide thin film as a HTL. The C-TiO2 film was spin casted on FTO glass followed by casting of M-TiO2 film using Doctor Blading technique. Similarly, the rGO film was produced by spray casting over the glass substrate. The as-prepared ETL and HTL layers were characterized by measuring their optical properties (transmittance and reflectance of thin films). Then, the bandgap, Eg was extracted from reflectance and transmittance curves for ETL and HTL respectively. In the case of rGO, we found the value of Eg to be 2.1 eV, which varies between 2.7eV and 0.02eV depending upon its reduction level based on the previously reported values. Similarly, the bandgap of the C-TiO2 was 4.51 eV which was reduced to 4.12 eV after the addition of M-TiO2, which are 0.9 to 1.1 eV higher than previously reported values. However, bandgap shows decreasing trend after employing M- TiO2 over C-TiO2. In a Perovskite solar cell, both ETL and HTL will be investigated.