Improved Efficiency of Perovskite Solar Cells Using a Nitrogen-Doped Graphene-Oxide-Treated Tin Oxide Layer

Abstract

Tin oxide (SnO2) is widely adopted as an electron transport layer in perovskite solar cells (PeSCs) because it has high electron mobility, excellent charge selective behavior owing to a large band gap of 3.76 eV, and low-temperature processibility. To achieve highly efficient SnO2-based PeSCs, it is necessary to control the oxygen vacancies in the SnO2 layer, since the electrical and optical properties vary depending on the oxidation state of Sn. This study demonstrates that the performance of PeSCs may be improved by using nitrogen-doped graphene oxide (NGO) as an oxidizing agent for SnO2. Since NGO changes the oxidation state of the Sn in SnO2 from Sn2+ to Sn4+, the oxygen vacancies in SnO2 can be reduced using NGO. Multiple devices are fabricated, and various techniques are used to assess their performance, including X-ray photoelectron spectroscopy, dark current analysis, and the dependence of the open-circuit voltage on light intensity. Compared with the average power conversion efficiency (PCE) of control devices, PeSCs with SnO2:NGO composite layers exhibit greater PCEs with less deviation. Therefore, the introduction of NGO in a SnO2 layer can be regarded as an effective method of controlling the oxidation state of SnO2 to improve the performance of PeSCs.

Recent progress of graphene‐based materials for efficient charge transfer and device performance stability in perovskite solar cells

“…The oxygen vacancy in the SnO 2 layer must be controlled, as the electrical and optical properties vary depending on the oxidation states of Sn in order to encounter trap state issues, which could cause charges recombination and device hysteresis. Hong and team 94 proposed the doping method via incorporation of nitrogen GO (NGO) to SnO 2 ETL as an oxidizing agent for controlling the SnO 2 oxidation state to increase its electrical conductivity. NGO is capable of passivating the oxygen vacancies in SnO 2 by switching the oxidation state of Sn in SnO 2 from Sn 2+ to Sn 4+ .…”

“…and team94 proposed the doping method via incorporation of nitrogenGO (NGO) to SnO 2 ETL as an oxidizing agent for controlling the SnO 2 oxidation state to increase its electrical conductivity. NGO is capable of passivating the oxygen vacancies in SnO 2 by switching the oxidation state of Sn in SnO 2 from Sn 2+ to Sn 4+ .…”

Focussed Review of Utilization of Graphene-Based Materials in Electron Transport Layer in Halide Perovskite Solar Cells: Materials-Based Issues

“…There have been extensive works on GBMs for the ETL [17][18][19][20][23][24][25][26][27]39,43,55,56,60,61,[63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81]] that is sandwiched between the transparent conducting oxide (TCO) anodic substrate (layer 1) and the perovskite (layer 3), as shown in Figure 1b. ETL materials, such as TiO 2 , SnO 2 , ZnO, PCBM, SrTiO 3 + Al 2 O 3 , and Fe 2 O 3 , have been modified using GR, GO, RGO, and GQDs.…”

“…As these phases are deposited sequentially, with the ETLs being deposited first, and then heat treated, the ETL characteristics also can affect the wetting, recrystallization, and nanostructural development of perovskites through surface energy effects [17][18][19][20][21][22]. The characteristics that define a high-quality ETL are high electrical conductivity, high electron mobility, rapid electron extraction and transfer, wide band gap, close conduction band minimum (CBM) energy levels (lower than that of the perovskite and higher than that of the anode), wettability by the perovskite precursor, and uniform nanostructure (flat, dense, and homogeneous) [23][24][25][26][27].…”

Interfacial Defects Change the Correlation between Photoluminescence, Ideality Factor, and Open‐Circuit Voltage in Perovskite Solar Cells

“…However, some reports showed an opposite correlation, particularly when interface engineering is implemented at the bottom interface, making the PL analysis for understanding the changes in V oc controversial. [ 32–35 ]…”