Highly stable and efficient lead-based perovskite solar cell with tin-oxide electron transport layer

Abstract

Fossil fuels still hold a predominant position in global energy consumption. However, they have caused various environmental and societal problems. The world’s energy demand has been increasing tremendously over the years, which results in an urgent need to utilize more alternative energy sources. In the quest for sustainable and renewable energy sources, solar energy is known to be a promising solution to address the growing global energy demand and environmental concerns. Photovoltaics (PV) refers to applications harvesting solar energy and generating electricity. Over the past few decades, the capacity and technologies of PV have grown noticeably with various materials and architectures being studied to enhance efficiency, stability and cost-effectiveness. Among generations of PV cells, halide perovskite solar cells (PSCs) in the third generation show remarkable properties that set them apart from conventional photovoltaic technology. Even though perovskite solar cells are still a new PV technology compared to other solar cells, it has gained interest from scientists and researchers worldwide. Its power conversion efficiency (PCE) has increased exponentially over a short period of time, from 3.8 % in 2009 to 26.1 % in 2023. Despite many advantages, a well-known obstacle preventing perovskite solar cells from viable commercialization is their instability because of many degradation pathways. The main focus of this thesis is the effect of the nanoparticle tin-oxide-based electron transport material on the performance of lead-halide perovskite solar cells. Electron transport materials (ETMs) in solar cells facilitate the movement of electrons generated by absorbed sunlight towards the electrical contacts, enabling the conversion of solar energy into electricity. By using a suitable ETM in a solar cell, electron mobility within the cell can be improved. Titanium-oxide-based electron transport material, one of the most common ETMs for lead-halide perovskite solar cells, is chosen as a reference to compare with the tin-oxide-based ETM. Tin-oxide (SnO2) enhances charge mobility due to a deeper conduction band than titanium-oxide (TiO2). The manufacturing process of the SnO2-based perovskite solar cells does not require high temperatures - a common disadvantage in the production of TiO2-based solar cells. In this thesis, two different concentrations of nanoparticle stock solution were assumed and tested to choose the concentration resulting in more efficient perovskite solar cells. The nanoparticle stock solution was diluted with ultra-clean H2O to a concentration of 2.67 % from the stock solution when assuming concentrations of 15 % and 20 %. Two types of substrate FTO and ITO were tested to observe which one is more suitable for nanoparticle SnO2-based perovskite solar cells. PV characteristics and quantum efficiency measurements were assessed one day after solar cell fabrication had been completed. The cells with the best performance were chosen as samples for testing stability. Maximum power point tracking (MPPT) was conducted in an inert atmosphere. The highest power conversion efficiency of 14.6 % was achieved on FTO substrates with SnO2 2.67 % concentration. The average PCE was 11.30 %. The fill factor (FF) values could reach 70.4 % with the average FF being 56.8 %. The external quantum efficiency (EQE) of SnO2-based PSC was approximately 80 %. The SnO2-based devices retained approximately 60 % of their initial PCE after 100 hours, which indicates their high stability. Despite the lower results compared to TiO2-based devices, SnO2-based devices showed promising performance in PCE and stability. Further research could focus on SnO2 recipes and their effect on the performance and stability of perovskite solar cells.