Abstract
Perovskite solar cells that use carbon (C) as a replacement of the typical metal electrodes, which are most commonly employed, have received growing interest over the past years, owing to their low cost, ease of fabrication and high stability under ambient conditions. Even though Power Conversion Efficiencies (PCEs) have increased over the years, there is still room for improvement, in order to compete with metal-based devices, which exceed 25% efficiency. With the scope of increasing the PCE of Carbon based Perovskite Solar Cells (C-PSCs), in this work we have employed a series of ammonium iodides (ammonium iodide, ethylammonium iodide, tetrabutyl ammonium iodide, phenethylammonium iodide and 5-ammonium valeric acid iodide) as additives in the multiple cation-mixed halide perovskite precursor solution. This has led to a significant increase in the PCE of the corresponding devices, by having a positive impact on the photocurrent values obtained, which exhibited an increase exceeding 20%, from 19.8 mA/cm2, for the reference perovskite, to 24 mA/cm2, for the additive-based perovskite. At the same time, the ammonium iodide salts were used in a post-treatment method. By passivating the defects, which provide charge recombination centers, an improved performance of the C-PSCs has been achieved, with enhanced FF values reaching 59%, which is a promising result for C-PSCs, and Voc values up to 850 mV. By combining the results of these parallel investigations, C-PSCs of the triple mesoscopic structure with a PCE exceeding 10% have been achieved, while the in-depth investigation of the effects of ammonium iodides in this PSC structure provide a fruitful insight towards the optimum exploitation of interface and bulk engineering, for high efficiency and stable C-PSCs, with a structure that is favorable for large area applications.
Highlights
Perovskite Solar Cells (PSCs) have been in the spotlight of research over the past 10 years, which has led to significant improvements in the technology’s output
In order to evaluate the effect that the addition of ammonium iodides in the perovskite precursor solution has on the resulting perovskite crystals’ properties, X-ray Diffraction (XRD) measurements have been performed in full stack devices of the triple mesoscopic structure (c-TiO2/mesoporous TiO2 layer (m-TiO2)/ZrO2/perovskite/C) and the results have been analyzed (Figure 1)
In the direction of ammonium iodides as additives, after the incorporation of ammonium iodide (AI) in the precursor solution, an increase in the absorbance, combined with a decreased charge transfer resistance, has led to Carbon based Perovskite Solar Cells (C-PSCs) with Power Conversion Efficiencies (PCEs) of 10.3%, increased by 33% compared to the reference perovskite, and with a low hysteresis index of 0.18, compared to 0.31 for the reference
Summary
Perovskite Solar Cells (PSCs) have been in the spotlight of research over the past 10 years, which has led to significant improvements in the technology’s output. Non-radiative recombination, known as Shockley–Read–Hall (SRH), that accounts for the largest portion of losses, occurs both at the interfaces between the perovskite and the charge transport layers, as well as the perovskite bulk and the grain boundaries [13,14]. The most promising approaches that have been used in order to minimize the trap-assisted non-radiative recombination losses are the control of the perovskite crystallization, through the engineering of the perovskite composition and the use of additives, the defect passivation and interface engineering and the formation of graded 2D/3D junctions, by applying post-treatment methods [15,16,17]. By applying the aforementioned techniques, increases in the PCE have been achieved, reducing the gap between the theoretical and realistic PCEs obtained
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