Synergistic Crystal and Interface Engineering for Efficient and Stable Perovskite Photovoltaics

Abstract

The presence of bulk and surface defects in perovskite light harvesting materials limits the overall efficiency of perovskite solar cells (PSCs). The formation of such defects is suppressed by adding methylammonium chloride (MACl) as a crystallization aid to the precursor solution to realize high‐quality, large‐grain triple A‐cation perovskite films and that are combined with judicious engineering of the perovskite interface with the electron and hole selective contact materials. A planar SnO2/TiO2 double layer oxide is introduced to ascertain fast electron extraction and the surface of the perovskite facing the hole conductor is treated with iodine dissolved in isopropanol to passivate surface trap states resulting in a retardation of radiationless carrier recombination. A maximum solar to electric power conversion efficiency (PCE) of 21.65% and open circuit photovoltage (Voc) of ≈1.24 V with only ≈370 mV loss in potential with respect to the band gap are achieved, by applying these modifications. Additionally, the defect healing enhances the operational stability of the devices that retain 96%, 90%, and 85% of their initial PCE values after 500 h under continuously light illumination at 20, 50, and 65 °C, respectively, demonstrating one of the most stable planar PSCs reported so far.

Μethylammonium Chloride: A Key Additive for Highly Efficient, Stable, and Up‐Scalable Perovskite Solar Cells

“…[65][66][67] Slightly higher efficiencies of 19-20% were recently reported for mixed-cation perovskites through the addition of excess of 5-20% MACl (molar ratio in relation to Pb 2+ ). [76,79] Even higher efficiencies were recently reported for mixed-cation, formamidiniummethylammonium perovskites. We notice here that this work is among the very few where no changes in macroscopic properties in perovskite films were observed such as absorption and photoluminescence spectra, confirming that chloride is not integrated into the perovskite lattice (Figure 8c).…”

“…[27,28] Even though there was no specific mention on the MACl effect in these two works, we wish to highlight here that the addition of 33% excess of MACl drives the precursor solution in an overstoichiometry of MA + . [79] It was previously shown by Brenes et al that water and oxygen in air (in combination with ambient light) could completely remove shallow states at the perovskite surface by forming a nanometer-thin amorphous shell of inert degradation products. [80] It seems here that Seo's group is following the MA + -excess concept.…”

“…Reproduced with permission from ref [79]. b) Statistical data for devices, without and with MACl additive.…”

Efficient Semitransparent CsPbI3 Quantum Dots Photovoltaics Using a Graphene Electrode

“…As mentioned in the literature, stability is the main challenge in the field of PSCs . Therefore, we measured the shelf‐life stability of our devices in ambient air (20% relative humidity (RH)) over 14 days.…”

Light Management in Organic Photovoltaics Processed in Ambient Conditions Using ZnO Nanowire and Antireflection Layer with Nanocone Array

“…Organic photovoltaic (OPV) devices are promising candidates for clean renewable energy harvesting, which have attracted tremendous attention from many research groups due to their application for efficient flexible solar cells and high PCE over 17% for tandem design . In order to improve efficiency of OPV devices for commercial applications, a number of strategies can be employed, such as material development, interface and morphology optimization, or architectural engineering . Polymer semiconductors suffer from low mobilities and short diffusion lengths as compared to other types of semiconductors, which limits the active layer thickness and the light absorption.…”