Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

Abstract

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

Triggering the Passivation Effect of Potassium Doping in Mixed‐Cation Mixed‐Halide Perovskite by Light Illumination

“…As shown in Figure S4 in the Supporting Information, the compact shape and smooth surface of perovskite lamella Adv. [20] It is evidenced that light illumination can induce an improvement in photophysical properties of the 3.5 mol% K + perovskite, while in the 0 mol% K + perovskite light illumination leads to inferior PL behavior, which is intimately correlated with solar cell performance. 2019, 9,1901016 specific spatial distribution, tracing out the K/Br-rich grains.…”

“…[1][2][3][4] The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has rapidly progressed from 3.8% to exceed 24.2% during the past decade. [20] In this point of view, potassium cations are mainly distri buted at the surfaces and grain boundaries by forming KI/KBr to immobilize the surplus mobile halide ions and vacancies, [3] which is contradictory to the interstitial occupancy of K + in the perovskite lattice. Meanwhile, Abdi-Jalebi et al demonstrated that K + doping in mixed perovskites reduces nonradiative losses and photoinduced ion migration in perovskite films by decorating the surfaces and grain boundaries with passivating potassium halide layers.…”

Low-temperature, simple and efficient preparation of perovskite solar cells using Lewis bases urea and thiourea as additives: stimulating large grain growth and providing a PCE up to 18.8%

“…5,6 Theoretically speaking, it may produce a PCE of more than 30% with an improvement in ll factor (FF) and open circuit voltage (V oc ). [12][13][14] The incorporation of additive has been recognized as an efficient methodology to increase the performance of PSCs. [15][16][17][18] Previous reports have demonstrated that incorporating diiodooctane (DIO), NH 4 Cl 19,20 and alkylammonium iodides 11,21 can increase the performance of PSC devices.…”

Imaging and Mapping Characterization Tools for Perovskite Solar Cells

“…[88] Luo et al [88] implemented nano-XRF to show how Cs homogenized the A-site cation chemistry and how Cs + ions helped grain growth in a mixed perovskite (Figure 14A). [124,125] However, the mechanisms that drive these performance and long-term durability enhancements were not very well understood. [92] Third, K has been used to improve the long-term stability of PSCs.…”