Effects of Hydroiodic Acid Concentration on the Properties of CsPbI₃ Perovskite Solar Cells

Abstract

Inorganic cesium lead triiodide (CsPbI 3 ) perovskite materials are becoming increasingly attractive for use in perovskite/silicon tandem solar cells, due to their almost ideal band gap energy ( E g ) of about 1.7 eV. To be useful as photovoltaic absorbers, the CsPbI 3 must form the cubic or black phase (α-CsPbI 3 ). To do so at relatively low temperatures, hydroiodic acid (HI) is required as a solution additive. This paper demonstrates CsPbI 3 perovskite solar cells with an efficiency of 6.44%, formed using a HI concentration of 36 μL/mL. This value is higher than the previous most commonly used HI additive concentration. Herein, by undertaking a systematic study of the HI concentration, we demonstrate that the structural, morphological, optical, and electrical properties of CsPbI 3 solar cells, processed with this HI additive concentration, are superior.

Untapped Potentials of Inorganic Metal Halide Perovskite Solar Cells

“…38,86 Phase Stability The main challenge with the CsPbI 3 cell, which has been the focus of much research, is the phase instability due to transitions between the desirable photoactive perovskite black phase (a-CsPbI 3 , cubic Pm3m) and the undesirable non-perovskite yellow phase (d-CsPbI 3 , orthorhombic Pnma), although transition to the yellow phase is reversible. 42,[95][96][97] Yellow to black phase transition temperature ranges from 305 C to 360 C. 42,[95][96][97] A mixed phase of Pm3m and Pnma can also exist during transition between 290 C and 330 C. 97 Another complication, although also an advantage, is that the black phase can exist at a lower temperature, 96 allowing CsPbI 3 cells to be fabricated at around 100 C, 23,25,35,36,40,43,48,49,53 especially in the presence of hydroiodic acid (HI), 23,36,49,58,59 isopropanol (IPA), 25,40 sulfobetaine zwitterions, 47 or when bulky cations are incorporated. 43,48,49,51,59 Attempts to stabilize the black phase include (1) fast cooling, ''freezing,'' the meta-stable black state 96 ; (2) eliminating water, which plays a catalytic role in delaying yellow to black transition and expediting black to yellow transition 96 ; (3) using additive 23,25,36,40,47,…”

Ambient Air Stability of Hybrid Perovskite Thin‐Film Transistors by Ambient Air Processing

“…The robust electronegative polar groups of DMF, DMSO, and GBL (CO or SO) possess a Lewis base property, which enables them to coordinate with PbI 2 (Figure 1a). The solvent with a stronger Lewis base function presents a higher coordination ability with PbI 2 , and the coordination ability order for DMF, GBL, and DMSO is DMSO > DMF > GBL . The SO bond in DMSO has a higher electron cloud density than the CO bond in DMF, making DMSO a stronger Lewis base than DMF.…”

High‐Efficiency Nonfullerene Organic Solar Cells Enabled by Atomic Layer Deposited Zirconium‐Doped Zinc Oxide

“…EIS measurements mainly focus on testing the response of the device under an external alternating current (AC). [ 96,97 ] The applied voltage selected for both types of devices was selected as 0.7 V, which is slightly lower than their V oc . At a low voltage bias, traps in the active layer can respond to the modulated signal, whereas at a high voltage bias, the trap state can suppress the response.…”