Efficient Perovskite Solar Cells by Reducing Interface‐Mediated Recombination: a Bulky Amine Approach

Abstract

meantime, the ease of the solution process at low temperature renders this technology up-and-coming for large-scale low-cost manufacture. However, these solution-processed perovskite films are usually polycrystalline, which readily form defects at the grain boundaries and on the surface of the films. [1][2][3][4][5][6] Such defects are the center of non-radiative recombination of photo-generated electrons and holes, which causes shorter carrier lifetime and lower open-circuit voltage (V OC ). Hence, in real devices, higher recombination rate occurs close to the interface of the sequentially deposited layers. For typical n-i-p perovskite solar cells (PSCs), the perovskite/hole transport layer (HTL) interface holds the high defect density, such as cation/anion vacancy and dangling bonds, etc., [7,8] resulting in defect-assisted recombination. Additionally, the energy level mis-alignment near the interface due to quasi-fermi level pinning will increase recombination velocity [9] and the recombination loss occurs inevitably across interfaces between holes in HTL and minority carriers (electron) in the perovskite, or HTL themselves. [10,11] These existing recombination loss channels at the surface/ interface of the perovskite will severely limit the V OC and overall efficiency of PSCs.Many studies have demonstrated that passivation is an efficient method to lessen the non-radiative recombination loss at the surface/interface of the perovskite in n-i-p PSCs. For example, excess PbI 2 [4,[12][13][14] was believed to passivate the grain boundaries and interface of electron transport layer with perovskite; conjugated polymers [15] and insulating poly(methyl methacrylate) [16,17] were also used to passivate the interface of perovskite/HTL. Recently, various ammonium halide compounds, [8,18,19] especially bulky organic ammonium halide salts were adopted to passivate the surface of perovskite, such as 1,8-octanediammonium iodide, [3] adamantylammonium hydroiodide, [7] (fluorine-)phenylethylammonium iodide (F-)PEAI, [20][21][22][23] n-hexyl trimethyl ammonium bromide, [24] etc. They could interact with the undercoordinated ions or form low-dimensional perovskite phases to passivate the surface/ interface of bulk perovskite. The stability of devices was also usually improved due to the suppression of ionic migration by the packed organic moiety or the formation of hydrophobic low-dimensional perovskites. [7,23,25] A very recent work by Jiang et al. found exceptionally that the insulating PEAI salt, rather than the 2D layered PEA 2 PbI 4 perovskite, served as a moreThe presence of non-radiative recombination at the perovskite surface/ interface limits the overall efficiency of perovskite solar cells (PSCs). Surface passivation has been demonstrated as an efficient strategy to suppress such recombination in Si cells. Here, 1-naphthylmethylamine iodide (NMAI) is judiciously selected to passivate the surface of the perovskite film. In contrast to the popular phenylethylammonium iodide, NMAI post-treatment primarily leaves NMAI sal...

Donor–π–Acceptor Type Porphyrin Derivatives Assisted Defect Passivation for Efficient Hybrid Perovskite Solar Cells

“…[ 8–12 ] In order to further improve the stability and efficiency of PSCs, it is necessary to select appropriate passivators to modify the interface of the PVSK layer. [ 13–16 ] In the past few years, numerous studies have demonstrated that functional groups, such as pyridine, thiophene, iodopentafluorobenzene, [ 17 ] cyano, [ 18 ] sulfonate (OSO 3 − ), [ 19 ] fluorine, carboxylic acid could act as the passivator of defects in perovskite film, for example, under‐coordinated Pb 2+ cations, and hence reduce the nonradiative charge recombination. [ 20,21 ]…”

The Impact of PbI2:KI Alloys on the Performance of Sequentially Deposited Perovskite Solar Cells

“…The Nyquist plots obtained from EIS measurement at a bias of 0.8 V exhibit two semicircles, as shown in Figure 6b. According to the equivalent circuit model (inset), R rec is the sum of the resistance of the first semicircle at high frequency and the second semicircle at low frequency [73,74] . Obviously, the diameters of two semicircles of the K5 device are larger than that of the Control device, indicating larger R rec and reduced interface non‐radiative recombination.…”

Insights into the effect of bromine‐based organic salts on the efficiency and stability of wide bandgap perovskite

“…According to group II , the surface morphology of perovskite films tested by high temperature environment changed compared with group I , and many white particles appeared on the surface, which has been proved to be PbI 2 . [ 33 ] The MABr and GABr films, on the other hand, seemed to show better crystal quality and smoother film surfaces. XRD results are consistent with the SEM, indicating that surface passivation of MABr and GABr can improve the thermal stability of perovskite films.…”