Polymerization stabilized black-phase FAPbI3 perovskite solar cells retain 100% of initial efficiency over 100 days

Duan

et al. 2021

Small

Self Cite

attention due to their power conversion efficiency (PCE) rapidly exceeding 25.5% in a small area, which is comparable to the best Si solar cells. [2,3] The perovskite lightemitting diode (PeLED) also has above 20% electroluminescent (EL) external quantum efficiency (EQE EL ). [4][5][6] Their similar n-i-p heterostructure makes it possible to integrate photovoltaic/electroluminescent (PV/EL) functions in the same device, which is called PV/EL perovskite bifunctional diodes (PBDs). [7][8][9][10][11] PBDs are promising to open up applications of perovskites as colorful emitters, buildingintegrated PVs, and et al., thus are of significance for energy conservation and environmental protection. Besides, the PV and EL have a reciprocity relationship. [12] The EQE EL of a PV device is a valuable parameter for solar cell performance and can be used to evaluate the non-radiative recombination to the open-circuit voltage (V oc ) deficit based on reciprocity theorem by measuring the luminescence efficiency under forward bias. [13,14] The nonradiative recombination originates from the interfacial imperfection and the defects, which leads to the lower PCE and EQE EL . It is crucial to develop strategies to reduce the nonradiative recombination and minimize the V oc deficit.To realize efficient PSCs and PeLEDs, high-quality perovskite films with excellent crystallinity and low defect density are required to reduce energy loss. Among perovskite materials used in PSC, formamidinium-lead-iodide (FAPbI 3 )-based perovskites with tiny bromide anions, namely, (FAPbI 3 ) 1-x (MAPbBr 3 ) x where x is less than 0.05 (hereafter referred to as FAPbI 3 -based perovskites), possesses a close-to-ideal bandgap and acceptable stability. However, the FAPbI 3 -based PSC has great energy loss with a large V oc deficit. Improving the performance with the low nonradiative recombination of FAPbI 3 -based PSCs is therefore a major current research focus. To decrease bulk and interface defects, several strategies have been used, such as composition engineering, interface engineering, and surface passivation, and the detailed performance metrics shown in Table S1, Supporting Information. Composition engineering has shown a remarkable effective approach, such as using CsX, KX, and etc. for mixed perovskite. [15][16][17] In addition, the use of additives and defect passivation via surface functionalization in Integration of photovoltaic (PV) and electroluminescent (EL) functions and/or units in one device is attractive for new generation optoelectronic devices but it is challenging to achieve highly comprehensive efficiency. Herein, perovskite solar cells (PSCs) are fabricated, assisted by 3-sulfopropyl methacrylate potassium salt (SPM) additive to tackle this issue. SPMs not only induce large grain size during the film formation but also produce a secondary phase of 2D K 2 PbI 4 to passivate the grain boundaries (GBs). In addition, its sulfonic acid group and potassium ion can coordinate to lead ion and fill the interstitial defects, respectively. Thus...

Section: Improved Film Formation Assisted By Spmmentioning

confidence: 99%

Perovskite Bifunctional Diode with High Photovoltaic and Electroluminescent Performance by Holistic Defect Passivation

Duan

et al. 2021

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“…The presence of H

O in interstitial form in both the

and

phases of FAPI would better explain the enormous asymmetry between heating and cooling generally observed in the kinetics of the

transition, and particularly the range of characteristic times for the

transition at room temperature: from minutes to years, considering that in anhydrous or even low humidity conditions the

phase may be stable for several months [ 18 , 20 , 41 ]. Moreover, the temperature induced

transformation is seldom observed: a neutron diffraction experiment as a function of temperature at slow rate in a closed volume suggested that

K, but the permittivity curve no.…”

Section: Discussionmentioning

confidence: 99%

“…Other strategies for improving the stability are therefore based on additives that should passivate the grain boundaries or various types of encapsulation [ 13 ], but the improvements in stability are generally far from the requirements for commercial applications. Yet, it has been recently demonstrated that the addition of 2-(Dimethylamino)ethylmethacrylate to the solvent encapsulates each grain, making the

-FAPI film perfectly stable for at least 100 days in air [ 20 ], and considerable stability is obtained also by passivating the iodide vacancies with the addition of formate [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

Structural Transitions and Stability of FAPbI3 and MAPbI3: The Role of Interstitial Water

et al. 2021

We studied the influence of water on the structural stability and transformations of MAPI and FAPI by anelastic and dielectric spectroscopies under various temperature and H2O partial pressure protocols. Before discussing the new results in terms of interstitial water in MAPI and FAPI, the literature is briefly reviewed, in search of other studies and evidences on interstitial water in hybrid halide perovskites. In hydrated MAPI, the elastic anomaly between the cubic α and tetragonal β phases may be depressed by more than 50%, demonstrating that there are H2O molecules dispersed in the perovskite lattice in interstitial form, that hinder the long range tilting of the PbI6 octahedra. Instead, in FAPI, interstitial water accelerates in both senses the reconstructive transformations between 3D α and 1D δ phases, which is useful during the crystallization of the α phase. On the other hand, the interstitial H2O molecules increase the effective size of the MA and FA cations to which are bonded, shifting the thermodynamic equilibrium from the compact perovskite structure to the open δ and hydrated phases of loosely bonded chains of PbI6 octahedra. For this reason, when fabricating devices based on hybrid metal-organic halide perovskites, it is important to reduce the content of interstitial water as much as possible before encapsulation.

“…[ 11 ] Jen et al employed a large alkylammonium interlayer to reduce the defects and regulate the interfaces simultaneously, leading to a remarkable improvement of photovoltage from 1.12 to 1.21 V with a PCE over 22%. [ 12 ] In addition to the small molecule‐based passivators, long‐chain polymers such as poly(propylene carbonate), [ 13 ] poly(methyl methacrylate), [ 14 ] poly(ethylene oxide), [ 15 ] poly(2‐(dimethylamino) ethyl methacrylate), [ 16 ] and poly(bithiophene imide) [ 17 ] used as defect passivators have also been demonstrated to be effective in reducing defect densities. Regardless of the type of solid passivators reported previously, there is only one passivation process to heal the defects during the fabrication of perovskite films.…”

Section: Introductionmentioning

confidence: 99%

Azo‐Initiator‐Induced Cascade Defect Passivation for Efficient and Stable Planar Perovskite Solar Cells

Gao

Peng

et al. 2022

Solar RRL

Remarkable progress in perovskite solar cells (PSCs) has been made by virtue of surface and bulk modification for defect control of perovskite layers, however, the interior defects in the perovskite layer can be hardly passivated by means of conventional passivation strategies, which makes perovskites prone to decomposition with inferior device performance. Here, the authors propose a cascade defect passivation strategy to doubly reduce perovskite defects by introducing a series of azo radical initiators. The primary passivation process of the azo compounds is realized on the perovskite surfaces through strong coordination interactions between Pb2+ and carbonyl/cyano groups. The secondary passivation occurs after thermal treatment, and the decomposed products diffuse into the interior defects of the initial passivated perovskite films through grain boundaries to accomplish the cascade defect passivation. Excitingly, this passivation strategy inhibits unwanted defect‐assisted recombination effectively, and thus CH3NH3PbI3 (MAPbI3)‐based inverted PSCs exhibit a significant increase in power conversion efficiency (PCE) from 16.92% to 19.69%. Moreover, the dual‐passivated PSCs show only 10% PCE loss after 3000 h in an inert atmosphere. Overall, the first proposed cascade defect passivation strategy is highly efficient in promoting defect healing of perovskites, demonstrating a new way to prepare high‐quality perovskite films for high‐performance PSCs.