Induced Crystallization of Perovskites by a Perylene Underlayer for High-Performance Solar Cells Zhao-Kui Wang,†,§ Xiu Gong,‡,§ Meng Li,† Yun Hu,† Jin-Miao Wang,† Heng Ma,‡ and Liang-Sheng Liao*,† †
Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China ‡ College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007, China S Supporting Information *
ABSTRACT: Perovskite crystallization and interface engineering are regarded as the most crucial factors in achieving high-performance planar heterojunction (PHJ) perovskite solar cells (PSCs). Herein, we demonstrate a thin perylene underlayer via a solution-processable method. By using branch-shaped perylene film as a seed-mediated underlayer, crystalline perovskites with fabric morphology can be formed, which allows for obvious improvement in absorption by a light scattering effect. With its deep highest occupied molecular orbital (HOMO) level, perylene also plays an important role in the energy-level tailoring of poly(3,4-ethylenedioxythiophene): poly(styrenesulphonate) (PEDOT:PSS) and CH3NH3PbIxCl3−x. In addition, perylene and perovskites form a fully crystalline heterojunction, which is beneficial for minimizing the defect and trap densities. Due to these merits, a maximum power conversion efficiency of 17.06% with improved cell stability is achieved. The finding in this work provides a simple route to control perovskite crystallizaition and to optimize the interfaces in PHJ PSCs simultaneously. KEYWORDS: perovskite solar cells, interface engineering, perylene underlayer, induced crystallization, stability
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2013 and referred to the concept of donor/acceptor in conventional organic solar cells.19 Noticeably, many conventional hole transport materials are difficult to apply in the p−i− n-type PHJ PSCs because the general solvents used for the perovskites, such as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), have very good solubility, which can wash off most of the underlayer of perovskites. Poly(3,4ethylenedioxythiophene): poly(styrenesulphonate) (PEDOT:PSS) is mostly employed as the p-type layer for hole extraction in p−i−n-type PHJ PSCs. However, the cell stability suffered from the acidic nature of the PEDOT:PSS dispersions.20,21 In addition, the low work function of PEDOT:PSS caused a relatively small open-circuit voltage (Voc) of around 0.90 V in these p−i−n-type PHJ PSCs.22,23 In addition to some inorganic HTLs, such as NiOx, CuO, and graphene oxide (GO),24−26 some organic HTLs,27−31 such as poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (poly-TPD) and poly(triaryl amine) (PTAA), which demon-
rganic−inorganic halide perovskite solar cells (PSCs) provide great potential for the photovoltaics industry due to their unique advantages, such as high efficiency.1−4 Nevertheless, PSCs are still in the early stages of commercialization compared with other mature solar cell technologies due to existing concerns such as the operational mechanism,5−7 lead toxicity,8−10 material stability,11,12 and interfacial engineering.13−15 Recently, planar heterojunction (PHJ) PSCs with controllable interface engineering demonstrated cell performance comparable to that of mesoscopic structure based PSCs.16−18 In typical PHJ PSCs, carrier behaviors of traveling through a transport pathway, including the perovskite active layer, the electron and hole transport layers (ETL and HTL, respectively), the electrodes, and the corresponding interfaces, can be manipulated effectively by choosing suitable interfacial layers. According to the layerstacking sequence, PHJ PSCs are divided into two groups: the conventional n−i−p structure in which the ETL is deposited on the bottom cathode and the p−i−n structure in which the HTL is deposited on the bottom anode. Particularly, the p−i−n configuration is regarded as more suitable for flexible devices because these devices can be fabricated at low temperature (
