Perovskite solar cells contain various defects within the perovskite absorber and the corresponding interfaces, affecting device performance and stability. Fortunately, there have been tremendous efforts in advancing passivation techniques contributing to high‐efficiency devices with improved stability. Here, the state‐of‐the‐art passivation approaches for each layer of the perovskite cell with the aim of improving carrier extraction, reducing carrier recombination and improving cell stability and performance are reviewed.
Perovskite solar cells contain various defects within the perovskite absorber and the corresponding interfaces, affecting device performance and stability. Fortunately, there have been tremendous efforts in advancing passivation techniques contributing to high‐efficiency perovskite solar cell with improved stability. Here, the state‐of‐the‐art passivation approaches for each layer of the perovskite cell with the aim of improving carrier extraction, reducing carrier recombination, and/or improving cell stability are reviewed. Passivation of the electron transport layer can improve the stability of perovskite solar cells by reducing trap states or by physically separating the transport layer from contacting perovskite. Controlling the amount of PbI2 in the perovskite precursor has been found to be effective in passivating defect states at the grain boundaries and on the surface. Additives such as elemental iodine, organic surfactants, and Group 1 metal compounds incorporated in perovskite precursors have been reported to passivate recombination trap centers. These approaches have also contributed to improved energy band alignment between carrier transport layers and perovskite absorber improving device performance. An effective strategy to improve moisture stability is the use of 2D perovskites or hydrophobic large cation molecules forming 2D or quasi‐2D phases at grain boundaries or film surfaces providing passivation and preventing moisture ingress.
by Xiaoming Li,
Gongyue Huang,
Nan Zheng,
Yonghai Li,
Xiao Kang,
Shanlin Qiao,
Huanxiang Jiang,
Weichao Chen,
Renqiang Yang
A novel phenyl substituted benzo(1,2‐b:4,5‐b’)dithiophene (BDT) derivative containing both fluorine and sulfur atoms is designed and synthesized. A power conversion efficiency of 13.91% is achieved with a high open‐circuit voltage of 1.01 V, and a large short‐circuit current density of 18.51 mA cm−2. The result demonstrates that PBTA‐PSF is a promising candidate for high‐performance donor polymers.
A novel phenyl substituted benzo(1,2‐b:4,5‐b’)dithiophene (BDT) derivative containing both fluorine and sulfur atoms is designed and synthesized. Furthermore, a wide bandgap polymer PBTA‐PSF based on the derivative shows a low highest occupied molecular orbital energy level and slightly reduces the donor materials’ optical bandgap, which has a complementary absorption with a narrow‐bandgap n‐type small molecule ITIC. As a result, a power conversion efficiency of 13.91% is achieved with a high open‐circuit voltage of 1.01 V, and a large short‐circuit current density of 18.51 mA cm−2. The result demonstrates that PBTA‐PSF is a promising candidate for high‐performance donor and phenyl‐containing BDT derivatives and has potential in the design of high‐performance polymers for organic photovoltaics.
by Xingtian Yin,
Yuxiao Guo,
Haixia Xie,
Wenxiu Que,
Ling Bing Kong
Nickel oxide based perovskite solar cells are reviewed comprehensively in the present paper. Particularly, the fabrication method for NiOx films, surface modification, and doping strategies are discussed in detail with special attention paid to the relationship between the optoelectronic properties of NiOx films and the performance of resulting perovskite solar cell devices.
Organic–inorganic halide perovskite solar cells (PSCs) have achieved great success in recent years with a demonstrated power conversion efficiency (PCE) increasing rapidly from 3.8% to 22.3% for single junction devices. Most high‐performance PSCs consist of a perovskite absorber sandwiched between an electron transport layer (ETL) and a hole transport layer (HTL), which extracts electrons (holes) and blocks holes (electrons) from the absorber efficiently. Inorganic hole transport materials have extracted extensive attention due to their higher mobility and better stability. Particularly, the excellent hole selective transport property of nickel oxide (NiOx) has been highlighted by its recent application in organometallic halide PSCs, due to the favorable band alignment formed between the halide perovskite absorber and NiOx HTL. This comprehensive review summarizes the recent progress in the fabrication of NiOx films and their application in PSCs. Special attention is paid to the optoelectronic properties of NiOx films, which strongly depend on the synthesis methods and post‐treatment conditions, as well as the resulting photovoltaic device performance. Surface modification and doping strategies that are used to improve the optoelectronic properties of NiOx films and the resulting device performance are discussed with emphasis. Finally, a short perspective of NiOx‐based PSCs is also provided.
Impacts of alkaline on the defects property and crystallization kinetics in perovskite solar cells
Impacts of alkaline on the defects property and crystallization kinetics in perovskite solar cells, Published online: 07 March 2019; doi:10.1038/s41467-019-09093-1
Defect density reduction is pertinent for halide perovskite solar cells but a universal strategy has not been exploited. Here Chen et al. show that by fine tuning the alkaline environment in precursor solution, they can greatly suppress defects density and obtain high certified efficiency of 20.87%.
Energy Environ. Sci., 2019, 12,1495-1511 DOI: 10.1039/C8EE03559H, Review Article
Yuanyuan Zhou, Yixin Zhao Insights into the chemical stability and instability of inorganic halide perovskites are provided. The content of this RSS Feed (c) The Royal Society of Chemistry
by Xianqiang Li,
Wenhui Li,
Yijie Yang,
Xue Lai,
Qiang Su,
Dan Wu,
Gongqiang Li,
Kai Wang,
Shuming Chen,
Xiao Wei Sun,
Aung Ko Ko Kyaw
A dithienobenzodithiophene‐based π‐conjugated polymer with fluorinated benzotriazole is applied through an anti‐solvent process to passivate the defects of the perovskite film. The fluorinated polymer interacts with undercoordinated Pb2+ ions to form a Pb‐F bond in the perovskite crystals, resulting in a reduced trap density, fast charge transfer, and enhanced performance and stability of the perovskite solar cell.
A dithienobenzodithiophene‐based π‐conjugated polymer consisting of fluorinated benzotriazole and benzothiadiazole is successfully applied through anti‐solvent method to passivate the defects of perovskite crystals. The fluorinated polymer interacts with under coordinated Pb2+ ions in the perovskite crystals to form Pb‐F bond which effectively passivates the defects. The trap density is reduced and the charge carrier transfer between the perovskite film and Spiro‐OMeTAD is also improved after passivation with the polymer. As a result, a power conversion efficiency (PCE) of 18.03% is achieved in the champion cell. After storing in an ambient environment with 60% relative humidity for 1000 h, the device still retains 90% of the original PCE. These results demonstrate that dithienobenzodithiophene‐based π‐conjugated polymers are promising materials for passivation of perovskite films to further improve the performance and stability of perovskite solar cells.
by Wu, W.-Q., Yang, Z., Rudd, P. N., Shao, Y., Dai, X., Wei, H., Zhao, J., Fang, Y., Wang, Q., Liu, Y., Deng, Y., Xiao, X., Feng, Y., Huang, J.
The power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) are already higher than that of other thin film technologies, but laboratory cell-fabrication methods are not scalable. Here, we report an additive strategy to enhance the efficiency and stability of PSCs made by scalable blading. Blade-coated PSCs incorporating bilateral alkylamine (BAA) additives achieve PCEs of 21.5 (aperture, 0.08 cm2) and 20.0% (aperture, 1.1 cm2), with a record-small open-circuit voltage deficit of 0.35 V under AM1.5G illumination. The stabilized PCE reaches 22.6% under 0.3 sun. Anchoring monolayer bilateral amino groups passivates the defects at the perovskite surface and enhances perovskite stability by exposing the linking hydrophobic alkyl chain. Grain boundaries are reinforced by BAA and are more resistant to mechanical bending and electron beam damage. BAA improves the device shelf lifetime to >1000 hours and operation stability to >500 hours under light, with 90% of the initial efficiency retained.
While hybrid perovskites have great potential as light-absorbing materials, they suffer from moisture-induced instability. Herein, we added the amino acid iodide salt-based molecular crosslinker p-aminobenzoic acid (PABA∙HI) to a perovskite precursor solution to enhance the humidity stability. The rigid molecular structure of PABA∙HI played an important role in determining the crystal orientation, trap density, and photovoltaic performance of the perovskite solar cells (PVSCs). PABA∙HI can effectively interact with the Pb-I framework via hydrogen bonds, enhancing the crosslinking efficiency compared with freely rotating flexible molecular crosslinkers. Kelvin probe force microscopy in conjunction with Raman analysis confirmed the presence of PABA∙HI at the grain boundaries; thus, stable quasi-two-dimensional perovskite existed along the grain boundaries, passivating the grain boundaries and improving the moisture stability. The PABA∙HI-added PVSCs having a power-conversion efficiency (PCE) of 17.4% retained 91% of their initial PCE when stored for 312 h at a relative humidity of 75% at 25 °C, whereas a pristine cell with a PCE of 16.4% only retained 37% of its initial value. Our findings clearly indicate that the amino acid salt as a rigid molecular crosslinker improved not only the photovoltaic performance but also the stability against moisture.
Graphical abstract
The addition of rigid molecular crosslinker p-aminobenzoic acid iodide (PABA∙HI) enhanced the stability of perovskites against moisture by forming quasi-two-dimensional perovskite along grain boundaries. Perovskite solar cells with PABA∙HI retained 91% of their initial power-conversion efficiency of 17.4% under a relative humidity of 75% at 25 °C after 312 h of exposure under dark condition.
The quality of perovskite absorber is one of the most important factors to influence the efficiency and stability of perovskite solar cells (PSCs). However, it is still challenging to obtain perovskite layers with required properties including large grain sizes, better crystallinity, less grain boundaries, and uniform morphology by the current preparation techniques. Here we develop a novel method, where the CsPbBr3 nanoparticles (NPs) are introduced into the chlorobenzene anti-solvent to improve the MAPbI3 film quality in terms of film structure, morphology and crystallinity, leading to reduced charge recombination and improved charge transfer. CsPbBr3 NPs play a role as nucleation centers in the growth process of perovskite films, and CsPbBr3 NPs also induce a passivation layer Cs1-yMAyPbI3-xBrx on the top of perovskite layer. The charge transport and power conversion efficiency (PCE) are improved due to the introduction of CsPbBr3 NPs. A champion PCE of 20.46% is obtained for the PSCs based on high quality perovskite film prepared with CsPbBr3 NPs. In addition, the PSCs with CsPbBr3 NPs also exhibit improved stability. This work not only demonstrates a novel strategy to prepare high quality perovskite films for PSCs with high efficiency and stability, but also provides important insight in the growth mechanisms of perovskite films toward high crystallinity and less defects.
Graphical abstract
In this work, the CsPbBr3 NPs are used to serve as nucleation centers to improve the quality of the perovskite films. In addition, the introduction of CsPbBr3 NPs also leads to the formation of Cs1-yMAyPbI3-xBrx between MAPbI3 layer and the hole transporting layer. The optimized device exhibits an PCE of 20.46% and excellent long-term stability (90% of initial PCE remains after 500 h).
by Yuliar Firdaus,
Vincent M. Le Corre,
Jafar I. Khan,
Zhipeng Kan,
Frédéric Laquai,
Pierre M. Beaujuge,
Thomas D. Anthopoulos
The efficiency limits in non‐fullerene organic solar cells are examined using a numerical simulator. Power conversion efficiency (PCE) of over 18% using recently reported carrier mobility values and voltage losses, are predicted. Increasing the mobility to >10−3 cm2 V−1 s−1 and decreasing the recombination constant to <10−12 cm3 s−1 is shown to yield a single‐junction and 2T‐tandem cell with PCEs of >20% and >25%, respectively.
Abstract
The reported power conversion efficiencies (PCEs) of nonfullerene acceptor (NFA) based organic photovoltaics (OPVs) now exceed 14% and 17% for single‐junction and two‐terminal tandem cells, respectively. However, increasing the PCE further requires an improved understanding of the factors limiting the device efficiency. Here, the efficiency limits of single‐junction and two‐terminal tandem NFA‐based OPV cells are examined with the aid of a numerical device simulator that takes into account the optical properties of the active material(s), charge recombination effects, and the hole and electron mobilities in the active layer of the device. The simulations reveal that single‐junction NFA OPVs can potentially reach PCE values in excess of 18% with mobility values readily achievable in existing material systems. Furthermore, it is found that balanced electron and hole mobilities of >10−3 cm2 V−1 s−1 in combination with low nongeminate recombination rate constants of 10−12 cm3 s−1 could lead to PCE values in excess of 20% and 25% for single‐junction and two‐terminal tandem OPV cells, respectively. This analysis provides the first tangible description of the practical performance targets and useful design rules for single‐junction and tandem OPVs based on NFA materials, emphasizing the need for developing new material systems that combine these desired characteristics.
The molecular orientation and charge extraction of PEDOT:PSS‐based hole‐transporting layers are effectively modulated through fine tuning of the surface energy by introducing poly(styrene sulfonic acid) sodium salts or nickel formate dihydrate, which boosts the fill factor and eventual efficiency of organic solar cells based on fullerene and nonfullerene acceptors.
Abstract
Interface properties are of critical importance for high‐performance bulk‐heterojunction (BHJ) organic solar cells (OSCs). Here, a universal interface approach to tune the surface free energy (γS) of hole‐transporting layers (HTLs) in a wide range through introducing poly(styrene sulfonic acid) sodium salts or nickel formate dihydrate into poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is reported. Based on the optimal γS of HTLs and thus improved face‐on molecular ordering in BHJs, enhanced fill factor and power conversion efficiencies in both fullerene and nonfullerene OSCs are achieved, which is attributed to the increased charge carrier mobility and sweepout with reduced recombination. It is found that the face‐on orientation‐preferred BHJs (PBDB‐TF:PC71BM, PBDB‐T:PC71BM, and PBDB‐TF:IT‐4F) favor HTLs with higher γS while the edge‐on orientation‐preferred BHJs (PDCDT:PC71BM, P3HT:PC71BM and PDCBT:ITIC) are partial to HTLs with lower γS. Based on the surface property–morphology–device performance correlations, a suggestion to select a suitable HTL in terms of γS for a specific BHJ with favored molecular arrangement is provided. This work enriches the fundamental understandings on the interface characteristics and morphological control toward high‐efficiency OSCs based on a wide range of BHJ materials.
J. Mater. Chem. A, 2019, 7,9025-9033 DOI: 10.1039/C9TA01760G, Paper
Jin-Feng Liao, Wu-Qiang Wu, Jun-Xing Zhong, Yong Jiang, Lianzhou Wang, Dai-Bin Kuang A multifunctional 2D polymeric semiconductor was incorporated to provide surprisingly robust efficacy in grain boundary functionalization and defect passivation of perovskite, which suppresses charge recombination and thus affording an illustrious photovoltage of 1.16 V and power conversion efficiency of 21.1%. The content of this RSS Feed (c) The Royal Society of Chemistry
Inorganic halide perovskite CsPbI2Br has attracted tremendous attentions in the photovoltaic fields in view of its improved ambient phase stability and reasonable band gap (1.91eV). Traditional one-step solution-processed CsPbI2Br absorbers, however, usually suffer from poor morphology, low crystallinity and thin thickness, which impede further promotion of device performance. Herein, an anti-solvent assisted multi-step deposition strategy for high-quality CsPbI2Br film is demonstrated, wherein different anti-solvents are first introduced in the PbI2 precursor filming processes to construct porous PbI2(DMSO) films. Then CsBr solution intercalates into the porous PbI2(DMSO) film by multi-step deposition, effectively facilitating the close contact of reactants and complete annealing reaction. CsBr drops and porosity degree of PbI2(DMSO) film are found to control the final morphology and phase composition of the perovskite film. Utilizing green ethanol (EtOH) treated PbI2 film with high porosity and randomized orientation, highly pure-phase and full-coverage CsPbI2Br films with high thickness, large grain sizes and high crystallinity are obtained after optimizing CsBr drops. Finally, carbon-based all-inorganic planar perovskite solar cells (PSCs) with absorbers prepared through above methods achieve a champion efficiency of 10.21%, which is a record value for the CsPbI2Br PSCs without hole transport layer. More importantly, the unencapsulated all-inorganic CsPbI2Br device shows a promising long-term stability with no obvious efficiency degradation when exposed in ambient atmosphere with 15–30% relative humidity (RH) at room temperature for 44 days.
J. Mater. Chem. A, 2019, 7,8889-8896 DOI: 10.1039/C8TA12530A, Paper
Miao Li, Yuanyuan Zhou, Jianqi Zhang, Jinsheng Song, Zhishan Bo Fused-ring electron acceptors with asymmetric terminals for highly efficient thick-film photovoltaic devices. The content of this RSS Feed (c) The Royal Society of Chemistry
by Jingru Zhang,
Gary Hodes,
Zhiwen Jin,
Shengzhong Liu
Recently, lead halide‐based perovskites have become one of the hottest topics in photovoltaic research due to their excellent optoelectronic properties. Among them, organic‐inorganic hybrid perovskite solar cells (PSCs) have made very rapid progress with their power conversion efficiency (PCE) now at 23.7%. However the intrinsically unstable nature of these materials, particularly to moisture and heat, may be a problem for their long‐term stability. Replacing the fragile organic group with more robust inorganic Cs+ cations forms the cesium lead halide system (CsPbX3, X is halide) as all‐inorganic perovskites which are much more thermally stable and often more stable to other factors. From the first report in 2015 to now, the PCE of CsPbX3‐based PSCs has abruptly increased from 2.9% to 17.1% with much enhanced stability. In this review, we aim to summarize the field up to now, propose solutions in terms of development bottlenecks, and attempt to boost further research in CsPbX3 PSCs. After a general introduction, we discuss the various CsPbX¬3 materials and cells beginning with CsPbI3, followed by CsPbBr3 and then the mixed halide CsPb(I,Br)3 materials and cells. Finally, challenges and perspectives for the future development of CsPbX3 PSCs are presented.
by Guoqing Tong,
Taotao Chen,
Huan Li,
Wentao Song,
Yajing Chang,
Jingjing Liu,
Linwei Yu,
Jun Xu,
Yabing Qi,
Yang Jiang
All‐bromide perovskite solar cells with gradient bandgap are constructed by vapor deposition procedure accompanying with the derivative‐phase to boost the hole extraction efficiency and stability. An impressive power conversion efficiency of 10.17% is obtained via a vapor deposition method for a hole transfer layer‐free inorganic PSC. The device also exhibits an excellent humidity and thermal stability for more than 3000 h in RH ≈45% environment and 700 h at 100 °C. These results pave a great advancement in all inorganic PSCs and also open the window of perovskite derivative‐phase.
Inorganic perovskite materials have demonstrated outstanding performance in the field of photovoltaic devices due to their superior charge carrier transport properties and excellent thermal stability. In particular, the inorganic perovskite derivative phases show special properties in terms of phase stability and optoelectronic application, especially in the phase transition investigation. However, their commercial applications still face challenges due to the large recombination at the interface, resulting in poor efficiency and metastable phases such as iodide perovskite existing in the film. Herein, an all‐bromide inorganic perovskite solar cell has been developed by introducing the derivative phases (CsPb2Br5 and Cs4PbBr6) to construct gradient bandgap architecture. This graded heterojunction device is realized with a controllable sequential vapor deposition procedure. The valance band maximum elevates gradually with the presence of derivative phases and effectively blocks electrons and boosts the hole extraction efficiency at the counter electrode, which promotes charge separation and reduces the interface recombination. Ultimately, an impressive power conversion efficiency of 10.17% is achieved through a CsPbBr3/CsPbBr3‐CsPb2Br5/CsPbBr3‐Cs4PbBr6 architecture strategy with excellent stability above 3000 h (85% of initial performance) in a humid environment (@RH ≈45%) and 700 h (83% of initial efficiency) under thermal conditions (@ 100 °C).
Multijunction organic solar cells provide higher power conversion efficiencies than the corresponding single junction solar cells by reducing thermalization and transmission losses and are fabricated by sequential layer deposition from solution. In recent years, important progress has been made in terms of novel materials and device design and the most salient advances are discussed.
Abstract
The efficiency of organic solar cells can benefit from multijunction device architectures, in which energy losses are substantially reduced. Herein, recent developments in the field of solution‐processed multijunction organic solar cells are described. Recently, various strategies have been investigated and implemented to improve the performance of these devices. Next to developing new materials and processing methods for the photoactive and interconnecting layers, specific layers or stacks are designed to increase light absorption and improve the photocurrent by utilizing optical interference effects. These activities have resulted in power conversion efficiencies that approach those of modern thin film photovoltaic technologies. Multijunction cells require more elaborate and intricate characterization procedures to establish their efficiency correctly and a critical view on the results and new insights in this matter are discussed. Application of multijunction cells in photoelectrochemical water splitting and upscaling toward a commercial technology is briefly addressed.
A perovskite solar cell with both high efficiency and high thermal stability is examined. The optimized device achieved by engineering perovskite composition exhibits 92% power conversion efficiency retention in a stress test conducted at 85 °C/85% RH while exceeding 20% power conversion efficiency (certified efficiency of 20.8% at 1 cm2). These results reveal a great potential for future practical use.
Abstract
Perovskite solar cells have received great attention because of their rapid progress in efficiency, with a present certified highest efficiency of 23.3%. Achieving both high efficiency and high thermal stability is one of the biggest challenges currently limiting perovskite solar cells because devices displaying stability at high temperature frequently suffer from a marked decrease of efficiency. In this report, the relationship between perovskite composition and device thermal stability is examined. It is revealed that Rb can suppress the growth of PbI2 even under PbI2‐rich conditions and decreasing the Br ratio in the perovskite absorber layer can prevent the generation of unwanted RbBr‐based aggregations. The optimized device achieved by engineering perovskite composition exhibits 92% power conversion efficiency retention in a stress test conducted at 85 °C/85% relative humidity (RH) according to an international standard (IEC 61215) while exceeding 20% power conversion efficiency (certified efficiency of 20.8% at 1 cm2). These results reveal the great potential for the practical use of perovskite solar cells in the near future.
by Zhihui Liao,
Yuanpeng Xie,
Lie Chen,
Yun Tan,
Shaorong Huang,
Yongkang An,
Hwa Sook Ryu,
Xiangchuan Meng,
Xunfan Liao,
Bin Huang,
Qian Xie,
Han Young Woo,
Yanming Sun,
Yiwang Chen
Three polymers L24, L68, and L810 are developed as donor materials for organic solar cells. As the alkyl side chain of the fluorobenzotriazole (FTAZ) unit increases, the L810‐based device exhibits lower energy loss, better molecular face‐on orientation, and a higher absorption coefficient. Consequently, the power conversion efficiency is improved to 12.1%, which is one of the highest values for FTAZ‐based devices.
Abstract
The fluorobenzotriazole (FTAZ)‐based copolymer donors are promising candidates for nonfullerene polymer solar cells (PSCs), but suffer from relatively low photovoltaic performance due to their unsuitable energy levels and unfavorable morphology. Herein, three polymer donors, L24, L68, and L810, based on a chlorinated‐thienyl benzodithiophene (BDT‐2Cl) unit and FTAZ with different branched alkyl side chain, are synthesized. Incorporation of a chlorine (Cl) atom into the BDT unit is found to distinctly optimize the molecular planarity, energy levels, and improve the polymerization activity. Impressively, subtle side chain length of FTAZ realizes a dramatic improvement in all the device parameters, as revealed by the short‐current density (Jsc) improved from 7.41 to 20.76 mA cm−2, fill‐factor from 36.3 to 73.5%, and even the open‐circuit voltage (Voc) from 0.495 to 0.790 V. The best power conversion efficiency (PCE) of 12.1% is obtained from the L810‐based device, which is one of the highest values reported for FTAZ‐based PSCs so far. Notably, the corresponding external quantum efficiency curve keeps a very prominent value up to 80% from 500 to 800 nm. The notable performance is discovered from the reduced energy loss, improved molecular face‐on orientation, the down‐shifted energy levels, and optimized absorption coefficient regulated by side‐chain engineering.
J. Mater. Chem. A, 2019, 7,8690-8699 DOI: 10.1039/C9TA01364D, Review Article
Fanning Meng, Anmin Liu, Liguo Gao, Junmei Cao, Yeling Yan, Ning Wang, Meiqiang Fan, Guoying Wei, Tingli Ma Low cost carbon paste using as the back electrode for perovskite solar cells (PSCs), interfacial engineering plays a crucial role in both bi-interfacial structure and tri-interfacial structure. The content of this RSS Feed (c) The Royal Society of Chemistry
by Haoxuan Sun,
Yu Zhou,
Yu Xin,
Kaimo Deng,
Linxing Meng,
Jie Xiong,
Liang Li
Highly efficient SnO2 ETL for planar perovskite solar cells is produced by using a plasma treatment procedure. This procedure enables the precise control of composition, defects, and band energy levels at the interface between FTO and perovskite. This simple and efficient source‐free fabrication technology provides a versatile platform for the manufacture of PSCs.
Abstract
Perovskite solar cells (PSCs) have received much attention and with them a power conversion efficiency (PCE) of over 22% has been achieved. Electron transport layers (ETLs) based on metal oxide materials play an important role in transferring electrons and reducing back recombination. However, existing fabrication approaches are generally waste too many materials and consume too much energy for commercial application. Here, a brand new plasma preannealing procedure is proposed that can replace the traditional ETL preparation process and alleviate the above‐mentioned problems. A pure SnO2 phase in situ formed on the fluorine‐doped tin oxide (FTO) surface can be obtained at room temperature by only 15 min oxygen plasma assisted reaction without postheating treatment. It enables the precise control of compositions, defects, and energy levels of band at the surface of FTO substrate, resulting in a prominent PCE of 20.39% with excellent stability and reproducibility. This simple and efficient source‐free fabrication technology provides a versatile platform for the manufacture of PSCs in the future.
Energy Environ. Sci., 2019, 12,1413-1425 DOI: 10.1039/C9EE00311H, Paper
Artem Musiienko, Pavel Moravec, Roman Grill, Petr Praus, Igor Vasylchenko, Jakub Pekarek, Jeremy Tisdale, Katarina Ridzonova, Eduard Belas, Lucie Landová, Bin Hu, Eric Lukosi, Mahshid Ahmadi Understanding the type, formation energy and capture cross section of defects is one of the challenges in the field of organometallic halide perovskite (OMHP) devices. The content of this RSS Feed (c) The Royal Society of Chemistry
by Luana Mazzarella,
Yen‐Hung Lin,
Simon Kirner,
Anna B. Morales‐Vilches,
Lars Korte,
Steve Albrecht,
Ed Crossland,
Bernd Stannowski,
Chris Case,
Henry J. Snaith,
Rutger Schlatmann
The optical absorption in monolithic perovskite/silicon tandem solar cells with flat Si front‐side is improved. The successful tailoring and incorporation of a nanocrystalline silicon oxide composite interlayer with tuneable refractive index is demonstrated on device by experiments and optical simulations. Improved short‐circuit current density (38.7 mA cm−2) combined with excellent contact properties lead to a cell with a certified stabilized conversion efficiency of 25.2%.
Abstract
Perovskite/silicon tandem solar cells are attractive for their potential for boosting cell efficiency beyond the crystalline silicon (Si) single‐junction limit. However, the relatively large optical refractive index of Si, in comparison to that of transparent conducting oxides and perovskite absorber layers, results in significant reflection losses at the internal junction between the cells in monolithic (two‐terminal) devices. Therefore, light management is crucial to improve photocurrent absorption in the Si bottom cell. Here it is shown that the infrared reflection losses in tandem cells processed on a flat silicon substrate can be significantly reduced by using an optical interlayer consisting of nanocrystalline silicon oxide. It is demonstrated that 110 nm thick interlayers with a refractive index of 2.6 (at 800 nm) result in 1.4 mA cm−² current gain in the silicon bottom cell. Under AM1.5G irradiation, the champion 1 cm2 perovskite/silicon monolithic tandem cell exhibits a top cell + bottom cell total current density of 38.7 mA cm−2 and a certified stabilized power conversion efficiency of 25.2%.
by Hanul Min,
Gwisu Kim,
Min Jae Paik,
Seungwoon Lee,
Woon Seok Yang,
Minsu Jung,
Sang Il Seok
The elemental sulfur (S8) added to the perovskite precursor solution ((FAPbI3)0.95(MAPbBr3)0.05 in dimethylformamide/dimethyl sulfoxide) not only increases the stability of the solution owing to amine–sulfur coordination but also significantly improves the thermalstability and photostability due to the increase in chemical stability of the perovskite material itself without compromising the power conversion efficiency of the resulting perovskite solar cells.
Abstract
Efficient perovskite solar cells (PSCs) are mainly fabricated by a solution coating processes. However, the efficiency of such devices varies significantly with the aging time of the precursor solution used to fabricate them, which includes a mixture of perovskite components, especially methylammonium (MA), and formamidinium (FA) cations. Herein, how the inorganic–organic hybrid perovskite precursor solution of (FAPbI3)0.95(MAPbBr3)0.05 degrades over time and how such degradation can be effectively inhibited is reported on, and the associated mechanism of degradation is discussed. Such degradation of the precursor solution is closely related to the loss of MA cations dissolved in the FA solution through the deprotonation of MA to volatile methylamine (CH3NH2). Addition of elemental sulfur (S8) drastically stabilizes the precursor solution owing to amine–sulfur coordination, without compromising the power conversion efficiency (PCE) of the derived PSCs. Furthermore, sulfur introduced to stabilize the precursor solution results in improved PSC stability.
by James Bullock,
Yimao Wan,
Mark Hettick,
Xu Zhaoran,
Sieu Pheng Phang,
Di Yan,
Hanchen Wang,
Wenbo Ji,
Chris Samundsett,
Ziv Hameiri,
Daniel Macdonald,
Andres Cuevas,
Ali Javey
An electron‐selective TiOx based heterocontact is developed and trialed as a dopant‐free partial rear contact in high efficiency silicon solar cells. This cell not only reaches an efficiency of above 23% but also maintains its performance after a short anneal at 400 °C—setting new benchmarks of performance and thermal stability for this cell architecture.
Abstract
Over the past five years, there has been a significant increase in both the intensity of research and the performance of crystalline silicon devices which utilize metal compounds to form carrier‐selective heterocontacts. Such heterocontacts are less fundamentally limited and have the potential for lower costs compared to the current industry dominating heavily doped, directly metalized contacts. A low temperature (≤230 °C), TiOx/LiFx/Al electron heterocontact is presented here, which achieves mΩcm2 scale contact resistivities ρc on lowly doped n‐type substrates. As an extreme demonstration of the potential of this heterocontact, it is trialed in a newly developed, high efficiency n‐type solar cell architecture as a partial rear contact (PRC). Despite only contacting ≈1% of the rear surface area, an efficiency of greater than 23% is achieved, setting a new benchmark for n‐type solar cells featuring undoped PRCs and confirming the unusually low ρc of the TiOx/LiFx/Al contact. Finally, in contrast to previous versions of the n‐type undoped PRC cell, the performance of this cell is maintained after annealing at 350–400 °C, suggesting its compatibility with conventional surface passivation activation and sintering steps.
CZTS quantum dots are employed as hole transporting materials for CsPbBr3 inorganic perovskite solar cells. More effective hole extraction and transfer properties, as well as stability have been demonstrated after introducing CZTS as the hole selective contact. This work reveals the great promise of CZTS as hole acceptors within inorganic perovskite‐based devices.
All‐inorganic CsPbBr3 perovskite solar cells (PSCs) have recently generated tremendous interest in next‐generation cost‐effective and stable photovoltaic devices. However, the commonly used costly and unstable organic hole transporting material (HTM) has so far prevented the further development and large‐scale application of PSCs. In this work, Cu2ZnSnS4 quantum dots (CZTS QDs) are exploited as a novel inorganic HTM for CsPbBr3 PSCs. Due to the well‐matched energy levels with the inorganic perovskite layer, a decent power conversion efficiency of 4.84% is achieved, which is quite comparable to the efficiency of the traditional device based on spiro‐OMeTAD HTM (5.36%). Moreover, the photoluminescence (PL) and impedance spectroscopy further demonstrate the more effective hole extraction and transfer properties of the CZTS QDs interface layer, making it a promising material for fabricating efficient and stable PSCs toward practical applications.
Energy Environ. Sci., 2019, 12,1309-1316 DOI: 10.1039/C9EE00528E, Paper
Ilario Gelmetti, Núria F. Montcada, Ana Pérez-Rodríguez, Esther Barrena, Carmen Ocal, Inés García-Benito, Agustín Molina-Ontoria, Nazario Martín, Anton Vidal-Ferran, Emilio Palomares In this work, we assess the possible reasons for the differences observed in open circuit voltage (VOC) in mixed cation perovskite solar cells when comparing four different hole transport materials (HTMs), namely TAE-1, TAE-3, TAE-4 and spiro-OMeTAD. The content of this RSS Feed (c) The Royal Society of Chemistry
by Tianhao Wu,
Yanbo Wang,
Xing Li,
Yongzhen Wu,
Xiangyue Meng,
Danyu Cui,
Xudong Yang,
Liyuan Han
A novel method for defects passivation in perovskite solar cells via controlling the electron density distribution of D‐π‐A molecule is proposed. As the polarity of the passivated molecule increases, the passivation effect on the under‐coordinated Pb2+ defects will be more obvious, leading to an increase of 80 mV in the open circuit voltage of the devices.
Abstract
Organic–inorganic hybrid perovskite solar cells (PSCs) are a promising photovoltaic technology that has rapidly developed in recent years. Nevertheless, a large number of ionic defects within perovskite absorber can serve as non‐radiative recombination center to limit the performance of PSCs. Here, organic donor‐π‐acceptor (D‐π‐A) molecules with different electron density distributions are employed to efficiently passivate the defects in the perovskite films. The X‐ray photoelectron spectroscopy (XPS) analysis shows that the strong electron donating N,N‐dibutylaminophenyl unit in a molecule causes an increase in the electron density of the passivation site that is a carboxylate group, resulting in better binding with the defects of under‐coordinated Pb2+ cations. Carrier lifetime in the perovskite films measured by the time‐resolved photoluminescence spectrum is also prolonged by an increase in donation ability of the D‐π‐A molecules. As a consequence, these benefits contribute to an increase of 80 mV in the open circuit voltage of the devices, enabling a maximum power conversion efficiency (PCE) of 20.43%, in comparison with PCE of 18.52% for the control device. The authors' findings provide a novel strategy for efficient defect passivation in the perovskite solar cells based on controlling the electronic configuration of passivation molecules.
