Bulk heterojunction perovskite solar cells incorporated with solution-processed TiOx nanoparticles as the electron acceptors

In the past ten years, perovskite solar cells were rapidly developed, but the intrinsic unbalanced charge carrier diffusion lengths within perovskite materials were not fully addressed by either a planar heterojunction or meso-superstructured perovskite solar cells. In this study, we report bulk heterojunction perovskite solar cells, where perovskite materials CH₃NH₃PbI₃ is blended with solution-processed n-type TiO_x nanoparticles as the photoactive layer. Studies indicate that one-step solution-processed CH₃NH₃PbI₃:TiO_x bulk-heterojunction thin film possesses enhanced and balanced charge carrier mobilities, superior film morphology with enlarged crystal sizes, and suppressed trap-induced charge recombination. Thus, bulk heterojunction perovskite solar cells by CH₃NH₃PbI₃ mixed with 5 wt% of TiO_x, which is processed by one-step method rather than typical two-step method, show a short-circuit current density of 20.93 mA/cm², an open-circuit voltage of 0.90 V, a fill factor of 80% and with a corresponding power conversion efficiency of 14.91%, which is more than 30% enhancement as compared with that of perovskite solar cells with a planar heterojunction device structure. Moreover, bulk heterojunction perovskite solar cells possess enhanced device stability. All these results demonstrate that perovskite solar cells with a bulk heterojunction device structure are one of apparent approaches to boost device performance.     

Highly Efficient,Reproducible, Uniform (CH3NH3)PbI3 Layer by Processing Additive Dripping for Solution‐Processed Planar Heterojunction Perovskite Solar Cells

A processing additive dripping (PAD) approach to forming highly efficient (CH₃NH₃)PbI₃ (MAPbI₃) perovskite layers was investigated. A MAPbI₃(CB/DIO) perovskite film fabricated by this approach, which included briefly dripping chlorobenzene incorporating a small amount of diiodooctane (DIO) during casting of a MAPbI₃ perovskite precursor dissolved in dimethylformamide, exhibited superior smooth, uniform morphologies with high crystallinity and large grains and revealed completely homogeneous surface coverage. The surface coverage and morphology of the substrate significantly affected the photovoltaic performance of planar heterojunction (PHJ) perovskite solar cells (PrSCs), resulting in a power conversion efficiency of 11.45 % with high open‐circuit voltage of 0.91 V and the highest fill factor of 80.87 %. Moreover, the PAD approach could effectively provide efficient MAPbI₃(CB/DIO) perovskite layers for highly efficient, reproducible, uniform PHJ PrSC devices without performance loss or variation even over larger active areas.     

Preparation and characterization of planar heterojunction perovskite solar cells based on c-TiO2/CH3NH3PbI3/HTM/Ag structure

Journal of Sol-Gel Science and Technology - In this paper, A modified one-step method was used to prepare the CH3NH3PbI3 (MAPbI3) perovskite film, and the planar heterojunction perovskite solar...     

A repeated interdiffusion method for efficient planar formamidinium perovskite solar cells

A repeated interdiffusion method is described for phase-stable and high-quality(FA,MA)PbI_3 film. The crystallization and growth of the perovskite films can be well controlled by adjusting the reactant concentrations.With this method, dense, smooth perovskite films with large crystals have been obtained. Finally, a PCE of 16.5% as well as a steady-state efficiency of 16.3% is achieved in the planar perovskite solar cell.     

Fabrication and properties of mineralized collagen‐chitosan/hydroxyapatite scaffolds

A hydroxyapatite (HAp)/biopolymer composite scaffold was fabricated by mineralizing a crosslinked collagen/chitosan, which was pre‐mineralized with Ca²⁺ and phosphate salts, in simulated body fluid (SBF) for only 24 hr. A self‐organized structure similar to bone is expected. Microstructures of the crosslinked collagen/chitosan scaffold, the pre‐mineralized collagen–chitosan scaffold (CCS), and the mineralized collagen‐chitosan/HAp scaffolds (MCCHS) were characterized by scanning electron microscopy (SEM), revealing non‐alteration of the porous structure and formation of the HAp particles. X‐ray diffractometer (XRD) confirmed the crystalline structure of the HAp. Thermal gravimetric analysis found that more HAp particles were formed when the CCSs were pre‐mineralized in a higher concentration of Ca²⁺. Water‐uptake ratio of the crosslinked CCS was ～160, decreased to ～120 after incubating in Ca²⁺ solution, and further decreased to ～20 after mineralization. Mechanical strength of the CCS was improved significantly after the in situ mineralization too. The method introduced here may be potentially applied to obtain other biopolymer/HAp composite in a short period. Copyright © 2008 John Wiley & Sons, Ltd.     

TiO_2 nanoparticle-based electron transport layer with improved wettability for efficient planar-heterojunction perovskite solar cell

The electron transport layer(ETL) plays an important role in planar heterojunction perovskite solar cell(PSCs),by affecting the light-harvesting, electron injection and transportation processes, and especially the crystallization of perovskite absorber. In this work, we utilized a commercial TKD-TiO_2 nanoparticle with a small diameter of 6 nm for the first time to prepare a compact ETL by spin coating. The packing of small-size particles endowed TKD-TiO_2 ETL an appropriate surface-wettability, which is beneficial to the crystallization of perovskite deposited via solution-processed method. The uniform and high-transmittance TKD-TiO_2 films were successfully incorporated into PSCs as ETLs. Further careful optimization of ETL thickness gave birth to a highest power conversion efficiency of 11.0%, which was much higher than that of PSC using an ETL with the same thickness made by spray pyrolysis. This TKD-TiO_2 provided a universal solar material suitable for the further large-scale production of PSCs. The excellent morphology and the convenient preparation method of TKD-TiO_2 film gave it an extensive application in photovoltaic devices.     

Anti-solvent assisted treatment for improved morphology and efficiency of lead acetate derived perovskite solar cells

An efficient solution-processable route employing Pb(Ac)₂ as lead source and anti-solvent treatment to achieve fully covered and homogenous perovskite films is reported.     

Semi‐Locked Tetrathienylethene as a Building Block for Hole‐Transporting Materials: Toward Efficient and Stable Perovskite Solar Cells

The construction of state‐of‐the‐art hole‐transporting materials (HTMs) is challenging regarding the appropriate molecular configuration for simultaneously achieving high morphology uniformity and charge mobility, especially because of the lack of appropriate building blocks. Herein a semi‐locked tetrathienylethene (TTE) serves as a promising building block for HTMs by fine‐tuning molecular planarity. Upon incorporation of four triphenylamine groups, the resulting TTE represents the first hybrid orthogonal and planar conformation, thus leading to the desirable electronic and morphological properties in perovskite solar cells (PSCs). Owing to its high hole mobility, deep lying HOMO level, and excellent thin film quality, the dopant‐free TTE‐based PSCs exhibit a very promising efficiency of over 20 % with long‐term stability, achieving to date the best performances among dopant‐free HTM‐based planar n‐i‐p structured PSCs.     

两亲性季铵盐对钙钛矿太阳能电池效率和稳定性的影响

将廉价易得的两亲性季铵盐十六烷基三甲基溴化铵（CTMAB）加入到钙钛矿前驱体溶液中，通过调节添加量研究了CTMAB对钙钛矿太阳能电池效率和稳定性的影响.结果表明，加入CTMAB后制备的钙钛矿薄膜更加致密均匀，表面缺陷更少，钙钛矿晶体结晶性得到显著提高，从而提高了电池的光电转换效率及电池稳定性；含有CTMAB的钙钛矿太阳能电池的光电转换效率（PCE）为18.03%，明显高于未添加CTMAB的电池效率（17.05%）；含有CTMAB的电池稳定性有较大的提高，在一定湿度环境中保存40 d后效率仍达初始效率的95%，而未添加CTMAB的器件效率只有初始效率的70%.     

高效钙钛矿太阳能电池吸光层的设计与优化

本文设计了多元混合钙钛矿吸光层涂布液配方,并采用两步法组装了钙钛矿电池器件。由于两步法制备钙钛矿吸光层存在配方和工艺相对复杂的问题,导致电池器件性能难以提升,因此,本文采用正交实验的方法,筛选出影响电池器件性能的关键因素。针对关键因素设计了系列实验,通过观察钙钛矿层薄膜形貌,测试钙钛矿太阳能电池器件的光电性能,并采用多种表征手段研究了钙钛矿层薄膜性质,确定了关键因素的添加量,最后优选出钙钛矿电池吸光层的最佳配方,得到高质量的钙钛矿薄膜,电池的光电转换效率达到21.1%。     

Supersaturation controlled growth of MAFAPbI<Subscript>3</Subscript> perovskite film for high efficiency solar cells

Controlling the nucleation and growth of organic-inorganic hybrids perovskite is of key importance to improve the morphology and crystallinity of perovskite films. However, the growth mechanism of perovskite films based on classical crystallization theory is not fully understood. Here, we develop a supersaturation controlled strategy (SCS) to balance the nucleation and crystal growth speeds. By this strategy, we are able to find an ideal supersaturation region to realize a balance of nucleation and crystal growth, which yields highly crystallized perovskite films with micrometer-scale grains. Besides, we provide a thoughtful analysis of nucleation and growth based on the fabrication of the perovskite films. As a result, the highest photovoltaic power conversion efficiencies (PCE) of 19.70% and 20.31% are obtained for the planar and the meso-superstructured devices, respectively. This strategy sheds some light for understanding the film growth mechanism of high quality perovskite film, and it provides a facile strategy to fabricate high efficiency perovskite solar cells.     

Supersaturation controlled growth of MAFAPbI_3 perovskite film for high efficiency solar cells

Controlling the nucleation and growth of organic-inorganic hybrids perovskite is of key importance to improve the morphology and crystallinity of perovskite films. However, the growth mechanism of perovskite films based on classical crystallization theory is not fully understood. Here, we develop a supersaturation controlled strategy(SCS) to balance the nucleation and crystal growth speeds. By this strategy, we are able to find an ideal supersaturation region to realize a balance of nucleation and crystal growth, which yields highly crystallized perovskite films with micrometer-scale grains. Besides, we provide a thoughtful analysis of nucleation and growth based on the fabrication of the perovskite films. As a result, the highest photovoltaic power conversion efficiencies(PCE) of 19.70% and 20.31% are obtained for the planar and the meso-superstructured devices, respectively. This strategy sheds some light for understanding the film growth mechanism of high quality perovskite film, and it provides a facile strategy to fabricate high efficiency perovskite solar cells.     

Perylene Bisimides as efficient electron transport layers in planar heterojunction perovskite solar cells

Two perylene bisimides based non-fullerene small molecules, H-DIPBI and B-DIPBI, are applied into inverted planar heterojunction perovskite solar cells. The power conversion efficiency up to 11.6% has been achieved for device with B-DIPBI, indicating that non-fullerene acceptor can function as the electron transport layer to replace PCBM in perovskite solar cells.     

A Fast Deposition‐Crystallization Procedure for Highly Efficient Lead Iodide Perovskite Thin‐Film Solar Cells

Thin‐film photovoltaics based on alkylammonium lead iodide perovskite light absorbers have recently emerged as a promising low‐cost solar energy harvesting technology. To date, the perovskite layer in these efficient solar cells has generally been fabricated by either vapor deposition or a two‐step sequential deposition process. We report that flat, uniform thin films of this material can be deposited by a one‐step, solvent‐induced, fast crystallization method involving spin‐coating of a DMF solution of CH₃NH₃PbI₃ followed immediately by exposure to chlorobenzene to induce crystallization. Analysis of the devices and films revealed that the perovskite films consist of large crystalline grains with sizes up to microns. Planar heterojunction solar cells constructed with these solution‐processed thin films yielded an average power conversion efficiency of 13.9±0.7 % and a steady state efficiency of 13 % under standard AM 1.5 conditions.     

Synthesis of hybrid organic-inorganic perovskite platelets by vacuum impregnation

In perovskite solar cells and optoelectronics, perovskite film morphology controls the performance of the device. Various methods have been developed to control the morphology and coverage of the perovskite films. In this article platelet type perovskite morphlogy was synthesized using low temperature vacuum impregnation of the perovskite solution CH₃NH₃PbI₃ resulting in complete coverage on TiO₂ film. Vacuum impregnation synthesis of perovskites has the advantage of low cost and low temperature which faciliates application in flexible electronics and solar cells.     

Antioxidant Grain Passivation for Air‐Stable Tin‐Based Perovskite Solar Cells

Tin‐based perovskites with excellent optoelectronic properties and suitable band gaps are promising candidates for the preparation of efficient lead‐free perovskite solar cells (PSCs). However, it is challenging to prepare highly stable and efficient tin‐based PSCs because Sn²⁺ in perovskites can be easily oxidized to Sn⁴⁺ upon air exposure. Here we report the fabrication of air‐stable FASnI₃ solar cells by introducing hydroxybenzene sulfonic acid or its salt as an antioxidant additive into the perovskite precursor solution along with excess SnCl₂. The interaction between the sulfonate group and the Sn²⁺ ion enables the in situ encapsulation of the perovskite grains with a SnCl₂–additive complex layer, which results in greatly enhanced oxidation stability of the perovskite film. The corresponding PSCs are able to maintain 80 % of the efficiency over 500 h upon air exposure without encapsulation, which is over ten times longer than the best result reported previously. Our results suggest a possible strategy for the future design of efficient and stable tin‐based PSCs.     

离子液体对钙钛矿太阳能电池性能的影响

利用1-乙基-3-甲基咪唑溴盐(EMIMBr)、1-己基-3-甲基咪唑溴盐(HMIMBr)、双三氟甲烷磺酰亚胺锂(LiTFSI)以及1-乙基-3-甲基咪唑氯盐(EMICl)和双氟磺酰亚胺钾(KFSI)制备了1-乙基-3-甲基咪唑双三氟甲磺酰亚胺盐(EMITFSI)、1-己基-3-甲基咪唑双三氟甲磺酰亚胺盐(HMITFSI)和1-乙基-3-甲基咪唑鎓二(氟甲磺酰基)亚胺盐(EMIFSI)3种离子液体。 用氯苯稀释的离子液体对钙钛矿活性层进行浸泡处理,探究了离子液体对钙钛矿形貌以及钙钛矿太阳能电池性能的影响。 结果表明,HMITFSI处理后太阳能电池的填充因子从0.71提高到了0.74,光电转换效率也有了一定提高,钙钛矿薄膜的表面形貌得到了改善,而EMITFSI和EMIFSI的处理反而降低了钙钛矿太阳能电池的性能,证实离子液体可以影响钙钛矿的结晶形貌。     

Lead‐Free Solar Cells based on Tin Halide Perovskite Films with High Coverage and Improved Aggregation

Two simple methods to improve tin halide perovskite film structure are introduced, aimed at increasing the power conversion efficiency of lead free perovskite solar cells. First, a hot antisolvent treatment (HAT) was found to increase the film coverage and prevent electrical shunting in the photovoltaic device. Second, it was discovered that annealing under a low partial pressure of dimethyl sulfoxide vapor increased the average crystallite size. The topographical and electrical qualities of the perovskite films are substantively improved as a result of the combined treatments, facilitating the fabrication of tin‐based perovskite solar cell devices with power conversion efficiencies of over 7 %.     

Controlled Orientation in a Bio‐Inspired Assembly of Ag/AgCl/ZnO Nanostructures Enables Enhancement in Visible‐Light‐Induced Photocatalytic Performance

In a bio‐inspired approach, polyamine‐mediated mineralization of ZnO was explored to develop an environmentally benign methodology for synthesizing Ag/AgCl/ZnO nanostructures. The assembling properties displayed by the polyamines to create composite structures was utilized to have the nanocomponents effectively interact with each other in a way that is desirable for the application envisaged. The polyamines, which act as a mineralizing agent for ZnO nanoparticles, also facilitate the formation of Ag/AgCl within ZnO under ambient conditions. Thus synthesized Ag/AgCl/ZnO nanostructures represent a multi‐heterojunction system in which the nanocomponents lead in a synergistic way to enhancement in the photocatalytic activity under visible‐light irradiation.     

In-situ fabrication of dual porous titanium dioxide films as anode for carbon cathode based perovskite solar cell

We develop a dual porous(DP) TiO_2 film for the electron transporting layer(ETL) in carbon cathode based perovskite solar cells(C-PSCs). The DP TiO_2 film was synthesized via a facile PS-templated method with the thickness being controlled by the spin-coating speed. It was found that there is an optimum DP TiO_2 film thickness for achieving an effective ETL, a suitable perovskite/TiO_2 interface, an efficient light harvester and thus a high performance C-PSC. In particular, such a DP TiO_2 film can act as a scaffold for complete-filling of the pores with perovskite and for forming high-quality perovskite crystals that are seamlessly interfaced with Ti_O2 to enhance interfacial charge injection. Leveraging the unique advantages of DPTiO2 ETL, together with a dense-packed and pinhole-free TiO_2 compact layer, PCE of the C-PSCs has reached 9.81% with good stability.