Chen Weijie

Publication date: 19 October 2022

Source: Joule, Volume 6, Issue 10

Author(s): Seongwon Yoon, Sungmin Park, So Hyun Park, Sanghee Nah, Seungjin Lee, Jin-Woo Lee, Hyungju Ahn, Hyeonggeun Yu, Eul-Yong Shin, Bumjoon J. Kim, Byoung Koun Min, Jun Hong Noh, Hae Jung Son

Publication date: 21 September 2022

Source: Joule, Volume 6, Issue 9

Author(s): Loreta A. Muscarella, Bruno Ehrler

Publication date: 21 September 2022

Source: Joule, Volume 6, Issue 9

Author(s): Lingfeng Chao, Yingdong Xia, Xiaozheng Duan, Yue Wang, Chenxin Ran, Tingting Niu, Lei Gu, Deli Li, Jianfei Hu, Xingyu Gao, Jing Zhang, Yonghua Chen

Here, the authors report a highly efficient integrated ideal-bandgap perovskite/bulk-heterojunction solar cell (IPBSC) with an inverted architecture, featuring a near infrared (NIR) polymer DTBTI based bulk-heterojunction (BHJ) layer atop guanidinium bromide (GABr)-modified FA_0.7MA_0.3Pb_0.7Sn_0.3I₃ perovskite film as the photoactive layer. As a result, the IPBSCs achieve a lab power conversion efficiency (PCE) of 24.27% along with certificated value at 23.4%, currently the recorded efficiency for both IPBSCs and Pb-Sn alloyed PSC.

Abstract

Here, the authors report a highly efficient integrated ideal-bandgap perovskite/bulk-heterojunction solar cell (IPBSC) with an inverted architecture, featuring a near infrared (NIR) polymer DTBTI-based bulk-heterojunction (BHJ) layer atop guanidinium bromide (GABr)-modified FA_0.7MA_0.3Pb_0.7Sn_0.3I₃ perovskite film as the photoactive layer. The IPBSC shows cascade-like energy level alignment between the charge-extractionlayer/perovskite/BHJ and efficient passivation effect of BHJ on perovskite. Thanks to the well-matched energy level alignment and high-quality ideal bandgap-based perovskite film, an efficient charge transfer occurs between the charge-extraction-layer/perovskite/BHJ. Moreover, the NIR polymer DTBTI on the perovskite film leads to an improved NIR light response for the IPBSC. In addition, the O, S and N atoms in the DTBTI polymer yield a strong interaction with perovskite, which is conducive to reducing the defects of the perovskite and suppressing charge recombination. As a result, the solar cell achieves a power conversion efficiency (PCE) of 24.27% (certificated value at 23.4% with 0.283-volt voltage loss), currently the recorded efficiency for both IPBSCs and Pb-Sn alloyed PSCs, and which is over the highest efficiency of perovskite–organic tandem solar cell. Moreover, the thermal, humidity and long-term operational stabilities of the IPBSCs are also significantly improved compared with the control PSCs.

An ultrathin hybrid hole transporting layer employing NiO_x/[2-(9H-carbazol-9-yl) ethyl]phosphonic acid enables complete and uniform coverage on fully textured indium tin oxide (ITO)/silicon surface with pyramid structures of 2–5 µm sizes. As a result of the depleted shunt pathways between ITO and perovskite top cell, a certified record efficiency—28.84%—is achieved on perovskite/silicon tandem solar cells with fully textured, production-line compatible bottom silicon wafers.

Abstract

Perovskite/silicon tandem solar cells are promising avenues for achieving high-performance photovoltaics with low costs. However, the highest certified efficiency of perovskite/silicon tandem devices based on economically matured silicon heterojunction technology (SHJ) with fully textured wafer is only 25.2% due to incompatibility between the limitation of fabrication technology which is not compatible with the production-line silicon wafer. Here, a molecular-level nanotechnology is developed by designing NiO_x/2PACz ([2-(9H-carbazol-9-yl) ethyl]phosphonic acid) as an ultrathin hybrid hole transport layer (HTL) above indium tin oxide (ITO) recombination junction, to serve as a vital pivot for achieving a conformal deposition of high-quality perovskite layer on top. The NiO_x interlayer facilitates a uniform self-assembly of 2PACz molecules onto the fully textured surface, thus avoiding direct contact between ITO and perovskite top-cell for a minimal shunt loss. As a result of such interfacial engineering, the fully textured perovskite/silicon tandem cells obtain a certified efficiency of 28.84% on a 1.2-cm² masked area, which is the highest performance to date based on the fully textured, production-line compatible SHJ. This work advances commercially promising photovoltaics with high performance and low costs by adopting a meticulously designed HTL/perovskite interface.

Chemical modification of tin perovskites by biocompatible multidentate chelators realized “inside-out” healing of structural imperfections and manipulation of carrier dynamics, delivering an efficiency up to 13.70 % with enhanced long-term stability over 1200 h.

Abstract

Tin-based perovskite solar cells (Sn-PSCs) have emerged as promising environmentally viable photovoltaic technologies, but still suffer from severe non-radiative recombination loss due to the presence of abundant deep-level defects in the perovskite film and under-optimized carrier dynamics throughout the device. Herein, we healed the structural imperfections of Sn perovskites in an “inside-out” manner by incorporating a new class of biocompatible chelating agent with multidentate claws, namely, 2-Guanidinoacetic acid (GAA), which passivated a variety of deep-level Sn-related and I-related defects, cooperatively reinforced the passivation efficacy, released the lattice strain, improved the structural toughness, and promoted the carrier transport of Sn perovskites. Encouragingly, an efficiency of 13.7 % with a small voltage deficit of ≈0.47 V has been achieved for the GAA-modified Sn-PSCs. GAA modification also extended the lifespan of Sn-PSCs over 1200 hours.

Nature Communications, Published online: 19 August 2022; doi:10.1038/s41467-022-32482-y

A polymer design strategy was proposed by managing the donor and acceptor building blocks with longitudinal extended conjugation for dopant-free hole transport materials (HTMs). The optimized device based on the polymer HTM constructed by longitudinal extended BDT-T and BDD units shows a champion power conversion efficiency of 24.04 % and greatly improved operational stability.

Abstract

The dominant hole transport material (HTM) in state-of-the-art perovskite solar cells (PSCs) is Spiro-OMeTAD, which needs to be doped using hydrophilic dopants to improve its hole mobility and conductivity, resulting in inferior device stability. Here, we propose an effective molecular design strategy to construct dopant-free polymer HTMs by selecting four structurally related polymers and investigating their structure–property relationship. It is found that the donor and acceptor units with longitudinal conjugate extension, such as BDT-T and BDD, could not only enhance the planarity of the conjugated polymer backbone and tune the energy levels but also promote the face-on orientation, resulting in superior charge extraction and transport. The optimized device utilizing dopant-free polymer HTM shows a high open-circuit voltage of 1.19 V and a champion efficiency of 24.04 % with greatly improved operational stability, making it among the best performance PSCs based on dopant-free HTMs.

Methylammonium chloride is added in chlorobenzene and isopropanol co-anti-solvent to post-treat the Sn–Pb mixed perovskite (PVSK), which induces more Sn-rich PVSK grains formed on the bottom, and more Pb-rich crystal particles on the top surface. The PVSK surface is eventually terminated with a Pb-rich shell, leading to the PVSK more humidity-stable and more suitable for photoelectric conversion.

Low bandgap tin–lead halide perovskite (PVSK) presents promising opportunities for high-performance solar cells. However, the randomly crystallized Sn–Pb PVSK with a tin-rich surface is easily oxidized, leading to high-level p-type doping, which hinders the performance enhancement of the solar cell devices. Herein, an efficient anti-solvent passivation strategy to regulate defect, crystallization, and energy conversion performance based on anti-solvents composed of chlorobenzene, isopropanol, and methylammonium chloride (MACl) is proposed. It is shown that the Sn–Pb PVSK film gets more moderate and order, with less PbI₂ and more α-phase PVSK formed. Furthermore, it is revealed that the surface of the as-processed film is Pb-rich, demonstrating a decrease in the surface p-type concentration, which is more suitable for the photoelectric conversion enhancement of the inverting device. Finally, the MACl-assisted post-treated Sn–Pb PVSK invert solar cells exhibit a high current density of 26.49 mA cm⁻² with a open-circuit voltage of 0.70 V and a power conversion efficiency of 16.05%. The modified anti-solvent process fuses the advantage of additive and anti-solvent engineering for growing highly crystallized hybrid tin-lead halide PVSK for photovoltaic devices.

The proportion of the facet (001) of PbI₂ crystals increases as the synthesis temperature increases and fabricates better formamidinium-based perovskite films. The perovskite solar cells based on the PbI₂ synthesized at 120 °C exhibit the best power conversion efficiency (PCE) of 17.96% and the module with an active area of 3.68 cm² shows a PCE of 16.08%.

Perovskite solar cells (PSCs) have been the promising stars in the solar cell industry for dramatically improving the power conversion efficiency (PCE) in the past decade and reaching a record over 25%. However, there are still many issues to be solved on an industrial scale. One of these challenges is the material stability of precursors, which may significantly affect the performance of PSCs. Herein, a facile method is provided to produce controllable lead iodide as the raw material for formamidinium-based PSCs whose performance is highly correlated to the crystallographic-preferred orientation of PbI₂. The PSCs based on the PbI₂ synthesized at 120 °C exhibit the best PCE of 17.96% among these solar cells. Furthermore, the perovskite solar module with an active area of 3.68 cm² and a PCE of 16.08% is successfully demonstrated, showing the potential of scaling up in the future.

The undesirable δ-FAPbI₃ is introduced onto the surface of the perovskite film, which could form a type-I band structure with perovskite and protect the perovskite layer from moisture invasion, resulting in less nonradiative charge recombination and higher film stability. The resultant δ-FAPbI₃/perovskite-based perovskite solar cells achieve an efficiency of 23.10% with excellent stablility under various aging conditions.

Abstract

Yellow-phase formamidinium lead iodide (δ-FAPbI₃) as a degradation product of black perovskite phase is usually unwelcome in perovskite solar cells (PSCs). However, it also shows high potential in passivating defects and protecting perovskite films from moisture intrusion due to its water-stable nature. Herein, the utilization of δ-FAPbI₃ to construct a yellow/black heterophase bilayer is reported, in which the perovskite layer is shielded by in situ formed δ-FAPbI₃ species on the surface, for PSCs with enhanced efficiency and stability. It is found that the δ-FAPbI₃ layer with a broader bandgap than the black-phase perovskite can efficiently suppress the charge recombination at the interface, offering a high PSC efficiency of 23.10%. More importantly, the δ-FAPbI₃-modified devices exhibit preferable stability against various external stresses to that of the control ones. Compared to those using the disliked δ-FAPbI₃ in the literature, the strategy, which maximizes its merits in reducing the interfacial charge recombination and stabilizing the perovskite structure, is more simple yet effective to realize highly efficient and stable PSCs.

A facile ion compensation strategy is collaboratively proposed by using an ammonium salt to pre-treat the buried hole-transporting material (CuScO₂)/perovskite interfaces for an inverted device, resulting in impressive device efficiency (MA-free: 22.42%) with improved operational stability. The present strategy can be extended to triple-cation mixed perovskite solar cells with a champion PCE of 23.11%.

Abstract

The development of inorganic hole-transporting materials (HTMs) is one of the most reliable ways to improve the stability of perovskite solar cells (PSCs). However, the un-optimal buried interfacial contacts and the defects located at the inorganic HTMs/perovskite interface restricted the device's performance. Herein, a phase-pure CuScO₂ has been synthesized and further employed as mesoporous HTM in inverted PSCs. Surprisingly, a facile pretreatment of the hole-transport layer by a formamidine salt compensates the I⁻ vacancy of the buried perovskite film, thus regulating the interfacial band energy alignment between the HTM and perovskite. This ion compensation strategy can not only in situ repair the ion loss and improve the built-in electric field, but also decrease the charge injection barrier and suppress the non-radiative interfacial recombination. Benefiting from these merits, the resulting methylammonium-free (MA), Cs/FA-based PSCs displays a power conversion efficiency (PCE) of 22.42% along with excellent thermal and light stability. Moreover, the pre-buried treatment strategy can be extended to MA-containing CsFAMA triple-cation perovskite film, and a champion inverted device delivers a PCE of 23.11%. This study offers a new avenue to the rational design of HTMs for highly efficient and stable PSCs.

Donor/acceptor interfacial properties strongly influence the performance of organic photovoltaics via processes such as charge transfer, delocalization, and recombination that can set the fundamental efficiency limit of such devices. The screening of this interface can provide the tools (interfacial modification) to optimize the trade-off in device figure of merit.

Abstract

Organic photovoltaics (OPVs) have demonstrated increasing potential for use in large-area, flexible, and light-weight applications. To date, the rapid development of nonfullerene acceptors (NFAs) and their conjugated polymeric donors have increased the efficiency of OPV by over 19%. Nevertheless, OPV is still suffering from high energy loss, which primarily derives from the donor (D)/acceptor (A) interfacial charge recombination. In particular, the voltage loss occurring at the D/A interface accounts for the current bottleneck, hampering further enhancement of the OPV efficiency. In this review, the recent discovery of D/A interfacial photophysics in NFA-based OPVs, including the comparison with its fullerene-based counterpart, is covered. Additionally, the factors governing interfacial energy loss, such as interfacial energetics and local morphologies, which causes the trade-off relationship between photovoltage and photocurrent in OPV are highlighted. Accordingly, the control of D/A interfacial properties to create an “ideal” interface for charge generation in OPVs is reviewed; and emphasized that the D/A interfacial modifications can serve as a powerful tool to manage the challenges in OPVs path toward future practical applications.

Perovskite photovoltaics are ideal to efficiently recycle stray light that normally is wasted in certain illumination devices. A proof of that is demonstrated here, where the optical and photovoltaic characterization of the elements that compose an innovative light recycling design to emit polarized diffused light are presented.

Abstract

Perovskite based photovoltaic (PV) cells are unique in combining low open-circuit voltage losses with a broad bandgap tunability. This makes them an ideal PV cell to recycle photons back into electrical power in a variety of illumination systems or light emitting devices. Here, advantage of these features is taken and wide bandgap (WBG) perovskite PV cells are incorporated in devices suitable for display illumination and demonstrate a high yield in stray light recycling back into electricity with up to a 37.5% power conversion efficiency. The specific device considered is a modified half-cylinder photonic plate designed to emit diffused broadband polarized light using a nonabsorbing reflective polarizer based on a random dielectric layer distribution. It is experimentally demonstrated that light recycling using appropriately tuned WBG perovskite PV cells becomes very efficient when implemented in systems where the light is emitted from narrowband sources, even if the emission spans a broad wavelength range.

This work reports a p-type additive, fluorinated graphene, for Spiro-OMeTAD hole transporting layers, which improves hydrophobicity and suppresses carrier recombination at the Spiro-OMeTAD/perovskite interface. A perovskite solar cell with fluorinated graphene doped Spiro-OMeTAD achieves a power conversion efficiency of over 23% and long-term humidity stability of 4600 h.

Abstract

Spiro-OMeTAD is one of the most used hole transport layers (HTLs) in high efficiency n-i-p perovskite solar cells (PSCs). However, due to the unsatisfactory conductivity of pristine Spiro-OMeTAD, additives such as tert-butylpyridine (tBP) and lithium bis (trifluoromethylsulfonyl)-imide (LiTFSI) are required to improve its hole transportation. The hygroscopic nature of these additives inevitably deteriorates the device's stability. Here, it is shown that by adding fluorinated graphene (FG) into the Li-TFSI and tBP doped Spiro-OMeTAD, both efficiency and stability of the PSCs are significantly enhanced. Using the FG incorporated Spiro-OMeTAD HTL, the power conversion efficiency (PCE) of the PSC reaches 21.92%, which is 11.8% higher than the original device. The FG not only improves the hole mobility of Spiro-OMeTAD but also effectively reduces the amount of lithium ions in the perovskite layer and improves the hydrophobicity of the HTL. The FG incorporating cell shows better stability, maintaining 90% of initial efficiency over a 2400 h test in ambient conditions with 25% humidity. Finally, it is further demonstrated that the valence band of FG incorporated Spiro-OMeTAD HTL has a positive effect on PSCs with a 2D interfacial layer, achieving an impressive PCE of 23.14% and a Voc of 1.226 V.

A deep-learning approach is developed to automatically and accurately assign the structure type from the X-ray diffraction patterns of new hybrid lead halides. An accuracy of 92% is obtained and the new insights provided by the model allow the ability of scientists to discriminate manually between different structure types of new materials to be augmented.

Abstract

Determining the crystal structure is a critical step in the discovery of new functional materials. This process is time consuming and requires extensive human expertise in crystallography. Here, a machine-learning-based approach is developed, which allows it to be determined automatically if an unknown material is of perovskite type from powder X-ray diffraction. After training a deep-learning model on a dataset of known compounds, the structure types of new unknown compounds can be predicted using their experimental powder X-ray diffraction patterns. This strategy is used to distinguish perovskite-type materials in a series of new hybrid lead halides. After validation, this approach is shown to accurately identify perovskites (accuracy of 92% with convolutional neural network). From the identification of the key features of the patterns used to discriminate perovskites versus nonperovskites, crystallographers can learn how to quickly identify low-dimensional perovskites from X-ray diffraction patterns.