Mahui

Perovskite solar cells (PVSCs) with discrete SnO₂ nanoparticle modification layers are constructed via spin coating the SnO₂ dispersions on poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The discrete SnO₂ nanoparticle film let holes pass and block electrons to diffuse toward PEDOT:PSS, which enhances the extraction efficiency, leading to an increase in a power conversion efficiency of p‐i‐n‐type PVSCs.

Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most widely used hole transport materials for perovskite solar cells (PVSCs) with a p‐i‐n structure. However, the solar cells based on PEDOT:PSS show a low photoconversion efficiency due to the poor crystallinity of a perovskite film on it. Besides, the acidity of PEDOT:PSS performance critically influences the long‐term stability of PVSCs. Herein, a layer of the discrete SnO₂ nanoparticle film is deposited on the surface of PEDOT:PSS to modify the surface of the PEDOT:PSS film. This discrete SnO₂ nanoparticle film acts as the buffer layer between the PEDOT:PSS and MAPbI₃, which not only improves the crystallization of the quality of the perovskite film, but also provides a selective‐carrier pathway to enhance the extraction of holes and to block the diffusion of electrons. The SnO₂ modified devices show a power conversion efficiency of 18.04%, with a great improvement compared with the 12.24% efficiency of PEDOT:PSS only devices. This work demonstrates that it is possible to enhance the performance of PVSCs via n‐type nanoparticle modification of hole transport layer and provides a new guidance for PVSCs interface modification engineering.

A bifunctional dye molecule, 5,15‐bis(2,6‐dioctoxyphenyl)‐10‐(bis(4‐hexylphenyl)‐amino‐20‐4‐carboxyphenylethynyl)porphyrinato]zinc(II) (YD₂‐o‐C8), is introduced into CsPbI₂Br PSCs. It not only broadens the light absorption range of the perovskite but also reduces the energy loss (E _loss) by interface passivation. As a result, the efficiency markedly enhances from 7.02% to 10.13%, featuring a short‐circuit current (J _SC) of 12.05 mA cm⁻² and a record‐high open‐circuit voltage (V _OC) of 1.37 V.

Inorganic lead halide perovskites are attracting increasing attention due to their much better thermal stability than the organic–inorganic hybrid perovskite materials. Thus, the low power conversion efficiency (PCE) is a key issue for the inorganic lead halide perovskite solar cells (PSCs). This is mainly due to their wider bandgap and larger energy loss (E _loss) in the devices. Herein, for solving this issue, a dye molecule‐assisted engineering using the dye of 5,15‐bis(2,6‐dioctoxyphenyl)‐10‐(bis(4‐hexylphenyl)‐amino‐20‐4‐carboxyphenylethynyl)porphyrinato]zinc(II) (YD₂‐o‐C8) is demonstrated. Results indicate that this molecule has a bifunctional effect, not only as a co‐sensitization layer for CsPbIBr₂ with broader absorption spectrum but also reduces the E _loss by interface passivation. Specifically, the light absorption range of the photoactive layer is broadened from 600 to nearly 680 nm. At the same time, the interfacial charge recombination is highly reduced. After optimizing, the champion PCE is enhanced from 7.02% to 10.13%, and record‐high open‐circuit voltage (V _OC) of 1.37 V and short‐circuit currents (J _SC) of 12.05 mA cm⁻² are achieved. This study opens a simple and efficient way to improve the efficiency of inorganic PSCs.

For developing low‐cost and high‐efficiency planar perovskite solar cells (PSCs), a straightforward low‐temperature chemical bath deposition process is developed to prepare a Co‐doped TiO₂ (Co‐TiO₂) electron transport layer (ETL); the optoelectrical properties of the TiO₂ ETL are significantly improved by Co‐doping. Finally, the efficiency of the PSCs is increased from 17.40% for TiO₂ to 19.10% for the Co‐TiO₂ ETL.

Planar hybrid perovskite solar cells (PSCs) attract great attention due to their obvious advantages of low‐temperature processing with a high power conversion efficiency (PCE) up to 23.32%. Here, Co‐doped TiO₂ (Co‐TiO₂) deposited by a straightforward low‐temperature chemical bath deposition (CBD) method is explored. Using Co‐TiO₂ as an electron transport layer (ETL) for the planar PSCs, the effects of doping on TiO₂ morphology, electronic properties, and solar cell performance are investigated. The PCE increases to 19.10% when the Co doping concentration is optimized at 5 mol%, an increase of 17.40% compared with that using the pristine TiO₂. Meanwhile, the notorious J–V hysteresis is suppressed to a greater extent. Considering that the low‐temperature CBD is comparable with continuous roll‐to‐roll processing, it makes the process and the Co‐TiO₂ ETL potential candidates for low‐cost commercialization.

The recent progress in double‐metallic lead‐free perovskite materials and devices is comprehensively reviewed. In particular, theory calculation, electronic structure, and fundamental properties of double perovskites are deliberated. The achievements and challenges in their application including solar cells, photon detectors, and laser devices, are summarized. In addition, the viewpoints for future research of this class of perovskites are also provided.

Lead halide perovskite (ABX₃) has attracted considerable attention due to its applicability as absorber layers in highly efficient photovoltaic cells. With regard to the lead toxicity, double‐metallic lead‐free perovskite, A₂B^IB^IIIX₆, in which the neighboring B⁺ and B³⁺ sites in the crystal microstructure are alternately occupied by monovalent‐metal and trivalent‐metal cations, is regarded to be a promising alternative to the widely used lead‐based perovskites. This review aims to summarize the recent advances in the new class of A₂B^IB^IIIX₆ double‐metallic lead‐free perovskites. In particular, the electronic structure, synthesis, property, and their applications in devices, for example, photovoltaics, photodetectors, and light emitting diodes, is carefully classified and presented. Notably, the theoretical calculations point out that there is much room toward potential applications for this new class of perovskite materials. The present review provides a holonomic conclusion and opens new perspectives toward realizing higher performance of A₂B^IB^IIIX₆‐based devices.

Solution‐processable Ga₂O₃ nanocrystals are developed as a novel electron‐transporting layer for high‐performance perovskite solar cells. The smooth film of Ga₂O₃ nanocrystals offers a better interface with perovskite and improves charge transport efficiency. The Ga₂O₃‐based device shows negligible hysteresis unlike the TiO₂‐based analogue.

The electron‐transporting layer (ETL) plays a very important role in perovskite solar cells (PSCs). The traditional TiO₂ ETL exhibits drawbacks such as complex preparation process and low stability. Devices incorporating TiO₂ as the ETL also show large hysteresis that limits their performance. Herein, Ga₂O₃ nanocrystals (NCs), prepared by a solution process, are applied as an ETL in n‐i‐p planar structured PSCs. The Ga₂O₃‐based devices exhibit negligible hysteresis and achieve higher performance than the TiO₂‐based devices. Due to better energy level matching and smoother surface morphology, films of Ga₂O₃ NCs make good interfacial contact with the perovskite top layer, improving the charge transport efficiency. The perovskite layer also exhibits high crystallinity. Unlike TiO₂, which is commonly prepared by high‐temperature sintering or solution hydrolysis, films of Ga₂O₃ NCs can be prepared by solution spin‐coating at a low temperature. This greatly reduces the complexity of fabrication and improves device performance.

Perovskite solar cells are modified by dropping alkylammonium solutions over CH₃NH₃PbI₃ films and lead to an increase in the stability after exposure to humidity. In the presence of the alkylammonium chains, the bulk perovskite is converted to a 2D/3D structure that helps the device to retain its performance for longer.

Hybrid organic and inorganic perovskite solar cells lack long‐term stability, and this negatively impacts the widespread application of this emerging and promising photovoltaic technology. Herein, aiming to increase the stability of perovskite films based on CH₃NH₃PbI₃ and to deeply understand the formation of 2D structures, solutions of alkylammonium chlorides containing 8, 10, and 12 carbons are introduced during the spin‐coating on the surface of 3D perovskite films leading to the in situ formation of 2D structures. It is possible to identify the chemical formulae of some 2D structures formed by X‐ray diffraction and UV–vis analysis of the modified films. Interestingly, the increase in the stability of the CH₃NH₃PbI₃ films due to the formation of a 2D + 3D perovskite network is only possible in planar TiO₂ substrates. The increase in stability of the CH₃NH₃PbI₃ films follows the surfactant molecule order: octylammonium (8C) > decylammonium (1 °C) > dodecylammonium (12C) chlorides > standard. An increase of 17.6% in the lifetime of the devices assembled with octylammonium‐modified perovskite film is observed compared with that of the standard device, which is directly linked to the improvement of the charge carrier lifetimes obtained from time‐correlated single photon counting measurements.

Surface‐modified NiO _x nanoparticles (NPs) as hole transport materials in n‐i‐p‐structured perovskite solar cells are studied. The modified NiO _x NPs disperse well in chlorobenzene, and their film forms smooth and pinhole‐free layers, which show good electrical conductivity and improved extraction properties. The power conversion efficiency is improved from 5.5% to 13.1%.

Modified NiO _x nanoparticles (NPs) developed via surface engineering are applied to a hole transport layer (HTL) in n‐i‐p‐structured perovskite solar cells (PSCs). Hexanoic acid (HA) as a surfactant improves the dispersibility of NiO _x NPs in chlorobenzene (CB). The conductivity of the NiO _x ‐HA film is 1.20×10−5S cm−1, which is superior to that of 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) with dopants. The NiO _x ‐HA film shows better hole extraction properties compared with the pristine NiO _x film. The NiO _x ‐HA NPs form closely packed and pinhole‐free films, leading to improved device performance with a power conversion efficiency from 5.5% to 13.1%.

Eco‐compatible solvent‐processed organic photovoltaic cells with over 16% power conversion efficiency are achieved via modifying the flexible alkyl chains of BTP‐4F‐8. Combining with the polymer donor T1, over 14% power conversion efficiencies are obtained not only for using several kinds of greener solvents like o‐xylene, 1,2,4‐trimethylbenzene, and tetrahydrofuran but also for 1.07 cm² cells by the blade‐coating method.

Abstract

Recent advances in nonfullerene acceptors (NFAs) have enabled the rapid increase in power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells. However, this progress is achieved using highly toxic solvents, which are not suitable for the scalable large‐area processing method, becoming one of the biggest factors hindering the mass production and commercial applications of OPVs. Therefore, it is of great importance to get good eco‐compatible processability when designing efficient OPV materials. Here, to achieve high efficiency and good processability of the NFAs in eco‐compatible solvents, the flexible alkyl chains of the highly efficient NFA BTP‐4F‐8 (also known as Y6) are modified and BTP‐4F‐12 is synthesized. Combining with the polymer donor PBDB‐TF, BTP‐4F‐12 shows the best PCE of 16.4%. Importantly, when the polymer donor PBDB‐TF is replaced by T1 with better solubility, various eco‐compatible solvents can be applied to fabricate OPV cells. Finally, over 14% efficiency is obtained with tetrahydrofuran (THF) as the processing solvent for 1.07 cm² OPV cells by the blade‐coating method. These results indicate that the simple modification of the side chain can be used to tune the processability of active layer materials and thus make it more applicable for the mass production with environmentally benign solvents.

Highly efficient photoluminescence (PL‐QY = 68%), amplified spontaneous emission, and low‐threshold lasing in thin films of cesium lead bromide at room temperature are shown. Importantly, the films are not based on nanocrystals or quantum dots but consist of extended continuous layers, that are formed upon recrystallization of as‐deposited layers by thermal imprint.

Abstract

Cesium lead halide perovskites are of interest for light‐emitting diodes and lasers. So far, thin‐films of CsPbX₃ have typically afforded very low photoluminescence quantum yields (PL‐QY < 20%) and amplified spontaneous emission (ASE) only at cryogenic temperatures, as defect related nonradiative recombination dominated at room temperature (RT). There is a current belief that, for efficient light emission from lead halide perovskites at RT, the charge carriers/excitons need to be confined on the nanometer scale, like in CsPbX₃ nanoparticles (NPs). Here, thin films of cesium lead bromide, which show a high PL‐QY of 68% and low‐threshold ASE at RT, are presented. As‐deposited layers are recrystallized by thermal imprint, which results in continuous films (100% coverage of the substrate), composed of large crystals with micrometer lateral extension. Using these layers, the first cesium lead bromide thin‐film distributed feedback and vertical cavity surface emitting lasers with ultralow threshold at RT that do not rely on the use of NPs are demonstrated. It is foreseen that these results will have a broader impact beyond perovskite lasers and will advise a revision of the paradigm that efficient light emission from CsPbX₃ perovskites can only be achieved with NPs.

A multifunctional chemical linker of 4‐imidazoleacetic acid hydrochloride (ImAcHCl) between SnO₂ and a perovskite layer improves the average power conversion efficiency from 18.60% to 20.22% due to the upward shift of band position, reduced nonradiative recombination, and improved carrier lifetime. In addition, interfacial engineering improves thermal and moisture stability.

Abstract

Chemical interaction at a heterojunction interface induced by an appropriate chemical linker is of crucial importance for high efficiency, hysteresis‐less, and stable perovskite solar cells (PSCs). Effective interface engineering in PSCs is reported via a multifunctional chemical linker of 4‐imidazoleacetic acid hydrochloride (ImAcHCl) that can provide a chemical bridge between SnO₂ and perovskite through an ester bond with SnO₂ via esterification reaction and an electrostatic interaction with perovskite via imidazolium cation in ImAcHCl and iodide anion in perovskite. In addition, the chloride anion in ImAcHCl plays a role in the improvement of crystallinity of perovskite film crystallinity. The introduction of ImAcHCl onto SnO₂ realigns the positions of the conduction and valence bands upwards, reduces nonradiative recombination, and improves carrier life time. As a consequence, average power conversion efficiency (PCE) is increased from 18.60% ± 0.50% to 20.22% ± 0.34% before and after surface modification, respectively, which mainly results from an enhanced voltage from 1.084 ± 0.012 V to 1.143 ± 0.009 V. The best PCE of 21% is achieved by 0.1 mg mL⁻¹ ImAcHCl treatment, along with negligible hysteresis. Moreover, an unencapsulated device with ImAcHCl‐modified SnO₂ shows much better thermal and moisture stability than unmodified SnO₂.

Semi‐transparent perovskite solar cells (ST‐PSCs) have received great attention due to their promising applications in many areas, such as building integrated photovoltaics (BIPV), tandem devices, and wearable electronics. A general overview of recent advances in ST‐PSCs from materials and devices to applications is provided, and presented alongside some personal perspectives on their future development.

Abstract

Semitransparent solar cells (ST‐SCs) have received great attention due to their promising application in many areas, such as building integrated photovoltaics (BIPVs), tandem devices, and wearable electronics. In the past decade, perovskite solar cells (PSCs) have revolutionized the field of photovoltaics (PVs) with their high efficiencies and facile preparation processes. Due to their large absorption coefficient and bandgap tunability, perovskites offer new opportunities to ST‐SCs. Here, a general overview is provided on the recent advances in ST‐PSCs from materials and devices to applications and some personal perspectives on the future development of ST‐PSCs.

Lasing and loss dynamics of mechanically exfoliated, homologous 2D Ruddlesden–Popper perovskite (RPP, (C₄H₉NH₃)₂(CH₃NH₃) _{n −1}Pb _n I_{3 n +1}) crystals are reported. The Auger recombination and the electron–phonon coupling are the major loss channels, and they increase with the decreasing of inorganic layer thickness (n), leading to larger threshold in smaller‐n RPPs, and even the absence of lasing action for n < 3 above 78 K.

Abstract

2D Ruddlesden–Popper perovskites (RPPs) have aroused growing attention in light harvesting and emission applications owing to their high environmental stability. Recently, coherent light emission of RPPs was reported, however mostly from inhomologous thin films that involve cascade intercompositional energy transfer. Lasing and fundamental understanding of intrinsic laser dynamics in homologous RPPs free from intercompositional energy transfer is still inadequate. Herein, the lasing and loss mechanisms of homologous 2D (BA)₂(MA) _{n −1}Pb _n I_{3 n +1} RPP thin flakes mechanically exfoliated from the bulk crystal are reported. Multicolor lasing is achieved from the large‐n RPPs (n ≥ 3) in the spectral range of 620–680 nm but not from small‐n RPPs (n ≤ 2) even down to 78 K. With decreasing n, the lasing threshold increases significantly and the characteristic temperature decreases as 49, 25, and 20 K for n = 5, 4, and 3, respectively. The n‐engineered lasing behaviors are attributed to the stronger Auger recombination and exciton–phonon interaction as a result of the enhanced quantum confinement in the smaller‐n perovskites. These results not only advance the fundamental understanding of loss mechanisms in both inhomologous and homologous RPP lasers but also provide insights into developing low‐threshold, substrate‐free, and multicolor 2D semiconductor microlasers.

High efficiencies of 16.67% (certified as 16.0%) for rigid and 14.06% for flexible organic solar cells (OSCs) are achieved by employing a PM6:Y6:PC₇₁BM ternary system. This is a promising ternary heterojunction strategy for the development of highly efficient rigid and flexible OSCs.

Abstract

Ternary heterojunction strategies appear to be an efficient approach to improve the efficiency of organic solar cells (OSCs) through harvesting more sunlight. Ternary OSCs are fabricated by employing wide bandgap polymer donor (PM6), narrow bandgap nonfullerene acceptor (Y6), and PC₇₁BM as the third component to tune the light absorption and morphologies of the blend films. A record power conversion efficiency (PCE) of 16.67% (certified as 16.0%) on rigid substrate is achieved in an optimized PM6:Y6:PC₇₁BM blend ratio of 1:1:0.2. The introduction of PC₇₁BM endows the blend with enhanced absorption in the range of 300–500 nm and optimises interpenetrating morphologies to promote photogenerated charge dissociation and extraction. More importantly, a PCE of 14.06% for flexible ITO‐free ternary OSCs is obtained based on this ternary heterojunction system, which is the highest PCE reported for flexible state‐of‐the‐art OSCs. A very promising ternary heterojunction strategy to develop highly efficient rigid and flexible OSCs is presented.

Publication date: November 2019

Source: Nano Energy, Volume 65

Author(s): Guoqing Tong, Taotao Chen, Huan Li, Longbin Qiu, Zonghao Liu, Yangyang Dang, Wentao Song, Luis K. Ono, Yang Jiang, Yabing Qi

Graphical abstract

We developed a strategy on the basis of phase transition induced (PTI) crystal rearrangement to fabricate inorganic perovskite solar cells with a high PCE of 10.91% and long-term stability.

Publication date: November 2019

Source: Nano Energy, Volume 65

Author(s): Young Wook Noh, Ju Ho Lee, In Su Jin, Sang Hyun Park, Jae Woong Jung

Graphical abstract

Sn‐based perovskite solar cells (PSCs) with 6.33% power conversion efficiency are fabricated with an aperture area of 1 cm² by introducing a post‐deposition vapor annealing method. The fabricated Sn‐based PSCs show promising stability, both under dark and maximum power‐point tracking conditions.

Sn‐based perovskite solar cells (PSCs) are promising alternatives to replacing toxic Pb‐based PSCs, which have shown a rapid rise in photovoltaic applications in the past 1 year. However, the reported Sn‐based PSCs are often fabricated with a small aperture area (typically 0.02–0.1 cm²) because forming homogeneous pinhole‐free continuous films over a large surface area is still challenging. Herein, a post‐deposition vapor annealing (PDVA) process assisted by methylammonium chloride vapor is presented that enables the fabrication of stable, homogeneous pinhole‐free FASnI₃ perovskite absorber films with low crystal defects and low surface recombination over a relatively large area up to 1.02 cm². Inverted planar solar cells fabricated with a 1.02 cm² aperture area show a maximum power conversion efficiency of 6.33% with high reproducibility and stability. The shelf‐lifetime stability test shows that the PSCs retain 90% of their performance for more than 1000 h when stored in a N₂‐filled glove box and under dark conditions. The preliminary light‐soaking stability tests under continuous illumination and maximum power‐tracking conditions are relatively promising. This study marks an important step toward the up scaling of Sn‐based PSCs.

High‐performance perovskite solar cells with an average power conversion efficiency of 21.4% are achieved based on mixed 2D/3D perovskites with induced phenylethylammonium iodide and exhibit an ultrahigh fill factor (83.6%). The unencapsulated device exhibits enhanced operational stability under continuous simulated sunlight illumination and outstanding air stability after 1000 h of storage under ambient air conditions.

2D/3D perovskite heterostructures or composites are recognized as efficient strategies to improve the stability of perovskite solar cells. Herein, a novel solution process to develop 2D/3D perovskites with modulated diffusion passivation by introducing phenylethylammonium iodide (PEAI) and N,N‐dimethylformamide (DMF) additive, which could effectively enhance device performance and long‐term stability, is demonstrated. Compared with conventional devices, the device with PEAI and DMF solvent additive treatment exhibit enhanced charge transport, improved charge extraction, and suppressed nonradiative carrier recombination. The solar cells with an optimal 2D/3D perovskite passivation treatment exhibit an extremely high fill factor of 83.6% and an average power conversion efficiency of 21.4% (21.3% using integrated photocurrent from the incident photon‐to‐current efficiency spectra) based on the NiO _x hole transport layer. Furthermore, the unencapsulated device exhibits excellent stability under continuously simulated sunlight illumination and outstanding air stability after 1000 h of storage under ambient air conditions.

In article no. 19000108, Wei Wang and Zongping Shao report intrinsically conductive SrCo_0.95P_0.05O_3‐δ (SCP) as a new platinum (Pt)‐free cathode in dye‐sensitized solar cells. SCP shows superior performance compared to the parent SrCoO_3‐δ due to the greatly enhanced electrical conductivity and more internal conducting pathways (Cover illustrator: Yijun Zhong).

In article no. 1900192, Ai Ping Chen, Shuang Yang, Yu Hou, and co‐workers employ a versatile alkaline earth metals doping strategy to engineer the electronic structure of NiO_x contacts for inverted planar perovskite solar cells, in which the champion device demonstrates a power conversion efficiency of 19.49% with a high open circuit voltage of 1.14 V. Alkaline earth metals doping can significantly optimize the electrical properties by deepening the valence band maximum and enhancing the hole conductivity.

In article no. 1900125, Guokun Ma, Hao Wang, and co‐workers use liquid crystal (LC) molecule (4'‐heptyl‐4‐biphenylcarbonitrile) as a binding agent to connect the grain boundaries of perovskites. After treatment with the LC, perovskite crystal growth orientation can be controlled and the electron transport process is accelerated. Remarkably, the LC greatly contributes to the environmental stability of the devices.

In article no. 1900087, Jian‐Qiang Liu, Xiao‐Tao Hao, and co‐workers introduce polypropylene into a bulk heterojunction consisting of donors and acceptors to fabricate effective organic solar cells with a thick active layer. The incorporation of polypropylene improves the crystallinity of the donor and reduces the aggregation size of the acceptor, which facilitates exciton dissociation and charge transition and inhibits the recombination of carriers.

A multifunctional chemical linker of 4‐imidazoleacetic acid hydrochloride (ImAcHCl) between SnO₂ and a perovskite layer improves the average power conversion efficiency from 18.60% to 20.22% due to the upward shift of band position, reduced nonradiative recombination, and improved carrier lifetime. In addition, interfacial engineering improves thermal and moisture stability.

Abstract

Chemical interaction at a heterojunction interface induced by an appropriate chemical linker is of crucial importance for high efficiency, hysteresis‐less, and stable perovskite solar cells (PSCs). Effective interface engineering in PSCs is reported via a multifunctional chemical linker of 4‐imidazoleacetic acid hydrochloride (ImAcHCl) that can provide a chemical bridge between SnO₂ and perovskite through an ester bond with SnO₂ via esterification reaction and an electrostatic interaction with perovskite via imidazolium cation in ImAcHCl and iodide anion in perovskite. In addition, the chloride anion in ImAcHCl plays a role in the improvement of crystallinity of perovskite film crystallinity. The introduction of ImAcHCl onto SnO₂ realigns the positions of the conduction and valence bands upwards, reduces nonradiative recombination, and improves carrier life time. As a consequence, average power conversion efficiency (PCE) is increased from 18.60% ± 0.50% to 20.22% ± 0.34% before and after surface modification, respectively, which mainly results from an enhanced voltage from 1.084 ± 0.012 V to 1.143 ± 0.009 V. The best PCE of 21% is achieved by 0.1 mg mL⁻¹ ImAcHCl treatment, along with negligible hysteresis. Moreover, an unencapsulated device with ImAcHCl‐modified SnO₂ shows much better thermal and moisture stability than unmodified SnO₂.

Nonconjugated multi‐zwitterionic small‐molecule electrolyte (NSE) molecules in perovskite solar cells (PSCs) act not only as both charge‐extracting layers for barrier‐free cathode charge collection but also as charged defect fillers in perovskite bulk and interfaces by spontaneous bottom‐up passivation. Thus, the NSE‐based PSCs deliver PCEs as high as 21.18% with an ultrahigh V _OC of 1.19 V, suppressed hysteresis, and enhanced stability.

Abstract

Recent perovskite solar cell (PSC) advances have pursued strategies for reducing interfacial energetic mismatches to mitigate energy losses, as well as to minimize interfacial and bulk defects and ion vacancies to maximize charge transfer. Here nonconjugated multi‐zwitterionic small‐molecule electrolytes (NSEs) are introduced, which act not only as charge‐extracting layers for barrier‐free charge collection at planar triple cation PSC cathodes but also passivate charged defects at the perovskite bulk/interface via a spontaneous bottom‐up passivation effect. Implementing these synergistic properties affords NSE‐based planar PSCs that deliver a remarkable power conversion efficiency of 21.18% with a maximum V _OC = 1.19 V, in combination with suppressed hysteresis and enhanced environmental, thermal, and light‐soaking stability. Thus, this work demonstrates that the bottom‐up, simultaneous interfacial and bulk trap passivation using NSE modifiers is a promising strategy to overcome outstanding issues impeding further PSC advances.

Semi‐transparent perovskite solar cells (ST‐PSCs) have received great attention due to their promising applications in many areas, such as building integrated photovoltaics (BIPV), tandem devices, and wearable electronics. A general overview of recent advances in ST‐PSCs from materials and devices to applications is provided, and presented alongside some personal perspectives on their future development.

Abstract

Semitransparent solar cells (ST‐SCs) have received great attention due to their promising application in many areas, such as building integrated photovoltaics (BIPVs), tandem devices, and wearable electronics. In the past decade, perovskite solar cells (PSCs) have revolutionized the field of photovoltaics (PVs) with their high efficiencies and facile preparation processes. Due to their large absorption coefficient and bandgap tunability, perovskites offer new opportunities to ST‐SCs. Here, a general overview is provided on the recent advances in ST‐PSCs from materials and devices to applications and some personal perspectives on the future development of ST‐PSCs.

Lasing and loss dynamics of mechanically exfoliated, homologous 2D Ruddlesden–Popper perovskite (RPP, (C₄H₉NH₃)₂(CH₃NH₃) _{n −1}Pb _n I_{3 n +1}) crystals are reported. The Auger recombination and the electron–phonon coupling are the major loss channels, and they increase with the decreasing of inorganic layer thickness (n), leading to larger threshold in smaller‐n RPPs, and even the absence of lasing action for n < 3 above 78 K.

Abstract

2D Ruddlesden–Popper perovskites (RPPs) have aroused growing attention in light harvesting and emission applications owing to their high environmental stability. Recently, coherent light emission of RPPs was reported, however mostly from inhomologous thin films that involve cascade intercompositional energy transfer. Lasing and fundamental understanding of intrinsic laser dynamics in homologous RPPs free from intercompositional energy transfer is still inadequate. Herein, the lasing and loss mechanisms of homologous 2D (BA)₂(MA) _{n −1}Pb _n I_{3 n +1} RPP thin flakes mechanically exfoliated from the bulk crystal are reported. Multicolor lasing is achieved from the large‐n RPPs (n ≥ 3) in the spectral range of 620–680 nm but not from small‐n RPPs (n ≤ 2) even down to 78 K. With decreasing n, the lasing threshold increases significantly and the characteristic temperature decreases as 49, 25, and 20 K for n = 5, 4, and 3, respectively. The n‐engineered lasing behaviors are attributed to the stronger Auger recombination and exciton–phonon interaction as a result of the enhanced quantum confinement in the smaller‐n perovskites. These results not only advance the fundamental understanding of loss mechanisms in both inhomologous and homologous RPP lasers but also provide insights into developing low‐threshold, substrate‐free, and multicolor 2D semiconductor microlasers.