Ligang Yuan

Small amounts of bromide incorporation in the triple cation tin-based perovskite solar cells enhance the vertical orientation of the perovskite film as well as suppress the tin oxidation in the film, resulting in a high power conversion efficiency (10.12%) with outstanding stability.

Tin-halide perovskite solar cells (THPSCs) are attractive in the photovoltaic field as promising candidates to address the issue of potential lead toxicity and approach the theoretical efficiency limit in lead-halide perovskite photovoltaics. Nevertheless, THPSCs suffer from fast crystallization, low defect tolerance, mismatched energy levels, as well as severe oxidation from Sn²⁺ to Sn⁴⁺, leading to the low performance of devices. Herein, bromide is incorporated in the PEA_0.15EA_0.15FA_0.70SnI_1−X Br _X perovskite precursor, which produces 2D/3D hybrid cations tin-halide perovskite films with highly vertical oriented crystallization, favorable band-level alignment, and suppressed tin oxidation. This leads to the decrease of trap density and charge recombination losses and the enhancement of charge carrier extraction in THPSCs. Consequently, the power conversion efficiency of the optimal THPSC (X = 0.30) surges to 10.12% in contrast to 7.13% of the control device (X = 0.00), along with a nearly eliminated current–voltage hysteresis. Furthermore, bromine-incorporated THPSCs exhibit outstanding light soaking and humidity stability. These results are also in good agreement with the density functional theory calculations. This compositional engineering with Br could become a promising approach for improving the efficiency and stability of THPSCs.

Orderly oxidation of CsPbI₂Br film in moist air leads to more efficient defect passivation in film by grain boundary oxidation, and higher hole extraction efficiency in device via the energy band coupling between CsPbI₂Br and oxidation product CsPbIBr₂. The champion cell achieves an efficiency of 15.27%, and a certified efficiency of 14.7%, which is a record efficiency for CsPbI₂Br C-PSCs.

Abstract

Large energy loss (E _loss) caused by defect-assisted recombination makes the photovoltaic performance of carbon-based perovskite solar cells (C-PSCs) inferior to that of metal-electrode ones. Herein, the influence of environmental factors (moisture and oxygen) on defect management during re-annealing process of CsPbI₂Br crystalline films is systematically studied. Density functional theory and experimental results indicate that moisture in the air can significantly reduce the oxidation kinetics of crystalline films, resulting in orderly oxidation. Concomitantly, the oxidation decomposition products PbO and CsPbIBr₂ are enriched at grain boundaries, passivating surface defects efficiently. Simultaneously, energy band coupling between CsPbI₂Br and CsPbIBr₂ improves the hole extraction efficiency. The photovoltage of corresponding C-PSCs is increased from 1.05 to 1.32 V, indicating a reduced E _loss derived from orderly oxidation strategy. Correspondingly, the champion cell achieves an efficiency of 15.27%, and a certified efficiency of 14.7%, which is a new record efficiency for CsPbI₂Br C-PSCs.

Donor alloy strategy is proposed to tune chare transfer (CT) state erergy and thus E _loss for boosting organic solar cells (OSCs) efficiency. Together with optimal morphology, ternary OSCs deliver an outstanding efficiency of 19.22% with significantly improved open-circuit voltage (V _oc) of 0.910 V, the highest value for over 19% efficiency OSCs.

Abstract

The large energy loss (E _loss) is one of the main obstacles to further improve the photovoltaic performance of organic solar cells (OSCs), which is closely related to the charge transfer (CT) state. Herein, ternary donor alloy strategy is used to precisely tune the energy of CT state (E _CT) and thus the E _loss for boosting the efficiency of OSCs. The elevated E _CT in the ternary OSCs reduce the energy loss for charge generation (ΔE _CT), and promote the hybridization between localized excitation state and CT state to reduce the nonradiative energy loss (ΔE _nonrad). Together with the optimal morphology, the ternary OSCs afford an impressive power conversion efficiency of 19.22% with a significantly improved open-circuit voltage (V _oc) of 0.910 V without sacrificing short-cicuit density (J _sc) and fill factor (FF) in comparison to the binary ones. This contribution reveals that precisely tuning the E _CT via donor alloy strategy is an efficient way to minimize E _loss and improve the photovoltaic performance of OSCs.

Nature Energy, Published online: 29 August 2022; doi:10.1038/s41560-022-01102-w

Scaling up all-perovskite tandem solar modules is challenging due to the degradation of the low-bandgap subcell during processing in ambient conditions. Here Dai et al. devise an additive- and hot gas-assisted blade-coating process that enables modules with 21.6% efficiency over an aperture area of 14.3 cm2.

A synergistic bulk passivation and interface modification strategy is developed for the fabrication of high-quality tin–lead mixed perovskite films (1.27 eV) and efficient solar devices by blade-coating. Owing to the significantly suppressed nonradiative charge recombination, the prepared solar cells give a high efficiency of 19.06% with an impressive open-circuit voltage of 0.837 V.

Thin films of tin–lead alloyed perovskites are drawing growing attention, mainly owing to their tunable bandgaps in delivering efficient single- and multi-junction photovoltaic devices. The rapid efficiency advancement of Sn–Pb perovskite devices has been dependent primarily on improving the crystal quality of perovskite films via retarding oxidation of Sn²⁺. Herein, it is demonstrated that in addition to obtaining high-quality Sn–Pb perovskite thin films, reducing nonradiative recombination losses at interfaces is equally important for realizing efficient solar cells. An aromatic amine is first introduced to passivate the grain boundary in printed Sn–Pb perovskite films, which boosts the open-circuit voltage (V _OC) of the solar devices from 700 to 766 mV. Further enhancement of the V _OC to 814 mV and finally to 837 mV is realized by forming a 2D/3D-layered heterojunction and doping the hole extraction layer with a polyelectrolyte, respectively, benefiting from the largely suppressed nonradiative recombination losses at interfaces. Eventually, the mixed Sn–Pb perovskite devices with a bandgap of ≈1.27 eV yield a high efficiency of 19.06% and in parallel show improved shelf and light-soaking stability.

Modulation of film formation kinetics has paved the way for developing deep-blue emissive quasi-2D perovskites. A universal synthetic strategy, potentially applicable to various material systems, is introduced to narrow the width distribution of perovskite quantum wells. The controlled and simultaneous evaporation of solvent and antisolvent is key.

Abstract

Solution-processed quasi-2D perovskites contain multiple quantum wells with a broad width distribution. Inhomogeneity results in the charge funneling into the smallest bandgap components, which hinders deep-blue emission and accelerates Auger recombination. Here, a synthetic strategy applied to a range of quasi-2D perovskite systems is reported, that significantly narrows the quantum well dispersity. It is shown that the phase distribution in the perovskite film is significantly narrowed with controlled, simultaneous evaporation of solvent and antisolvent. Modulation of film formation kinetics of quasi-2D perovskite enables stable deep-blue electroluminescence with a peak emission wavelength of 466 nm and a narrow linewidth of 14 nm. Light emitting diodes using the perovskite film show a maximum luminance of 280 cd m^–2 at an external quantum efficiency of 0.1%. This synthetic approach will serve in producing new materials widening the color gamut of next-generation displays.

New synthesized non-conjugated polyelectrolyte is introduced as an interfacial layer between the charge-transport layer and perovskite absorbent, which significantly reduce both bulk and interfacial nonradiative recombination losses, but also aligns the interface's energy level. The modified perovskite solar cells show a power conversion efficiency of 24.4% (open-circuit voltage 1.21 V) with negligible hysteresis and superior operational stability.

Abstract

Suppressing nonradiative recombination at the interface between the organometal halide perovskite (PVK) and the charge-transport layer (CTL) is crucial for improving the efficiency and stability of PVK-based solar cells (PSCs). Here, a new bathocuproine (BCP)-based nonconjugated polyelectrolyte (poly-BCP) is synthesized and this is introduced as a “dual-side passivation layer” between the tin oxide (SnO₂) CTL and the PVK absorber. Poly-BCP significantly suppresses both bulk and interfacial nonradiative recombination by passivating oxygen-vacancy defects from the SnO₂ side and simultaneously scavenges ionic defects from the other (PVK) side. Therefore, PSCs with poly-BCP exhibits a high power conversion efficiency (PCE) of 24.4% and a high open-circuit voltage of 1.21 V with a reduced voltage loss (PVK bandgap of 1.56 eV). The non-encapsulated PSCs also show excellent long-term stability by retaining 93% of the initial PCE after 700 h under continuous 1-sun irradiation in nitrogen atmosphere conditions.

A strain modulation strategy to constrain phase segregation in a wide-bandgap perovskite absorber by reinforcing the energy barrier for ion migration is reported. With compressive strain, the single-junction devices yield one of smallest voltage deficits of 440 mV. Moreover, the resulting perovskite/silicon tandem solar cells achieve a champion efficiency of 26.95% with improved light stability at open-circuit.

Abstract

Perovskite/silicon tandem solar cells are promising to penetrate photovoltaic market. However, the wide-bandgap perovskite absorbers used in top-cell often suffer severe phase segregation under illumination, which restricts the operation lifetime of tandem solar cells. Here, a strain modulation strategy to fabricate light-stable perovskite/silicon tandem solar cells is reported. By employing adenosine triphosphate, the residual tensile strain in the wide-bandgap perovskite absorber is successfully converted to compressive strain, which mitigates light-induced ion migration and phase segregation. Based on the wide-bandgap perovskite with compressive strain, single-junction solar cells with the n–i–p layout yield a power conversion efficiency (PCE) of 20.53% with the smallest voltage deficits of 440 mV. These cells also maintain 83.60% of initial PCE after 2500 h operation at the maximum power point. Finally, these top cells are integrated with silicon bottom cells in a monolithic tandem device, which achieves a PCE of 26.95% and improved light stability at open-circuit.

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.

Efficient indoor photovoltaics are achieved with wide bandgap metal halide perovskites. The optimal bandgap is first predicted with detailed balanced theory. The non-radiative recombination losses of the mixed-halide perovskites are reduced with both passivation in the bulk and interface with Pb(SCN)₂ and PEABr, respectively, which result in extremely high power conversion efficiency and open-circuit voltage under weak light illumination.

Abstract

Indoor photovoltaics have attracted increasing attention, since they can provide sustainable energy through the recycling of photon energy from household dim lighting. However, solar cells exhibiting high performance under sunlight may not perform well under indoor light conditions, mainly due to the mismatch of the irradiance spectrum. In particular, most of the indoor light sources emit visible photons with negligible near-infrared irradiance. According to the detailed balance theory, the optimal bandgap for indoor photovoltaics should be relatively larger, considering the trade-off between photocurrent and photovoltage losses. In this work, a systematic comparison of the theoretical limits of the conventional and indoor photovoltaics is presented. Then the non-radiative recombination losses are reduced by a synergetic treatment with Pb(SCN)₂ and PEABr, resulting relatively high open circuit voltage of 1.29 V and power conversion efficiency of 17.32% under 1 sun illumination. Furthermore, the devices are fully characterized under weak indoor light (1000 lux, 4000 K LED) achieving a high efficiency of 37.18%, which is promising for real applications.

Publication date: 15 October 2022

Source: Chemical Engineering Journal, Volume 446, Part 2

Author(s): Jiarong Wang, Ligang Yuan, Huiming Luo, Chenghao Duan, Biao Zhou, Qiaoyun Wen, Keyou Yan

Publication date: 18 May 2022

Source: Joule, Volume 6, Issue 5

Author(s): Minhuan Wang, Yepin Zhao, Xiaoqing Jiang, Yanfeng Yin, Ilhan Yavuz, Pengchen Zhu, Anni Zhang, Gill Sang Han, Hyun Suk Jung, Yifan Zhou, Wenxin Yang, Jiming Bian, Shengye Jin, Jin-Wook Lee, Yang Yang

Publication date: 15 September 2022

Source: Chemical Engineering Journal, Volume 444

Author(s): Zhen-Li Yan, Fang-Cheng Liang, Chia-Yu Yeh, Darwin Kurniawan, Jean-Sebastien Benas, Wei-Cheng Chen, Chia‐Jung Cho, Wei-Hung Chiang, Ru-Jong Jeng, Chi-Ching Kuo

Publication date: 15 September 2022

Source: Chemical Engineering Journal, Volume 444

Author(s): Wei-Min Gu, Ke-Jian Jiang, Fengting Li, Guang-Hui Yu, Yanting Xu, Xin-Heng Fan, Cai-Yan Gao, Lian-Ming Yang, Yanlin Song

Publication date: 15 August 2022

Source: Chemical Engineering Journal, Volume 442, Part 2

Author(s): Zhihong Yin, Xia Guo, Yang Wang, Lei Zhu, Yuhao Chen, Qunping Fan, Jianqiu Wang, Wenyan Su, Feng Liu, Maojie Zhang, Yongfang Li

An environmental-friendly PBAT polymer is adopted to implant the perovskite film with an anti-solvent method, which can passivate the uncoordinated Pb²⁺ and neutral iodine defects of perovskite material and markedly improve device efficiency and operational stability. More importantly, the polymer network can prevent nearly 98% of Pb²⁺ from leaking by directly immersing the polymer-coated perovskite film in water.

Abstract

Although perovskite solar cells (PSCs) are on the road to industrialization, the operational stability under high efficiency still needs to be improved, and the water solubility of lead ions (Pb²⁺) will cause environmental pollution problems. Herein, it is successfully implanted an environment-friendly (biodegradability) poly(butylene adipate-coterephthalate) polymer (PBAT) into the perovskite film, which can passivate the uncoordinated Pb²⁺ and neutral iodine defects of the perovskite material because of the adequate carbonyl groups and benzene rings in PBAT polymer, thereby regulating the crystallization of perovskite film with lower trap density, inhibiting the nonradiative recombination and improving charge carrier transport. As a result, the polymer-incorporated inverted PSCs achieve optimal conversion efficiencies of 22.07% (0.1 cm²) and 20.31% (1 cm²). Meanwhile, the incorporated device, after being encapsulated, exhibits a prominent improvement in operational stability of high-efficiency device under maximum power point tracking and continuous one sunlight illumination, maintaining the initial efficiency of 80% for 3249 h. More importantly, the polymer network can protect Pb²⁺ from being dissolved by water and prevent nearly 98% of Pb²⁺ from leaking by directly immersing the polymer-coated perovskite film in water. Environmental-friendly molecules provide new hope for solving lead poisoning and improving device operational stability under high efficiency.

Nature, Published online: 13 April 2022; doi:10.1038/s41586-022-04455-0

A thin low-loss indium oxide interconnect layer grown by atomic layer deposition enables perovskite–organic hybrid tandem solar cells with a high open-circuit voltage and a high power conversion efficiency.

A two-step orthogonal solvent method that enables straightforward fabrication of multilayer perovskite films is applied to construct the perovskite/carbon heterojunction for carbon-based perovskite solar cells (PSCs). Such a bulk heterojunction (BHJ) improves the interface contact and facilitates the hole transport between perovskite and the carbon electrode, significantly boosting the power conversion efficiency (PCE) to 16.4% with certification.

An efficient perovskite junction is critical for the functioning of perovskite solar cells (PSCs). However, carbon-based perovskite solar cells (C-PSCs) have been plagued by the paucity of ways to construct an efficient junction between perovskite and carbon, staggering around an efficiency much lower than other state-of-the-art PSCs. Herein, a perovskite/carbon bulk heterojunction (BHJ) for C-PSCs is innovated and systematically studied. First, a two-step orthogonal solvent method is developed to deposit a series of high-quality perovskite films directly on the preformed perovskite film, allowing to manipulate compositions, band alignment, and charge transfer of the perovskite junction in a low-cost and straightforward fashion. Second, by adopting this method to a porous carbon electrode as originally motivated, fabrication of perovskite/carbon BHJ with perovskite crystals by seamlessly filling in the porous carbon film is successfully done, thus providing a high contact area of perovskite/carbon heterojunction. Such a BHJ accelerates hole collection of the carbon electrode from the perovskite layer, thus significantly boosting the performance of C-PSCs with MAPbI₃ as the active layer from 12% to over 16% with certification. The device is shown to be stable with no obvious degradation after 1700 h of continuous light soaking near the maximum power point.

Publication date: 20 April 2022

Source: Joule, Volume 6, Issue 4

Author(s): Jiwei Liang, Xuzhi Hu, Chen Wang, Chao Liang, Cong Chen, Meng Xiao, Jiashuai Li, Chen Tao, Guichuan Xing, Rui Yu, Weijun Ke, Guojia Fang

Publication date: 15 August 2022

Source: Chemical Engineering Journal, Volume 442, Part 2

Author(s): Hongru Ma, Minhuan Wang, Yudi Wang, Qingshun Dong, Jing Liu, Yanfeng Yin, Jie Zhang, Mingzhu Pei, Linghui Zhang, Wanxian Cai, Lei Shi, Wenming Tian, Shengye Jin, Jiming Bian, Yantao Shi