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270. "Device performance of emerging photovoltaic materials (Version 3)"
         Osbel Almora, Derya Baran, Guillermo C Bazan, Carlos I Cabrera, Sule Erten‐Ela, Karen Forberich, Fei Guo, Jens Hauch,               Anita WY Ho‐Baillie, T Jesper Jacobsson, Rene AJ Janssen, Thomas Kirchartz, Nikos Kopidakis, Maria A Loi, Richard R

         Lunt, Xavier Mathew, Michael D McGehee, Jie Min, David B Mitzi, Mohammad K Nazeeruddin, Jenny Nelson, Ana F                         Nogueira, Ulrich W Paetzold, Barry P Rand, Uwe Rau, Henry J Snaith, Eva Unger, Lídice Vaillant‐Roca, Chenchen Yang,

         Hin‐Lap Yip, Christoph J Brabec
        Advanced Energy Materials,  2023,











Following the 2nd release of the “Emerging PV reports,” the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2021. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open-circuit voltage, short-circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application, and are put into perspective using, e.g., the detailed balance efficiency limit. The 3rd installment of the “Emerging PV reports” extends the scope toward triple junction solar cells.


271. "Dual Sub-Cells Modification Enables High-Efficiency n–i–p Type Monolithic Perovskite/Organic Tandem Solar Cells"
         Qin Yao, Yue‐Min Xie, Yingzhi Zhou, Qifan Xue, Xin Xu, Yujia Gao, Tianqi Niu, Linghao Chu, Zhisheng Zhou, Francis R Lin,               Alex K‐Y Jen, Tingting Shi, Hin‐Lap Yip, Yong Cao
        Advanced Functional Materials,  2023,













Monolithic perovskite/organic tandem solar cells (POTSCs) have attracted increasing attention owing to ability to overcome the Shockley–Queisser limit. However, compromised sub-cells performance limits the tandem device performance, and the power conversion efficiency (PCE) of POTSCs is still lower than their single-junction counterparts. Therefore, optimized sub-cells with minimal energy loss are desired for producing high-efficiency POTSCs. In this study, an ionic liquid, methylammonium acetate (MAAc), is used to modify wide-bandgap perovskite sub-cells (WPSCs), and bathocuproine (BCP) is used to modify small-bandgap organic solar cells. The Ac− group of MAAc can effectively heal the Pb defects in the all-inorganic perovskite film, which enables a high PCE of 17.16% and an open-circuit voltage (Voc) of 1.31 V for CsPbI2.2Br0.8-based WPSCs. Meanwhile, the BCP film, inserted at the ZnO/organic bulk-heterojunction (BHJ) interface, acts as a space layer to prevent direct contact between ZnO and the BHJ while passivating the surface defects of ZnO, thereby mitigating ZnO defect-induced efficiency loss. As a result, PM6:CH1007-based SOSCs exhibit a PCE of 15.46%. Integrating these modified sub-cells enable the fabrication of monolithic n–i–p structured POTSCs with a maximum PCE of 22.43% (21.42% certified), which is one of the highest efficiencies in such type of POTSCs.


272. "Roadmap on Commercialization of Metal Halide Perovskite Photovoltaics"
         Shien-Ping Feng, Yuanhang Cheng, Hin-Lap Yip, Yufei Zhong, Patrick WK Fong, Gang Li, Annie Ng, Cong Chen, Luigi Angelo           Castriotta, Fabio Matteocci, Luigi Vesce, Danila Saranin, Aldo Di Carlo, Puqun Wang, Jian Wei Ho, Yi Hou, Fen Lin, Armin                 Gerhard Aberle, Zhaoning Song, Yanfa Yan, Xu Chen, Yang Michael Yang, Ali Ashgar Syed, Ishaq Ahmad, Tik Lun Leung,                 Yantao Wang, JingYang Lin, Alan MC Ng, Yin Li, Firouzeh Ebadi, Wolfgang Tress, Giles Richardson, Chuangye Ge,

         Hanlin Hu, Masoud Karimipour, Fanny Amanda Karolina Baumann, Kenedy Tabah Tanko, Carlos Pereyra, Sonia Raga,                     Haibing Xie, Monica Lira-Cantu, Mark V Khenkin, Iris Visoly-Fisher, Eugene A Katz, Yana Vaynzof, Rosario Vidal,

         Guicheng Yu, Haorin Lin,  Shuchen Weng, Shifeng Wang, Aleksandra B Djurisic
        Journal of Physics: Materials,  2023, DOI 10.1088/2515-7639/acc893













Perovskite solar cells represent one of the most promising emerging photovoltaic technologies due to their high power conversion efficiency. However, despite of the huge progress made not only in terms of the efficiency achieved, but also fundamental understanding of relevant physics of the devices and issues which affect their efficiency and stability, there are still unresolved problems and obstacles on the path towards commercialization of this promising technology. In this roadmap, we aim to provide a concise and up to date summary of outstanding issues and challenges, and progress made towards addressing these issues. While the format of this article is not meant to be a comprehensive review of the topic, it provides a collection of the viewpoints of the experts in the field which covers a broad range of topics related to perovskite solar cell commercialization, including those relevant for manufacturing (scaling up, different types of devices), operation and stability (various factors), and environmental issues (in particular the use of lead). We hope that the article will provide a useful resource for researchers in the field and that it will facilitate discussions and moving forward towards addressing the outstanding challenges in this fast developing field.


273. "All‐Inorganic Perovskite‐Based Monolithic Perovskite/Organic Tandem Solar Cells with 23.21% Efficiency by Dual‐Interface Engineering"
         Shuang‐Qiao Sun, Xiuwen Xu, Qi Sun, Qin Yao, Yating Cai, Xin‐Yi Li, Yan‐Lin Xu, Wei He, Min Zhu, Xuan Lv, Francis R Lin,               Alex K‐Y Jen, Tingting Shi, Hin‐Lap Yip, Man‐Keung Fung, Yue‐Min Xie
        Advanced Energy Materials,  2023,







Monolithic perovskite/organic tandem solar cells (POTSCs) have significant advantages in next-generation flexible photovoltaics, owing to their capability to overcome the Shockley–Queisser limit and facile device integration. However, the compromised sub-cells performance challenges the fabrication of high-efficiency POTSCs. Especially for all-inorganic wide-bandgap perovskite front sub-cells (AIWPSCs) based n-i-p structured POTSCs (AIPOTSCs), for which the power conversion efficiency (PCE) is much lower than organic–inorganic mixed-halide wide-bandgap perovskite based POTSCs. Herein, an ionic liquid, methylammonium formate (MAFm), based dual-interface engineering approach is developed to modify the bottom and top interfaces of wide-bandgap CsPbI2Br films. In particular, the Fm− group of MAFm can effectively passivate the interface defects, and the top interface modification can facilitate the formation of uniform perovskite films with enlarged grain size, thereby mitigating the defects and perovskite grain boundaries induced carrier recombination. As a result, CsPbI2Br-based AIWPSCs with a high PCE of 17.0% and open-circuit voltage (VOC) of 1.347 V are achieved. By integrating these dual-interface engineered CsPbI2Br-based front sub-cells with the narrow-bandgap PM6:CH1007-based rear sub-cells, a record PCE of 23.21% is obtained for AIPOTSCs, illustrating the potential of AIPOTSCs for achieving high-efficiency tandem solar cells.


274. "Deciphering the Roles of MA-Based Volatile Additives for α-FAPbI3 to Enable Efficient Inverted Perovskite Solar Cells"
         Leyu Bi, Qiang Fu, Zixin Zeng, Yunfan Wang, Francis R Lin, Yuanhang Cheng, Hin-Lap Yip, Sai Wing Tsang, Alex K-Y Jen
        Journal of the American Chemical Society,  2023,




Functional additives that can interact with the perovskite precursors to form the intermediate phase have been proven essential in obtaining uniform and stable α-FAPbI3 films. Among them, Cl-based volatile additives are the most prevalent in the literature. However, their exact role is still unclear, especially in inverted perovskite solar cells (PSCs). In this work, we have systematically studied the functions of Cl-based volatile additives and MA-based additives in formamidinium lead iodide (FAPbI3)-based inverted PSCs. Using in situ photoluminescence, we provide clear evidence to unravel the different roles of volatile additives (NH4Cl, FACl, and MACl) and MA-based additives (MACl, MABr, and MAI) in the nucleation, crystallization, and phase transition of FAPbI3. Three different kinds of crystallization routes are proposed based on the above additives. The non-MA volatile additives (NH4Cl and FACl) were found to promote crystallization and lower the phase-transition temperatures. The MA-based additives could quickly induce MA-rich nuclei to form pure α-phase FAPbI3 and dramatically reduce phase-transition temperatures. Furthermore, volatile MACl provides a unique effect on promoting the growth of secondary crystallization during annealing. The optimized solar cells with MACl can achieve an efficiency of 23.1%, which is the highest in inverted FAPbI3-based PSCs.


275. "Correlation of Local Isomerization Induced Lateral and Terminal Torsions with Performance and Stability of Organic                           Photovoltaics"
         Baobing Fan, Wei Gao, Rui Zhang, Werner Kaminsky, Francis R Lin, Xinxin Xia, Qunping Fan, Yanxun Li, Yidan An, Yue Wu,             Ming Liu, Xinhui Lu, Wen Jung Li, Hin-Lap Yip, Feng Gao, Alex K-Y Jen
        Journal of the American Chemical Society,  2023,




Organic photovoltaics (OPVs) have achieved great progress in recent years due to delicately designed non-fullerene acceptors (NFAs). Compared with tailoring of the aromatic heterocycles on the NFA backbone, the incorporation of conjugated side-groups is a cost-effective way to improve the photoelectrical properties of NFAs. However, the modifications of side-groups also need to consider their effects on device stability since the molecular planarity changes induced by side-groups are related to the NFA aggregation and the evolution of the blend morphology under stresses. Herein, a new class of NFAs with local-isomerized conjugated side-groups are developed and the impact of local isomerization on their geometries and device performance/stability are systematically investigated. The device based on one of the isomers with balanced side- and terminal-group torsion angles can deliver an impressive power conversion efficiency (PCE) of 18.5%, with a low energy loss (0.528 V) and an excellent photo- and thermal stability. A similar approach can also be applied to another polymer donor to achieve an even higher PCE of 18.8%, which is among the highest efficiencies obtained for binary OPVs. This work demonstrates the effectiveness of applying local isomerization to fine-tune the side-group steric effect and non-covalent interactions between side-group and backbone, therefore improving both photovoltaic performance and stability of fused ring NFA-based OPVs.





Wide-bandgap perovskite sub-cells (WPSCs)-based tandem solar cells attract considerable interest because of their capability to surpass the Shockley–Queisser limit. Monolithic perovskite/organic tandem solar cells (POTSCs) integrating WPSCs and small-bandgap organic sub-cells (SOSCs) are famous compositions owing to their simple fabrication method and compatibility with flexible devices. Most studies on POTSCs focus on enhancing device efficiency by modifying one or two of the device components (WPSCs, SOSCs, and interconnecting layers). The characteristics of POTSCs are not extensively investigated so far, especially in terms of the influence of the device structure and component properties on the tandem device photovoltaic performance. In this study, the existing p–i–n type WPSC-based p–i–n POTSCs and n–i–p type WPSC-based n–i–p POTSCs are reviewed and their advantages and limitations are highlighted. Furthermore, the influence of the tandem device component properties (optical, electrical, and photovoltaic properties) on the photovoltaic parameters (open-circuit voltage, short-circuit current density, fill factor, and power conversion efficiency) and the existing device modification methods are discussed to provide comprehensive guidance for the development of POTSCs.


277. "Intermolecular CT excitons enable nanosecond excited-state lifetimes in NIR-absorbing non-fullerene acceptors for efficient             organic solar cells"
         Xian-Kai Chen, Christopher Chan, Sudhi Mahadevan, Yu Guo, Guichuan Zhang, He Yan, Kam Sing Wong, Hin-Lap Yip, Jean-           Luc Bredas, Sai Wing Tsang, Philip CY Chow
        arXiv preprint arXiv:2304.09408,  2023,









State-of-the-art Y6-type molecular acceptors exhibit nanosecond excited-state lifetimes despite their low optical gaps (~1.4 eV), thus allowing organic solar cells (OSCs) to achieve highly efficient charge generation with extended near-infrared (NIR) absorption range (up to ~1000 nm). However, the precise molecular-level mechanism that enables low-energy excited states in Y6-type acceptors to achieve nanosecond lifetimes has remained elusive. Here, we demonstrate that the distinct packing of Y6 molecules in film leads to a strong intermolecular charge-transfer (iCT) character of the lowest excited state in Y6 aggregates, which is absent in other low-gap acceptors such as ITIC. Due to strong electronic couplings between the adjacent Y6 molecules, the iCT-exciton energies are greatly reduced by up to ~0.25 eV with respect to excitons formed in separated molecules. Importantly, despite their low energies, the iCT excitons have reduced non-adiabatic electron-vibration couplings with the electronic ground state, thus suppressing non-radiative recombination and allowing Y6 to overcome the well-known energy gap law. Our results reveal the fundamental relationship between molecular packing and nanosecond excited-state lifetimes in NIR-absorbing Y6-type acceptors underlying the outstanding performance of Y6-based OSCs.

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