Key Takeaways & Executive Findings
- •• Li2CO3 modification of SnO2 electron transport layer enables dual interfacial passivation, reducing Voc loss in HTL-free carbon-based perovskite solar cells. • The dual passivation mechanism involves enhanced charge extraction and optimized energy alignment at the ETL/perovskite interface, plus PbI2-induced defect suppression at the perovskite top surface. • The optimized C-PSC achieves a high PCE of 19.1% under standard illumination and a record-high PCE of 33.2% under indoor LED light (2000 lx, 3000 K). • This work provides a practical, low-cost approach to fabricate highly efficient carbon-based perovskite solar cells for indoor photovoltaic applications.
Abstract
The hole transport layer (HTL)-free carbon-based perovskite solar cells (C-PSCs) are promising for commercialization owing to their excellent operational stability and simple fabrication process. However, the power conversion efficiencies (PCE) of C-PSCs are inferior to the metal electrode-based devices due to their open-circuit voltage (Voc) loss. Herein, time-resolved confocal photoluminescence microscopy reveals that grain boundary defects at the perovskite/carbon interface are very likely to function as nonradiative recombination centers in HTL-free C-PSCs. A versatile additive Li2CO3 is used to modify the conformal tin oxide electron transport layer for HTL-free C-PSCs. Li2CO3 modification can result in enhanced charge extraction and optimized energy alignment at electron transport layer/perovskite interface, as well as suppressed defects at perovskite top surface due to Li2CO3-induced formation of PbI2 crystallites. Such dual interfacial passivation ultimately leads to significantly improved Voc up to 1.142 V, which is comparable to the metal electrode-based devices with HTL. Moreover, a record-high PCE of 33.2% is achieved for Li2CO3-modified C-PSCs under weak light illumination conditions, demonstrating excellent indoor photovoltaic performance. This work provides a practical approach to fabricate low-cost, highly efficient carbon-based perovskite solar cells.
1. Introduction
Organic–inorganic hybrid perovskite solar cells (PSCs) have been outstanding among the next-generation photovoltaic technologies in the past decade due to their ease of fabrication and excellent photovoltaic properties, such as high optical absorption coefficients, long carrier diffusion length, and low exciton binding energy [1–5]. The certified power conversion efficiencies (PCE) of PSCs have reached up to 27.0% [6], which is close to the efficiencies achieved by the best-performing monocrystalline silicon solar cells. While the soaring efficiencies make these technologies highly attractive for future commercialization, the long-term stability of PSCs remains a major concern for their practical applications [7–10].
Hole transport layer (HTL)-free carbon-based perovskite solar cells (C-PSCs) are considered as a promising candidate for commercialization due to their extraordinary operational stability and cost-effective fabrication processes [11–15]. However, the PCE of HTL-free C-PSCs lags significantly behind those of the PSCs with HTL, accompanied with severe open-circuit voltage (Voc) loss [15–17]. Several strategies have been employed to improve the efficiency of HTL-free C-PSCs, for instance, enhancing electron/hole extraction [13], optimizing energy alignment [18, 19], passivating interfacial trap states [10, 20–22], and suppressing ion migration [23]. One of the primary reasons for the large Voc loss in the HTL-free C-PSCs is the nonradiative recombination at both top and buried bottom interfaces. Many previous studies on HTL-free C-PSCs have been focusing on the interface of perovskite absorbers and carbon electrodes [14, 18, 24, 25]. For instance, enhanced interfacial energy-level alignment in the HTL-free C-PSCs can be achieved by depositing a thin layer of poly(ethylene oxide) at the perovskite/carbon interface, and the optimized devices showed an increased PCE from 12.2% to 14.9% [18]. Employing a 2D perovskite passivating layer as an electron blocking layer (EBL) atop the 3D perovskite absorber has also been demonstrated to substantially suppress the interfacial recombination loss [26, 27]. For example, an octylammonium-based 2D perovskite EBL can effectively passivate the surface trap states and block the undesirable electron transfer, which enables HTL-free C-PSCs with a PCE of 18.5% and a Voc of 1.05 V [14]. Furthermore, an optimal balance between defect passivation, energy-level structure, and
Loading authentic research manuscript (Pages 1–5)...
Xian Zhang, Fangzhou Liu, Yan Guan, Yu Zou, Cuncun Wu, Dongchang Shi, Hongkai Zhang, Wenjin Yu, Dechun Zou, Yangyang Zhang, Lixin Xiao, Shijian Zheng (2025). Reducing the Voc Loss of Hole Transport Layer-Free Carbon-Based Perovskite Solar Cells via Dual Interfacial Passivation. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01775-4
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the main challenge addressed in this paper?
The main challenge is the significant open-circuit voltage (Voc) loss in hole transport layer-free carbon-based perovskite solar cells (C-PSCs), which limits their power conversion efficiency compared to metal electrode-based devices.
How does Li2CO3 modification improve the performance of C-PSCs?
Li2CO3 modification of the SnO2 electron transport layer enhances charge extraction and optimizes energy alignment at the ETL/perovskite interface. Additionally, it induces the formation of PbI2 crystallites at the perovskite top surface, which passivates grain boundary and surface defects, leading to reduced nonradiative recombination and increased Voc.
What are the key performance metrics achieved in this study?
The Li2CO3-modified C-PSC achieves a power conversion efficiency (PCE) of 19.1% with a Voc of 1.142 V under standard illumination. Under weak LED light (2000 lx, 3000 K), it achieves a record-high PCE of 33.2%, demonstrating excellent indoor photovoltaic performance.
Why are carbon-based perovskite solar cells considered promising for commercialization?
Carbon-based perovskite solar cells are promising because they offer excellent operational stability and cost-effective fabrication processes, as they eliminate the need for expensive hole transport materials and metal electrodes.
What is the significance of the dual interfacial passivation strategy?
The dual interfacial passivation strategy simultaneously addresses defects at both the electron transport layer/perovskite interface and the perovskite top surface, effectively reducing nonradiative recombination and improving Voc, which is a critical step toward achieving efficiencies comparable to conventional devices.
Related Technical Papers & Translations
Direct Repair of the Crystal Structure and Coating Surface of Spent LiFePO4 Materials Enables Superfast Li-Ion Migration
The rapid accumulation of spent LiFePO4 (LFP) cathodes from retired lithium-ion batteries necessitates the development of effective and environmental-friendly recycling strategies. In this context, direct regeneration has emerged as a promising approach for reclaiming LFP cathode materials, offering a streamlined pathway to restore their electrochemical functionality. We report an integrated regeneration protocol that simultaneously repairs the degraded crystal structure and reconstructs the damaged carbon coating in spent LFP. The regenerated cathode material had superfast lithium-ion diffusion kinetics and a stable cathode–electrolyte interface, giving a remarkable rate capability with specific capacities of 122 mAh g−1 at 5C and 106 mAh g−1 at 10C (1C = 170 mA g−1). It also maintained capacities of 110.7 mAh g−1 (5C) and 84.1 mAh g−1 (10C) after 400 cycles. It could be used in harsh environments and could be stably cycled at subzero temperatures (−10 and −20 °C) and in solid-state electrolyte batteries. Life cycle assessment combined with economic evaluation using the EverBatt model reveals that this direct regeneration approach has high economic and environmental benefits.
Oxide Semiconductor for Advanced Memory Architectures: Atomic Layer Deposition, Key Requirement and Challenges
Oxide semiconductors (OSs), introduced by the Hosono group in the early 2000s, have evolved from display backplane materials to promising candidates for advanced memory and logic devices. The exceptionally low leakage current of OSs and compatibility with three-dimensional (3D) architectures have recently sparked renewed interest in their use in semiconductor applications. This review begins by exploring the unique material properties of OSs, which fundamentally originate from their distinct electronic band structure. Subsequently, we focus on atomic layer deposition (ALD), a core technique for growing excellent OS films, covering both basic and advanced processes compatible with 3D scaling. The basic surface reaction mechanisms—adsorption and reaction—and their roles in film growth are introduced. Furthermore, material design strategies, such as cation selection, crystallinity control, anion doping, and heterostructure engineering, are discussed. We also highlight challenges in memory applications, including contact resistance, hydrogen instability, and lack of p-type materials, and discuss the feasibility of ALD-grown OSs as potential solutions. Lastly, we provide an outlook on the role of ALD-grown OSs in memory technologies. This review bridges material fundamentals and device-level requirements, offering a comprehensive perspective on the potential of ALD-driven OSs for next-generation semiconductor memory devices.
Laser powder bed fusion of biodegradable Zn-4Cu alloy: Processing, microstructure and properties
Zn's natural degradability and biocompatibility make it a promising candidate for implants, however, its mechanical properties remain insufficient for bone applications. In this study, the performance of Zn was enhanced by developing Zn-Cu alloys via laser powder bed fusion (LPBF). Optimal LPBF parameters for forming stable tracks were achieved by adjusting laser power and scanning speed. Under optimized conditions of 100 W and 100 mm/s, high-density (99.58%) Zn-Cu alloys with improved hardness (68.2HV) and yield strength (160 MPa) were achieved. These improvements are attributed to solid solution strengthening, segregation strengthening, and grain refinement. The Zn-Cu alloys also demonstrated favorable degradation behavior, with a rate of 0.16 mm/year. This degradation is primarily driven by micro-galvanic corrosion between the CuZn5 phase and Zn matrix, along with refined grains and increased grain boundary density. This work demonstrates a viable strategy for fabricating Zn-based implants with enhanced structural integrity and mechanical performance via LPBF.