Perovskite solar cells (PSCs), with a technological breakthrough exceeding 27% power conversion efficiency within two decades, have become the core direction for the industrialization upgrade of the photovoltaic industry. Photoluminescence (PL) and electroluminescence (EL) inspection technologies, as essential means for characterizing the intrinsic properties of perovskite materials, device defects, and optoelectronic performance, have evolved from basic laboratory research tools into key quality control technologies spanning the entire lifecycle of perovskite cell R&D, pilot production, and mass manufacturing. In recent years, technological innovations in in-situ, high-resolution, intelligent, and multi-modal fusion have propelled PL/EL inspection from "defect identification" to "mechanism tracing" and then to "process closed-loop optimization," providing critical support for efficiency enhancement and stability breakthroughs in perovskite cells. This article, integrating the latest technological research and industrial application achievements, reviews the technological frontiers and development trends of PL/EL inspection for perovskite solar cells.

I. Core Principles and Technological Value of PL/EL Inspection

1. Photoluminescence (PL) Inspection: A "Microscopic Probe" for Intrinsic Material Properties

PL inspection uses lasers or LEDs at specific wavelengths (e.g., 405nm, 532nm) to excite perovskite materials, causing electrons to transition from the valence band to the conduction band, forming electron-hole pairs. By analyzing parameters such as fluorescence spectrum intensity, peak position, full width at half maximum, and lifetime resulting from radiative recombination, it precisely characterizes material crystallization quality, defect state density, carrier transport efficiency, and phase purity. Time-resolved PL (TRPL) technology, using femtosecond/picosecond pulse excitation and time-correlated single photon counting (TCSPC) systems, can distinguish the contributions of surface recombination and bulk recombination, providing quantitative basis for defect passivation and interface engineering design. Research by the team of Cheng Yuanhang at Nanjing University of Science and Technology in 2026 confirmed that PL technology enables real-time tracking of perovskite nucleation, crystal growth, phase transitions, and defect evolution, serving as a bridge connecting crystallization mechanism research and device process control.

2. Electroluminescence (EL) Inspection: A "Performance X-ray Vision" for Device Operating Status

EL inspection applies a forward bias to perovskite cells, exciting internal electron radiative recombination. By analyzing luminescence intensity, spectral distribution, and spatial imaging, it reveals process defects such as cracks, poor soldering, and phase separation, while quantifying non-radiative recombination activity and trap state density under operating conditions. Unlike PL's material characterization, EL inspection is closer to the actual working scenario of the cell, directly reflecting the full-chain performance of charge injection, transport, and collection. It is a core means for screening device failures in mass production. Low-temperature EL spectroscopy studies have also found that the heterogeneity in optoelectronic performance of perovskite cells below 240K is directly related to local charge injection bottlenecks, providing a characterization basis for the application of perovskite cells in special scenarios like space power.

3. PL/EL Fusion: A Technical Closed Loop for Full-Dimension Performance Characterization

PL inspection focuses on intrinsic material properties, while EL inspection focuses on device process defects. Their integration achieves full-dimension performance characterization from "material-interface-device." By using PL to analyze the crystallization uniformity and defect distribution of perovskite films, combined with EL to verify the rationality of device preparation processes, a closed-loop analysis system of "material optimization - process adjustment - performance verification" is formed. Defect recognition accuracy can be increased to 99%, and the missed detection rate reduced to below 1%, laying the foundation for high-quality mass production of perovskite cells.

II. Cutting-Edge Breakthroughs in Perovskite PL/EL Inspection Technology

In recent years, PL/EL inspection technology has achieved core breakthroughs in four major directions: high resolution, in-situ capabilities, intelligence, and tandem cell adaptation. These breakthroughs have solved the technical bottlenecks of traditional characterization methods, which struggled to analyze microscopic non-uniformity and track dynamic processes, pushing inspection capabilities from "macro-qualitative" to "micro-quantitative."

1. Submicron High-Resolution Imaging: Enabling Precise Defect Localization and Mechanism Tracing

The breakthrough in Quasi-Fermi level splitting (QFLS) imaging technology has increased the spatial resolution of PL inspection to 260nm, directly reflecting the spatial distribution of electron-hole quasi-Fermi level splitting within the device. It has become a core means for evaluating intrinsic open-circuit voltage (Voc) potential and voltage losses. The PC100 characterization system launched by Chuangrui Spectrum in 2025 combines laser confocal scanning with wide-field imaging, enabling the localization of Voc loss regions caused by material defects and grain boundaries at the submicron scale, while also achieving spatial imaging of photoluminescence quantum efficiency (PLQE) and carrier lifetime. This provides in-situ quantitative feedback for optimizing the uniformity of thin-film deposition processes. EL inspection, through glass-side imaging to avoid electrode shading and combined with high-resolution spectral mapping, enables visualization of phase separation and compositional fluctuations, solving the technical challenge of characterizing phase purity in mixed-halide perovskites.

2. In-Situ PL Inspection: Dynamically Tracking the Entire Perovskite Crystallization Process

Traditional characterization methods like XRD and SEM can only capture the static structure of perovskite films. In contrast, in-situ PL inspection, as a non-invasive technique, can track the entire process of perovskite nucleation, crystal growth, phase transitions, and defect evolution in real-time under moderate laser illumination. A 2026 review by Cheng Yuanhang's team in Advanced Materials pointed out that in-situ PL technology can clearly reveal the influence of anti-solvents, additives, and interface engineering on the formation process of perovskite films, providing precise guidance for process optimization. Through upgrades in Y-shaped fiber integration systems, dynamic scanning PL, and multi-channel imaging technologies, the signal-to-noise ratio and spatial resolution of in-situ PL inspection have been significantly improved, effectively avoiding spectral distortion caused by re-absorption and scattering. This enables precise analysis of crystallization kinetics in mixed-halide systems.

3. AI Intelligence and Automation: Achieving Intelligent Defect Recognition and Process Linkage

The deep integration of AI algorithms with PL/EL inspection is pushing the technology from "data acquisition" to "intelligent analysis." The PL/EL all-in-one inspection system launched by Wuhan Aijia Technology features self-developed AI algorithms that automatically identify defect types, generate repair suggestions, and seamlessly connect with production lines for automatic loading/unloading and testing, reducing errors from manual intervention. Intelligent data management systems enable real-time storage, query, and traceability of inspection data, providing data support for production quality control. Additionally, AI algorithms can rapidly fit and analyze PL/EL spectral data, automatically calculating key parameters such as trap state density and carrier lifetime, improving inspection efficiency by more than five times.

4. Dedicated Inspection for Tandem Cells: Achieving Decoupled Analysis of Sub-Cell Performance

Perovskite/silicon tandem cells are a core direction for exceeding 30% power conversion efficiency, but the coupling of sub-cell performance poses a bottleneck for characterization techniques. To address this challenge, the latest PL/EL inspection technology introduces a multi-wavelength excitation tomography scheme. Using 450nm laser to selectively excite the perovskite top cell and 850nm laser to excite the silicon bottom cell, it can independently acquire PL/EL intensity imaging, QFLS imaging, and pseudo J-V curve imaging for each sub-cell, precisely analyzing the Voc, Jsc, defect distribution, and power conversion efficiency of individual sub-cells. This technology achieves decoupled analysis of tandem cell performance, providing a key means to overcome current matching and energy level alignment challenges, accelerating the R&D process for tandem cells.

III. Industrial Application and Implementation of PL/EL Inspection Technology

As perovskite cells transition from laboratory R&D to industrial mass production, PL/EL inspection technology now covers the full spectrum of scenarios: scientific R&D, pilot optimization, mass production quality control, and power plant O&M, establishing itself as the "quality gatekeeper" for the perovskite photovoltaic industry.

1. Scientific R&D: Accelerating Technology Iteration for Materials and Devices

During the laboratory R&D phase, PL/EL inspection technology provides quantitative basis for optimizing new perovskite materials and device structures. Using PL inspection to screen perovskite film formulations with high crystallization quality and low defect density, combined with EL inspection to verify the effectiveness of interface engineering and passivation treatments, can significantly shorten the R&D cycle for new materials. Research-grade characterization systems like the PC100 integrate full-dimensional functions such as PL, EL, TRPL, and photocurrent imaging, enabling correlation analysis of "process parameters - microstructure - optoelectronic performance," providing powerful technical support for efficiency improvements in perovskite cells.

2. Mass Production Quality Control: Building a Zero-Defect Manufacturing System

In mass production, PL/EL inspection technology becomes a core component of quality control for perovskite cells and modules. Industrial inspection equipment launched by companies like Nanjing Vision Potential and Wuhan Yaohua Laser enables comprehensive screening of modules before and after lamination, precisely capturing process defects such as micro-cracks, broken grids, and poor soldering, while also being compatible with mainstream cell technologies like PERC and TOPCon. Vision Potential's perovskite-specific inspection equipment is equipped with an AM1.5G standard spectrum light source and high transient pulse light source, allowing rapid inspection processes while avoiding light-induced degradation interference. It supports a wide range of electrical parameter tests (±20V/±2A), precisely capturing core cell performance indicators, and adapts to the efficient inspection needs of various production line scales.

3. Full Lifecycle Monitoring: Supporting Reliability Improvement of Perovskite Cells

PL/EL inspection technology can also be applied to aging tests and power plant O&M for perovskite cells. By tracking PL peak shifts and EL intensity attenuation under different aging conditions, it reveals the degradation mechanisms of perovskite films (e.g., ion migration, phase separation). Portable PL/EL inspection equipment enables on-site inspection of photovoltaic power plants, accurately assessing module degradation, providing data support for efficient plant O&M. Through full lifecycle PL/EL inspection, a performance degradation database for perovskite cells can be established, offering directions for optimizing the long-term stability of devices.

IV. Technology Development Trends and Challenges

1. Core Development Trends

In the future, perovskite PL/EL inspection technology will develop towards higher resolution, faster inspection, full-process integration, and multi-technique combination. On one hand, nanoscale-resolution PL/EL imaging will enable performance characterization of single perovskite crystals, providing more precise tools for microscopic mechanism research. On the other hand, breakthroughs in high-speed inspection technology will enable real-time online inspection in mass production, with inspection speeds matching the flow requirements of production lines. Simultaneously, PL/EL inspection will deeply integrate with techniques like in-situ XRD, SEM, and impedance spectroscopy, forming a multi-dimensional, multi-scale characterization system for comprehensive analysis of perovskite cell optoelectronic performance. Furthermore, the miniaturization and portability of inspection equipment will promote its widespread application in scenarios like photovoltaic power plant O&M and outdoor testing.

2. Existing Technical Challenges

Despite significant breakthroughs, PL/EL inspection technology still faces three core challenges: First, the photosensitivity of perovskite materials can easily lead to photodamage during inspection, affecting data accuracy. Second, the non-uniformity of large-area perovskite films causes statistical bias in inspection data, requiring more efficient area scanning techniques. Third, the structural complexity of novel devices like tandem cells and flexible perovskite cells imposes higher requirements on the specificity and adaptability of inspection techniques. Additionally, standardization of inspection technology is crucial for industrial implementation. Currently, there is no unified PL/EL inspection standard, leading to a lack of comparability in inspection data from different equipment, urgently requiring industry collaboration to establish a standard system.

V. Conclusion

PL/EL inspection technology, as a core characterization method for the R&D and industrialization of perovskite solar cells, has achieved comprehensive breakthroughs from basic research to industrial applications, becoming a key support for improving efficiency, enhancing stability, and enabling mass production of perovskite photovoltaic technology. Technological innovations in in-situ capabilities, high resolution, intelligence, and multi-modal fusion enable PL/EL inspection not only to precisely identify defects but also to deeply analyze the intrinsic mechanisms of optoelectronic performance, providing quantitative basis for process optimization of perovskite cells. With the continuous upgrading of inspection technology and the establishment of standardization systems, PL/EL inspection will play an even more important role in the high-quality development of the perovskite photovoltaic industry, helping perovskite cells make the leap from laboratory to market and becoming one of the core competitive strengths of the future photovoltaic industry.

The portable daylight EL tester SC-DEL-Portable, developed by Vision Potential's R&D team, uses an InGaAs sensor combined with patented filtering and phase-locking principles to perform EL testing 24 hours a day. It is one of the few known devices on the market capable of all-day EL testing.