Perovskite cell EL/PL tester: the key eye of lighting efficiency and defects

　　Accurately characterizing the optoelectronic performance and internal defect status of perovskite solar cells (PSCs) is crucial on the rapidly developing path. The perovskite cell EL/PL tester is the core diagnostic tool designed for this purpose, like installing a "perspective eye" and "stethoscope" on the battery, providing indispensable support for understanding the working mechanism of the device, improving conversion efficiency and long-term stability.

　　The perovskite cell EL/PL tester integrates two powerful non-destructive detection technologies, electroluminescence (EL) and photoluminescence (PL), to meet the demand for multidimensional and high-sensitivity analysis of perovskite cells.

　　Revealing Carrier Behavior and Defects: The Power of Electroluminescence (EL) Testing

　　When a forward bias is injected into perovskite solar cells, the injected electrons and holes recombine within the perovskite layer, releasing some of the energy in the form of photons, resulting in electroluminescence. The EL imaging function in the perovskite cell EL/PL tester can capture the infrared or near-infrared light signals emitted by the entire working area of the battery and convert them into a visual distribution map of luminescence intensity.

　　Uniformity evaluation: The luminescence image directly reflects the carrier recombination efficiency in different regions of the battery. A region with uniform luminescence usually means high material quality, good film coverage, and excellent interface contact. On the contrary, dark spots or uneven brightness clearly indicate possible issues such as pinholes, grain boundary defects, compositional segregation, or poor local contact. The perovskite cell EL/PL tester is a powerful tool for evaluating the consistency of large-area perovskite cell preparation processes.

　　The correlation between series resistance and efficiency: The EL intensity is closely related to the degree of quasi Fermi level splitting of the battery under a specific bias voltage, theoretically proportional to the open circuit voltage (Voc). Therefore, by analyzing the distribution of EL intensity and its relationship with bias voltage, the EL/PL tester for perovskite cells can indirectly reflect the distribution of series resistance inside the cell, providing clues for optimizing electrode design and interface engineering.

　　Potential failure point localization: Abnormal dark areas or cracks appearing on EL images after battery operation or aging are often the starting points of performance degradation or ultimate failure. The use of perovskite cell EL/PL tester for in-situ monitoring of EL is an effective means to study the degradation mechanism of batteries and predict their lifespan.

　　Insight into the intrinsic properties of materials: in-depth analysis of photoluminescence (PL) testing

　　Unlike EL, photoluminescence (PL) testing uses lasers or other light sources with specific wavelengths (usually above the absorption edge of perovskite materials) to excite perovskite cell samples. The excited electrons jump to high energy levels and then fall back to the valence band to recombine with holes, emitting fluorescence of a specific wavelength. The EL/PL tester for perovskite cells is equipped with high-sensitivity detectors (such as CCD, InGaAs array) and high-resolution spectrometers that can accurately collect PL signals.

　　Material quality and defect density of states: The PL intensity of perovskite thin films is a sensitive probe for their non radiative recombination losses (mainly caused by defects). High PL intensity usually means good crystalline quality and low defect density of the thin film. By measuring the carrier lifetime through time-resolved photoluminescence (TRPL), the EL/PL tester for perovskite cells can quantitatively evaluate the effect of different processes or passivation strategies on reducing non radiative recombination centers.

　　Band structure and composition analysis: The PL peak position of perovskite materials directly reflects their bandgap size. By using a perovskite cell EL/PL tester for PL mapping (surface scanning), the bandgap distribution at different positions on the thin film or cell can be visually displayed, effectively identifying bandgap fluctuations caused by uneven composition or phase separation. This is particularly crucial for precise bandgap control in pursuit of high-efficiency stacked cells.

　　Interface and Carrier Transport Dynamics: Comparing the PL quenching degree and rate of individual perovskite thin films with complete devices (including transport layers), the perovskite cell EL/PL tester can evaluate the efficiency of electron transport layer (ETL) or hole transport layer (HTL) in extracting carriers, revealing potential energy loss or recombination issues at the interface.

　　Testing equipment optimized specifically for perovskite properties

　　An efficient and accurate perovskite cell EL/PL tester needs to meet the special requirements of perovskite materials:

　　High sensitivity and wide spectral response: The EL/PL signal of perovskite is usually weak and located in the near-infrared band (mainly around 750-850nm), requiring instrument detectors to have extremely high quantum efficiency and low noise characteristics, covering the visible near-infrared spectral range.

　　High spatial resolution: In order to capture defects at the micrometer or even sub micrometer scale (such as grain boundaries and small pinholes), imaging systems need to have excellent optical resolution.

　　Precision environmental control (optional): Considering the sensitivity of perovskite materials to water and oxygen, some high-end perovskite cell EL/PL testers integrate glove box or environmental chamber interfaces, supporting in-situ and long-term stability monitoring under inert atmosphere.

　　Multi functional integration and automation: Combining current voltage (I-V) testing, quantum efficiency (QE) measurement modules, and possessing automated sample stages and software analysis capabilities (such as automatic identification of dark spots, calculation of uniformity, and fitting of PL lifetime), is the key to improving research and production line efficiency for modern perovskite cell EL/PL testers.

　　With the advancement of perovskite photovoltaic technology towards higher efficiency, larger area, and longer lifespan, a deeper understanding and precise control of the internal physical and chemical processes of devices have become unprecedentedly important. The perovskite cell EL/PL tester has become a core equipment that runs through the entire chain of basic material research, device process optimization, mass production quality control, and failure analysis, thanks to its non-destructive, high spatial resolution, and quantitative analysis advantages. It is not only the "eye" that reveals the secrets inside perovskite cells, but also the solid cornerstone that drives this disruptive technology towards maturity and industrialization. Continuously improving the detection accuracy, flux, and intelligence level of perovskite cell EL/PL testers will be a key link supporting the future development of perovskite photovoltaics.