LED-based analysis of multijunction solar cells

LED’s MEASURE TANDEMS

Tandem Cells Demand High Accuracy

For tandem cells, I-V measurements that lack careful tuning of the spectrum or stabilization, result in significantly distorted I-V curves, short-circuit current (Isc), and fill factor (FF), which are not representative of real-world conditions. NREL’s survey of tandem cell measurement methodologies found that only a fifth of the published results are valid. LED’s up the game with reliable tandem measurements!

NREL study – Invalid perovskite publications

Poor solar simulator spectrum without adjustability can produce >10% error in short circuit current (Isc) (red), in contrast to a spectrum which has been adjusted properly (black). (1)

NREL analyzed perovskite-silicon tandem related publications. The spectrum was adjusted properly in less than 20% of the cases. Only a quarter of the cases used adequate (5 min) stabilization at MPP before reporting the maximum power. (1)

(1) Tao Song et al., How Should Researchers Measure Perovskite-Based Monolithic Multijunction Solar Cells’ Performance? A Calibration Lab’s Perspective, RRL (2022)

WAVELABS SOLUTIONS

Tandem EQE, Autocalibration, EL/PL & more

Working in collaboration with leading research institutes, WAVELABS has developed a comprehensive set of tandem measurement tools that allow fast, accurate, and thorough analysis of tandem solar cells.

Tandem EQE

EQE of the top and bottom subcell informs the subcell photocurrents and provides insight into the current limiting mechanisms and areas of improvement. WAVELABS’ automated EQE solution allows high throughput (500 ms), uses high quality illumination with A+ uniformity, and allows flexible bias voltage and bias illumination.

MPP-Tracking

EQE of the top and bottom subcell informs the subcell photocurrents and provides insight into the current limiting mechanisms and areas of improvement. WAVELABS’ automated EQE solution allows high throughput (500 ms), uses high quality illumination with A+ uniformity, and allows flexible bias voltage and bias illumination.

Autocalibration

Tandem Calibration is complex. Meeting the 60904-1-1 norm standards, the spectrum must be adjusted based on the tandem’s EQEs. With a smart algorithm, the perfect balanced spectrum is adjusted to calibration institute accuracy.

Calibration Kit

Accurate calibration requires precise measurement devices. This can be achieved with a versatile full-range spectrometer with high resolution, fully integrated into the software. The spectrometer can be easily integrated into the calibration chain.

Tandem EL/PL

Two cameras with replaceable filters can take pictures of the two sub-cells by either feeding current into the cell (EL) or illuminating the cell with narrow bandwidth LEDs (PL).