A modular system for angle-resolved spectroscopy of OLEDs

Angle-resolved photoluminescence (PL) and electroluminescence (EL) measurements reveal optical information in organic light-emitting diodes (OLEDs) that remains hidden in conventional single-angle measurements — and are therefore important for understanding and optimizing device performance. However, the broader adoption of these techniques is hindered by the cost and limited adaptability of commercial instrumentation. Moreover, the rapid degradation of many organic emissive materials creates a need for fast measurements under controlled environmental conditions. Here, we present a modular and accessible system for angle-resolved PL and EL characterization of light-emitting devices. The system provides a 180° angular range with a sub-degree resolution, rapid setup and sequential data acquisition, and flexibility in the selection of optical and electrical components. A dedicated sample holder enables electrical injection while maintaining unencapsulated samples under vacuum. This allows degradation-sensitive devices to be measured without exposure to ambient conditions, eliminating the need for the time-consuming and irreversible encapsulation normally required for ex situ characterization. We provide detailed procedures for assembling, calibrating the system, conducting angle-resolved measurements, and processing the resulting data. The performance of the system is demonstrated using OLEDs based on a well-established thermally activated delayed fluorescence (TADF) emitter. This adaptable platform lowers the practical barriers to advanced optical characterization and provides a versatile tool for OLED and organic-laser research.