Unravelling the mechanisms of emission enhancement in quantum emitters coupled to one-dimensional photonic crystals

Quantifying light–matter interactions is crucial for the design of nanophotonic devices, but remains challenging because excitation, recombination, photon extraction, and collection processes are strongly intertwined. Here, we developed a quantitative framework to decouple these processes by combining angle-resolved photoluminescence (PL), direct PL quantum yield (PLQY), PL lifetime measurements, and full-wave simulations. Our study focuses on large-area one-dimensional photonic crystals (PC) coupled with a thin film of CsPbI3 perovskite nanocrystals (NCs). By intentionally minimizing excitation enhancement through careful system design ( $${\eta}_{exc}=1$$ and $${\eta}_{exc}=1.15$$ for S- and P-polarizations, respectively), we assess emission-side processes as the dominant contributors to the experimentally observed PL enhancement. The system yields a 110‑fold in PL enhancement mediated by quasi-bound states in the continuum (quasi-BIC) while a tenfold enhancement is achieved via normal Bloch resonances, relative to the PL intensity on glass. Our quantitative decomposition reveals that the quasi-BIC enhancement is primarily driven by photon extraction (factor ~21), far exceeding contributions from QY enhancement (factor of 1.94), and collection efficiency (factor of 3.25). In contrast, the enhancement associated with the Bloch resonances (~ tenfold) arise from a more balanced interplay of extraction (factor of 2.71), QY enhancement (1.37) included Purcell-based emission rate enhancement (factor of 1.24), and improved collection efficiency (factor of 3.2). These findings uncover the interplay of concurrent processes and provide a quantitative validation of the reciprocal principle for designing resonant light-emitting surfaces. Our work establishes a broadly applicable framework for evaluating exciton-cavity interactions in lossy systems, enabling precise control of light emission for high-efficiency optoelectronic devices, quantum light sources, and advanced sensing technologies.