During holographic recording photopolymerizable materials experience spatially varying change of the refractive index due to change in molar refractivity and local density caused by illumination with spatially varying light intensity. Such materials found use in a wide variety of technologies, e.g. data transfer and storage, holographic solar concentrators, augmented and virtual reality displays. The key component of such materials is a photoinitiating system that triggers polymerization in the illuminated areas leading to the refractive index modulation and, as a result, formation of the diffraction grating. The holographic recording capability (sensitivity and dynamic range) of photopolymerizable materials depends on the photoinitiating system efficiency which is determined by its light absorption properties, initiating radicals quantum yield and radicals reactivity. These developments highlight the importance of the photoinitiating system choice to achieve the full technological potential of the holographic recording material in a specific application. In this work, holographic recording in cellulose acetate-PEG layers was employed to study the performance of novel diethoxycarbonyl-BODIPY -NPG photoinitiating system for free radical photopolymerization of acrylamide monomers under illumination with 532 nm light. Due to their high triplet state yields, BODIPY-pyrene and BODIPY-anthracene dyads 1b and 1d, respectively, were investigated. Although meso-9-methylanthracene dyad 1c showed even higher triplet state yield, it can undergo cycloaddition reaction with singlet oxygen similarly to previously reported BODIPY-anthracene dyads. Dyad 1d, which was used for photopolymerization instead, due to low reactivity of the anthracene group towards singlet oxygen as compared to 9-methylanthracene. 52 Performance of the novel dyes is compared with reference dyes, namely, meso-phenylBODIPY 1a and diiodoBODIPY (BDPI2). It is assumed that the binder polymer matrix (CA-PEG) is not reactive and is not involved in the photopolymerization process of acrylamide monomers that are evenly dispersed in the volume. CA-PEG layers containing monomers and photoinitiating system components have been prepared using a modified literature procedure, as described in detail in section 9.1 of the Supporting Information. The absorption spectra of the resulting materials showed characteristic BODIPY absorption bands at 503-534 nm (Figure ). For the recording, layers with 75-105 µm thickness were obtained through a drop-casting method followed by drying under a glass dish to slow solvent evaporation, as described in the ESI. This was in order to achieve clear, even layers across the substrate as it was observed that allowing rapid drying led to opaque, irregular layers. Dry layers showed low light scattering as seen from a clear image observed through the sample in Figure . This allowed for a reduction in losses due to scattering of light during holographic recording and achieving high diffraction efficiency of the grating. The polymerization of acrylamide and N,Nʹmethylenebisacrylamide in the CA-PEG materials under 532 nm excitation was confirmed by using Raman microspectroscopy, which has been previously used to study photopolymerization of these monomers. The reaction progress was monitored by changes in the characteristic vibrational peaks at 1600 cm -1 and 1623 cm -1 , which correspond to the C=C double bonds of acrylamide and methylenebisacrylamide, respectively. The spectrometer is equipped with both 785 nm and 532 nm lasers as options for Raman source (Figure ), and therefore the 532 nm laser was used as a polymerisation source and 785 nm as a Raman probe beam. During consumption of the monomers, the C=C double bond present in the monomer structure is converted into a C-C single bond leading to a decrease of the intensity of the associated Raman peak. Relative polymerization rates were compared by monitoring the decrease in the intensity of these two characteristic acrylamide Raman peaks as a function of 532 nm irradiation time. The peak area ratio was used in order to negate the effect of fluctuations in intensity due to background, scatter, and laser focus. The peaks at 1600 cm -1 and 1623 cm -1 were each fitted using a Gaussian-Lorentzian function, and the ratio of the peak areas was plotted versus time (Figure ). The experimental setup and results are shown in more detail in section 9.3 of the Supporting Information (Figures ). The results demonstrate that photopolymerization in these materials can be driven under 532 nm irradiation, and that both pyrene and anthracene dyads exhibited comparable photopolymerization rates relative to BDPI2 (Figure ). Figure represents the real-time diffraction efficiency growth curves of the transmission gratings with the spatial frequency of 800 lines/mm recorded in the layers containing pyrene and anthracene dyads, and reference photosensitizer BDPI2 as described in section 10 of the Supporting Information. Thickness of the gratings has been estimated from the Bragg selectivity curves (Figure ). Video in the supporting information demonstrates the performance of the transmission gratings recorded in CA-PEG layer sensitised with pyrene dyads under illumination with ambient light. The gratings selectively diffract light with different wavelengths of the spectrum at the specific angles (the Bragg angle). We attempted to perform holographic patterning of CA-PEG layer containing 1a and NPG. After exposure to the total recording intensity of 74 mW/cm 2 for 100 s, no diffracted intensity was detected, and no diffracted beam was observed. This indicates that 1a -NPG system has too low free radical generation capability to cause polymerization of acrylamide monomers. This can be explained by inefficient ISC in 1a which is manifested by low singlet oxygen generation quantum yields measured for this compound (Table ). The photosensitivity of the holographic recording material is directly linked to the polymerization rate, which depends on the ability of the photoinitiator to generate free radicals which lead to the formation of polymer chains and, as a result, the diffraction efficiency increase. The photosensitivity has been estimated from the linear part of growth curves (Supporting Information, section 10.3). As seen from Figure , the linear part of the curves for 1b and 1d have identical slopes, which denotes equal exposure sensitivity of the two compositions, and it is found to be 4 × 10 -4 mJ -1 cm 2 . The slope of the BDPI2 curve is lower and corresponds to the exposure sensitivity of 2 × 10 -4 mJ -1 cm 2 . The lower photosensitivity of layers containing BDPI2 can be explained by lower efficiency of the photoinitiating system containing BDPI2 and NPG to generate free radicals that initiate the formation of polymer chains. Thus, donor-acceptor dyads 1b and 1d have demonstrated a higher capability to initiate free radical