The kinetics of diffusion-controlled triplet-triplet annihilation (TTA) and simultaneous delayed fluorescence (DF) of meso-tetraphenylporphyrin (TPP) in thin films (1-100 run) of n-decanol (DEC) adsorbed on the external surface of NaA zeolite were studied by the diffuse-reflectance laser flash technique in the temperature range 220-330 K. The value of the TTA bimolecular rate constant (k(TTA)(L)) referred to the DEC volume in the solid samples (with the amount of DEC being greater than or equal to 10 monolayers) is similar to that measured in neat DEC. At temperatures above the melting point of DEC (280 K), the decrease of the DEC film thickness to one monolayer results in 20-fold increase of k(TTA)L which is attributed to the confined reaction volume where TPP is concentrated as well as to the enhanced TPP diffusion in this volume. The DEC monolayers on the NaA external surface are vertically ordered DEC molecules with external hydrocarbon region characterized by enhanced molecular mobility confirmed by solid-state H-1 NMR spectra. The apparent rate of TTA in neat DEC or in bulk DEC multilayers increases by more than I order of magnitude with the freezing of DEC and further temperature decrease down to 260 K whereas that in DEC monolayers does not. The apparent k(TTA)(L) value measured far below the melting point of DEC is independent of DEC film thickness and coincides with that in neat frozen DEC which presents some organized monolayers with TPP localized in the vicinity of aliphatic chains.