Traditionally, two different techniques have been used to enhance the spectral operating range of a photodetector, i.e., either combining materials of different bandgaps or combining semiconductor materials to form tertiary alloys. However, these methods involve multiple synthesis/processing steps and complex clean room-based fabrication. Addressing this, a simple and novel step in device architecture is demonstrated by surface engineering of Cu buffer layer in between a paper substrate and Cu2S to develop a highly responsive photodetector with tunable operating range. Cu2S nanoparticles were grown directly on the surface of Cu pre-deposited paper substrate using facile hydrothermal technique to obtain Ag/Cu2S/Ag - metal semiconductor metal (MSM) configuration on Cu/paper substrate. The morphological characterization revealed the uniform distribution of Cu2S nanoparticles on the surface of cellulose microfibers and the structural studies confirmed the formation of highly crystalline cubic - Cu2S with Cu-S stretching vibrations. In comparison to the pristine Ag/Cu2S/Ag on paper photodetector, the buffer-based Ag/Cu/Cu2S/Ag photodetector displayed excellent response from visible to NIR region. A superior responsivity and detectivity of 27 mA/W and 2.5 ×108 Jones respectively are observed for Cu buffer/Cu2S photodetector. The obtained response of the paper/Cu/Cu2S device can be attributed to the synergistic combination of Cu buffer layer induced reduction of defect sites and LSPR induced transfer of electrons from the Cu metal to Cu2S. The paper-based photodetector displayed a fast response time of 0.09 sec, and excellent mechanical stability and durability for 1000 bending cycles. The surface engineering of a buffer layer in the photodetector architecture certainly bridges a technological gap and presents a new strategy for development of high-performance optoelectronic devices. © 2022 Elsevier B.V.