Pure and copper doped cellulose microfibers-a case study

Our work demonstrates the improvement of intrinsic properties of cellulose microfibers upon copper doping. Cellulose microfibers were extracted from cotton by hydrolysis process. These were further doped with copper (Cu) to see the effect of dopant on optical, structural and conducting properties. We investigated the potential usage of these microfibers to solar cell applications. The evolution of cellulose microfibers has been comprehensively investigated with increasing dopant concentration of Cu (5 to 15%). Scanning electron microscopy gives clear images of cellulose microfibers of average diameter 5–10 μm. Absorption spectra of all samples showed an onset of absorption between 5.07 to 3.93 eV. A red shift was observed in band gap upon doping which is indicative that Cu has been incorporated into cellulose. DC conductivity studies reveal an improvement in conductivity values after Cu doping (303 to 363 K) from 8.89 × 10−5 to 5.04 × 10−4 S cm−1. These fibers were then coated over a Si solar cell and found an increase in short circuit current from 66 to 100 mA. The increase in short circuit current is attributed to charge transfer because of Cu metal and further reduces electron hole recombination which in turn improved the overall efficiency.