The stability of regioregular poly(3-hexylthiophene 2,5-diyl) (P3HT) thin films sandwiched between indium tin oxide (ITO) and aluminium (Al) electrodes have been investigated under normal environmental conditions ($25^{\circ}$C and RH$\sim 45-50$%). Electrical and optical properties of ITO/P3HT/Al devices have been studied over a period of 30 days. Mobility 𝜇 of the order of $10^{-4}$ cm²/V-s has been obtained from the $V^{2}$ law in the as- deposited P3HT ¯lms. Scanning electron microscopy (SEM) investigations show blistering of Al contacts in devices with a poly(3,4-ethylenedioxythiophene) (PEDOT) interlayer on application of voltage whereas no blistering is seen in devices without PEDOT. The results have been explained in terms of trap generation and propagation and the moisture-absorbing nature of PEDOT.