Previously, we reported the synthesis and application of transparent conductive polymer (TCP) films, poly(arylene ether ketone) copolymers (co-PAEKs), for forming direct contact between wires and transparent conductive oxide (TCO) layers in silicon solar cells. The polymers have the lowest peak strain temperature (T-d), which determines the contact formation temperature, of 205 degrees C. To utilize such TCP films in silicon heterojunction (SHJ) solar cells with amorphous silicon layers, T-d should be lowered. To solve the problem in question, a number of co-PAEKs with a decreased reduced viscosity (eta(red)) due to a decreased molecular weight of the polymer have been synthesized in this study. It has been shown that lowering eta(red) from 0.56 to 0.4 dl/g markedly improves the main properties of the co-PAEKs. In particular, (i) T-d decreased from 205 to 189 degrees C, (ii) the peel strength, determined by pulling off the wires from the polymer surface, increased from 1.69 +/- 0.26 to 3.55 +/- 0.84 N/mm, and (iii) the resistivity of the wire/TCP/ITO (In2O3:Sn) contact, rho(C), dropped from 1.20 to 0.67 m Omega cm(2). At the same time, the optical properties of the copolymers remained unchanged. We have fabricated bifacial rear junction SHJ solar cells based on a ITO/(n)alpha-Si:H/(i)alpha-Si:H/(n)Cz-Si/(i)alpha-Si:H/(p)alpha-Si:H/ITO structure, with wire contact grids attached to the ITO layers using co-PAEK films. A solar cell produced using the co-PAEK film with the lowest reduced viscosity had an efficiency under front/rear illumination of 19.6%/18.4%. At 1-sun front illumination and 20/50% of 1-sun rear illumination, the equivalent efficiency is equal to 23.3%/28.8%.