SPLTRAK Abstract Submission
Polyethienimine interface dipole tuning for electron selective contacts
Eloi Ros1, Thomas Tom2, Gerard Masmitja1, benjamin pusay1, estefania almache1, Julia Lopez2, maykel jimenez1, pablo ortega1, edgardo saucedo1, Joan Bertomeu2, joaquim puigdollers1, Cristobal Voz1
1Universitat Politécnica de Catalunya, Barcelona, Spain
/2Universitat de Barcelona, Barcelona, Spain

Abstract: This work studies the use of thin layers of polyethylenimine (PEI) as an interface film to produce electron selective contacts for photovoltaic applications in crystalline silicon. Generally, in conjugated polyelectrolytes such as PEI with a high Lewis basicity, charge is accumulated along the chain of the polymer and counter anions from the solvent create an intense dipole array. In this work, part of the amine groups in PEI are protonated by the solvent that behaves as a weak Brønsted acid during the process. The PEI band modification is able to eliminate Fermi level pinning at metal/semiconductor junctions as it shifts the work function of the metallic electrode by more than 1 eV. As a consequence, induced charge transport between the metal and the semiconductor forms an electron accumulation region and promotes enhanced selectivity.