Effect of substrate bias on mist deposition of conjugated polymer on textured crystalline‐Si for efficient c‐Si/organic heterojunction solar cells

Abstract

We investigated the chemical mist deposition (CMD) of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on textured crystalline silicon (c‐Si) substrate for efficient c‐Si/PEDOT:PSS heterojunction solar cells. The Mie scattering observation and differential mobility analysis characterization revealed that the average size of mist particle decreased from 330 to 30–40 nm with increasing the number density and traveling velocity of mist precursor when positive dc bias of 10 kV was applied to the c‐Si substrate. The uniform deposition of PEDOT:PSS films was performed on textured c‐Si with the increased adhesion by suitably adjusting Vs and substrate temperature. A power conversion efficiency (PCE) of 11.57% was obtained with Jsc of 36.1 mA cm−2, Voc of 0.49 V, and FF of 0.66, when a positive Vs of 10 kV was applied to c‐Si substrate. Furthermore, PCE increased to 12.5% with Jsc of 35.6 mA cm−2, Voc of 0.53 V, and FF of 0.67 by adding a 20‐nm‐thick AR coating layer of molybdenum oxide MoOx (refractive index, n = 2.1) fabricated by CMD using 12 molybdo(VI) phosphoric acid n‐hydrate [H3(PMo12O40) · nH2O] as a precursor. These findings imply that CMD using negatively charged mist precursor is a possible method for the uniform deposition of PEDOT:PSS on textured c‐Si substrate for efficient c‐Si/PEDOT:PSS heterojunction solar cells.