Atomic layer deposition of zinc oxide onto and into P3HT for hybrid photovoltaics

Abstract

ALD ZnO precursors diffuse into the disordered regions of a P3HT film yielding the bulk heterojunction morphology for hybrid photovoltaics.

Harnessing ALD to directly map the morphology of organic photovoltaic bulk heterojunctions

“…This phenomenon was used previously for processing hybrid organic/inorganic films for varying applications [3][4][5][6][7]. For example, we recently showed that the diffusion of diethyl zinc (DEZ) and water into P3HT films and the in-situ reaction leads to the deposition of ZnO nanocrystals inside the amorphous regions of P3HT [7]. This sub-surface deposition of ZnO was used to fabricate hybrid organic/inorganic photovoltaic films.…”

“…However, when applying metal-oxide ALD onto organic materials with no surface reactivity, the precursors diffuse into the organic film and generate a sub-surface deposition of the metal oxide. This phenomenon was used previously for processing hybrid organic/inorganic films for varying applications [3][4][5][6][7]. For example, we recently showed that the diffusion of diethyl zinc (DEZ) and water into P3HT films and the in-situ reaction leads to the deposition of ZnO nanocrystals inside the amorphous regions of P3HT [7].…”

“…After solvent outgassing the films were exposed to an ALD sequence of 60 1 torr /1 s DEZ/water cycles at 60°C. These deposition conditions were chosen according to our previous report [7] to ensure precursor penetration throughout the organic films while avoiding extensive ZnO mass accumulation which leads to film swelling. Under such conditions, we can probe the BHJ morphology without significantly altering it.…”

“…3 shows the integrative Zn mass incorporated in the organic layers as a function of PCBM concentration. The Zn mass accumulation was calculated from EDS measurements [7] and then normalized to its amount in the P3HT film that had no PCBM at all. Fig.…”

Hydrothermally grown ZnO electrodes for improved organic photovoltaic devices

“…While strategies to prepare hybrid photovoltaics i.e. where the oxide acts as both an active material and the electron transport layer have had limited success [19][20][21][22] the incorporation of a nanostructured electron acceptor here, using simple device structures processed in ambient, is shown to improve performance. Unlike previous reports where multistep patterning was required or where non-standard conjugated materials utilized [23] here we describe the preparation of bulk heterojunction photovoltaic devices using the commonly used, widely available active materials poly(3-hexylthiophene-2,5-diyl) (P3HT) -indene-C 60 bisadduct (IC 60 BA) using planar and nanostructured ZnO electron extracting layers and report on the device improvements enabled by incorporating nanorod electrodes and the impact these electrodes have on the optimum active layer composition.…”