Organic inorganic hybrid solar cell with photoactive hole transporting CuSbS2 nanoflakes

Abstract

An easy-to-process, low-cost and environmentally benign organic inorganic hybrid solar cell (HSC) based on textured silicon (t-Si) is fabricated. The heterojunction solid state cell is composed of n-type t-Si having a micro-pyramidal surface with good anti-reflection properties, coated with a p-type layer of CuSbS2 nanoflakes dispersed in a polymer matrix of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The large hole density (2.7 × 1015 /cm3), high photoconductivity (5.37 mS cm−1), mono-dispersity of nanoflakes (50–80 nm), increased recombination resistance and a broad band absorption, with a band gap of ∼ 0.85 eV render CuSbS2 nanoflakes to be an ideal photo-absorber cum hole transport material for a highly scalable all solid-state HSC. Besides these attributes, the thermodynamically aligned energy levels of t-Si and CuSbS2 nanoflakes enable one-directional pathways for transfer and transport of electrons and holes to their respective contacts, yielding a high-power conversion efficiency (PCE) of 8.5 % under AM 1.5, 1 sun irradiance along with an average external quantum efficiency of 60 % superior by 39.2 % relative to its analogue devoid of CuSbS2. The effect of alkali texturization on the photovoltaic performance of the cells is also delineated by comparison with planar (pl)-Si based cells. The long-term stability of the In-Ga/t-Si/PEDOT:PSS + CuSbS2/Ag cell under intermittent illumination and storage over eight weeks confirmed from the nominal drop in PCE by ∼ 22 % demonstrates the efficacy of this affordable wet-chemistry approach for developing robust Si based HSC contrasting with the classical and expensive inorganic p-n junction crystalline Si solar cell.