Toward High‐Efficiency Solution‐Processed Planar Heterojunction Sb₂S₃ Solar Cells

Abstract

Low‐cost hybrid solar cells have made tremendous steps forward during the past decade owing to the implementation of extremely thin inorganic coatings as absorber layers, typically in combination with organic hole transporters. Using only extremely thin films of these absorbers reduces the requirement of single crystalline high‐quality materials and paves the way for low‐cost solution processing compatible with roll‐to‐roll fabrication processes. To date, the most efficient absorber material, except for the recently introduced organic–inorganic lead halide perovskites, has been Sb2S3, which can be implemented in hybrid photovoltaics using a simple chemical bath deposition. Current high‐efficiency Sb2S3 devices utilize absorber coatings on nanostructured TiO2 electrodes in combination with polymeric hole transporters. This geometry has so far been the state of the art, even though flat junction devices would be conceptually simpler with the additional potential of higher open circuit voltages due to reduced charge carrier recombination. Besides, the role of the hole transporter is not completely clarified yet. In particular, additional photocurrent contribution from the polymers has not been directly shown, which points toward detrimental parasitic light absorption in the polymers. This study presents a fine‐tuned chemical bath deposition method that allows fabricating solution‐processed low‐cost flat junction Sb2S3 solar cells with the highest open circuit voltage reported so far for chemical bath devices and efficiencies exceeding 4%. Characterization of back‐illuminated solar cells in combination with transfer matrix‐based simulations further allows to address the issue of absorption losses in the hole transport material and outline a pathway toward more efficient future devices.

Enhanced Electrical Conductivity of Sb2S3 Thin Film via C60 Modification and Improvement in Solar Cell Efficiency

“…The photocurrent of the bare Sb 2 S 3 sample was around 40 µA, while that of the C 60 ‐modified Sb 2 S 3 sample was higher than 70 µA under light condition. This result suggested that both the transverse and longitudinal photoconductivity of the Sb 2 S 3 thin films could be improved by C 60 modification …”

“…This result suggested that both the transverse and longitudinal photoconductivity of the Sb 2 S 3 thin films could be improved by C 60 modification. [26,27] The photovoltaic characteristics of the solar cells, in superstrate configuration, with bare Sb 2 S 3 and C 60 -modified Sb 2 S 3 absorber layers, respectively, were measured under AM 1.5G illumination. The J-V curves of the devices are shown in Figure 3a.…”

Spin-coated planar Sb2S3 hybrid solar cells approaching 5% efficiency

“…Solar cells with extremely thin absorber architecture [1–6 29] reach the highest efficiencies. Planar devices have been produced via various methods such as atomic layer deposition (ALD) [32], chemical bath deposition (CBD) [27] and (rapid) thermal evaporation (R)TE [33–35]. As the latest development, spin-coated planar solar cells [31,36–38] reached an efficiencies >4%.…”

Microstructural and Optical Properties of Sb2S3 Film Thermally Evaporated from Antimony Pentasulfide and Efficient Planar Solar Cells

“…At the same time, aqueous chemical bath depositions (CBD) have been commonly employed with a solution mixture of antimony chloride and sodium thiosulfate as a precursor source of Sb 3þ and S 2À ions at low temperature for the deposition of Sb 2 S 3 , respectively. [4,[18][19][20] By this method Ma et al [18] received a PCE of 3.52% with a device configuration of ITO/TiO 2 /Sb 2 S 3 /P 3 HT:PCBM/PEDOT:PSS/Ag. However, using the CBD method the oxidization of antimony sulfide can hardly be avoided, and thus antimony oxides formed create deep trap states on the surface, causing the serious recombination of photo-excited charge carriers.…”