A large–grain and highly crystalline Cu 3 BiS 3 thin film is successfully prepared by a dimethyl sulfoxide (DMSO)–based solution coating process . Without involving post sulfurization , Cu 3 BiS 3 absorber with grain size of ~ 1 µm has been achieved via a short-time drying of spin–coated precursor film on a hot plate at relatively low temperatures (< 300 °C). Our Cu 3 BiS 3 film exhibits a direct band gap of 1.47 eV with high absorption coefficients (~ 7 × 10 4 cm −1 ). Hall effect measurements reveal a p–type conductivity with hole concentration of ~ 10 16 cm −3 and mobility of 52.83 cm 2 /(V s). Moreover, an initial Cu 3 BiS 3 thin film solar cell with the device structure of glass/Mo/Cu 3 BiS 3 /CdS/ZnO/ITO/Al is fabricated, achieving a definite conversion efficiency of 0.17%. The mild preparation condition promises great potential of current method in realizing Cu 3 BiS 3 solar cells on temperature-sensitive substrates such as flexible polymer through an energy efficient way. The Cu 3 BiS 3 has thus been presented as a promising absorber material for solar cell applications.
Cu3BiS3 has been considered as an attractive photovoltaic material due to its suitable bandgap, excellent photoelectric properties, abundant component elements and low toxicity. However, most of the reported Cu3BiS3 solar cells contain toxic components in other functioning layers such as CdS in electron-transport layers (ETLs). In this study, the Cu3BiS3 thin films were prepared by spin-coating method. We find that the CuCl concentration in precursor solutions has influences on both the optical bandgap and grain size of the Cu3BiS3 thin films, thus affecting the performance of solar cells. The optimal CuCl concentration is 0.91 M. Besides, Al doped TiO2 (ATO) and MoOx films are employed as ETLs and hole-transport layers (HTLs) respectively, constructing a totally non-toxic thin film solar cell. Moreover, it is demonstrated that the ratio (RAl:Ti) of Al source (Aluminum nitrate nonahydrate) to Ti source [Titanium diisopropoxide bis(acetylacetonate)] in the precursor solution of ATO and the thickness of MoOx have significant influences on solar cells. Moderate Al doping in ATO, e.g. RAl:Ti=1:50, can produce oxygen vacancies and accelerate the interfacial charge transfer, thus resulting in the increased short-circuit current density and fill factor. With the optimized Cu3BiS3 absorber, ETL and HTL, improved cell performances are observed comparted to the spin-coated Cu3BiS3 counterparts with CdS as ETLs in literature.
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